Tag: Mānuka

Mānuka & Kānuka industry and research Hui

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In recent months I’ve been fortunate to attend two Hui (gatherings), involving researchers, industry and iwi representatives, focussed on two important native plants here in Aotearoa New Zealand, Mānuka (Leptospermum scoparium) & Kānuka (Kunzea ericoides).

Mānuka Hui

In June a two day Bioeconomy Science Institute (BSI) Maiangi Taiao Mānuka Hui attended by around 50 people was held at the Plant and Food (now Bioscience Research Institute) premises in Palmerston North. This was an inspiring event which brought together representatives of Māori groups and industry, with researchers from across all four of the previous Crown Research Institutes (CRI’s) and Callaghan Innovation, now combined into the new Bioeconomy Science Institute (BSI, or Maiangi Taiao. A handful of us had also taken part also in two previous hui on ‘Manuka and More’, held in 2016 in Ruatoria and Te Araroa on the east coast of New Zealand’s north island (Tairawhiti), which I wrote about at the time(1). 

Over the two day meeting, there were around 20 short presentations by researchers, industry and iwi representatives on some of the work done in recent years, involving our treasured native plant, Leptospermum scoparium (Mānuka).  It’s impossible to adequately summarise these presentations here, but quite a range of research projects have taken place or started within the past nine years. Much of this involves Mānuka Honey, given how important this industry  is now to many regions of Aotearoa, and how it was the first to put Mānuka on the global map(2).

Kānuka and Mānuka are the dominant native woody species forming early-successional vegetation on formerly forested sites in lowland New Zealand. Their importance as pioneer species has been shown by studies showing that species richness or subsequent biodiversity, was much better in areas where Kānuka and Mānuka were the initial prevalent species(3). A collaboration between Comvita and scientists from the Bioeconomy Science Institute has also demonstrated that planting Mānuka forests on former high-country marginal grazing land can significantly restore biodiversity in as little as five years(4).

The Mānuka honey industry went through a lengthy period of rapid growth in demand and hive numbers over several years prior to 2019. This became unsustainable however, and a range of factors lead to challenging times since then, with registered hive numbers falling sharply from a peak of 918,000 in 2019 to less than 490,000 in 2026. When I wrote about the 2016 Hui, hive numbers were around 350,000(1).

A great deal of evidence however, now suggests much rosier times lie ahead for the Mānuka honey industry. I’ve researched and written four review articles on the science behind this honey over the past 20 months, and the sheer volume and diversity of compelling research findings supporting its many health promoting and medicinal applications, is very encouraging(2, 5, 6, 7).

Jackie Evans and John Oliver from Comvita discussed work their company has been doing on the compound lepteridine, found only in Mānuka honey, recently shown to inhibit enzymes involved in gastrointestinal inflammation(8). A clinical trial involving lepteridine-standardized mānuka honey for the treatment of functional dyspepsia, is currently underway(9).

My talk was entitled “Mānuka – from Plant to Product”, and I spoke about my experience since 1998 with formulating and developing various herbal medicines for internal and topical use containing Mānuka honey, Mānuka oil, dried foliage, and hydroethanolic extracts. In this I incorporated some key issues to consider, when wanting to successfully develop and commercialise health products made using native plants.

Many other interesting presentations were made, including ongoing work into characterising the different genotypes within Mānuka, and methods to ensure better authenticity of Mānuka honey, and to distinguish it from Australian Leptospermum species. The need to preserve and protect mātauranga Māori (traditional Māori knowledge) and taonga species such as Mānuka through placing high value on the interweaving of relationships between people, places and the environment, was also a prominent theme throughout the hui.

A presentation by Grant Smith from the BSI was rather sobering though, as he discussed the continued advance of myrtle rust as a devastating pathogen on several of our other native Myrtaceae species such as ramarama and swamp maire. While others such as Mānuka, Kānuka, Pōhutukawa and rātā have yet to be seriously impacted, the damage this pathogenic fungus has caused to many native bush stands in parts of Australia, and increasing influence of extreme weather events and global warming, suggests a growing threat also to some of our iconic indigenous species(10). The work being done here on identifying mechanisms and genes associated with resistant varieties, may also help our Australian neighbours to better manage their own myrtle rust outbreaks.

At the start of the hui, David Chagne, Jenny Green and Nico Bordes gave an overview of the newly established BSI. Bringing the former CRI’s together again into a combined entity as the primary government agency involved in scientific and industrial research aimed at supporting the growth and resilience of the bioeconomy of New Zealand, makes absolute sense in my view.

Launch of the Bioeconomy Science Institute

Establishment and development of the Biodiscovery Platform, a $42 million government investment to support the development of high-value products and innovation over the next 7 years, was also discussed. This identified the shared sectors direction to build impactful fundable pathways, incorporating a fit for purpose, Treaty-based approach(11). The Biodiscovery Platform is in the process of setting priorities and exploring possible research partnerships. A key objective as a sector enabler is to invest in activities that bring groups together, and to establish clear, repeatable pathways for research into our native plants and their bioactivities and possible commercialisation pathways.

Kānuka Hui

A couple of months later in August, an inaugural hui dedicated to Kānuka (Kunzea ericoides), another highly endemic native species to Aotearoa, was put on by the Kānuka Charitable Trust (KCT), with support from the BSI. The Kānuka Charitable Trust was established in 2023 by a group of Māori landowners and business leaders to protect Kānuka as a taonga species and ensure Māori values guide the development of an emerging Kānuka industry, with Manu Caddie and Richard Manning as founding directors(12).

The hui was facilitated mostly by Nikki Harcourt and Manu Caddie, and attended by landowners, growers, essential oil producers, scientists and researchers and a range of people working with kanuka in their various companies and industries. While as with Mānuka these have to date been based almost entirely on essential oil and honey production, potential applications for other types of products or uses of this botanically related native tree, were discussed.

While ten years ago very little attention was given to Kānuka, it is an important species in forest regeneration. It has been widely planted on erosion-prone land, supports carbon sequestration, encourages biodiversity in flora and fauna, and contributes to rural employment.

Like its botanically related cousin Mānuka, it also possesses many medicinal properties. Traditional applications include for wounds and inflammatory skin conditions, and for several conditions affecting the digestive tract(13). 

Research within the last few years has shown antibacterial and antifungal activities for Kānuka oil against a range of organisms, including Propionibacterium acnes, and MRSA(14).  Its chemistry and relative bioactivities are variable depending on the location, season and extraction methods, but α-pinene is generally the most abundant compound.

Favourable results were reported from a 2022 clinical trial involving application of a 3% kānuka oil cream for eczema, funded by Hikurangi Bioactives, Honeylab and Callaghan Innovation(15). However, challenges have been encountered with commercialising this product in export markets, including unanticipated regulatory barriers in relation to being able to make therapeutic claims.

Authenticity work

Given some of the mistakes made by the Mānuka honey industry in the past, efforts to establish product authenticity are vital for the future Kānuka industry, in order to ensure product is true to label and to protect its market value and supplier reputation.

Much good work has been done and is underway in this area, particularly that by Nigel Perry from Plant & Food Research, on the phytochemistry and potential markers in Kānuka oil(16). David Speed from ALS Analytica, summarised ongoing studies into identification and characterisation of novel constituents of Kānuka, and distinguishing this from Australian Kunzea species. The monoterpene compound α-pinene is generally most prevalent in Kānuka oil, rather than the β-triketones characteristic of good quality Mānuka oil.

A talk by Sri Govindaraju of PAQ Laboratories, which provides specialist testing techniques to support the local honey industry, described how they have developed an assay method for Kānuka honey, and definitions for multifloral or monofloral honey. Currently a lot of blending of different honey suppliers is occurring, with the true volume of Kānuka honey being produced, is not being captured. The last two years had also seen low yields for Kānuka honey supplies, due to heavy rainfall during the short harvest season.

Kānuka honey was found to contain relatively high amounts of type-2 arabinogalactan proteins, which may contribute to immunostimulant and immunomodulatory properties(17).

Being able to further utilise natural waste products or normally discarded plant parts after harvest or extraction of their most desirable components, and fostering a more sustainable and circular economy, makes absolute sense in the world we live in today.  During extraction of the essential oil of Kānuka, large volumes of hydrosols, or aqueous preparations infused with mostly water soluble plant compounds, are produced. These also have many potential applications in human and animal health. Christel Brunschwig from the BSI discussed research into valorising the spent brush not only into hydrosols, but also as a potential biofuel source or feedstock for other types of processing or production operations.

Karl Fraser and Melissa Savage discussed work they are doing on environmental influences on Kānuka oil production, and an ecologist Meg Gray summarised the impact of cyclones, goats and deer grazing, and water quality, on the quality of a Kānuka forest. Pest control is now recognised as being crucial to avoid forest stagnation and loss of biodiversity, as well as the ability of a Kānuka forest to capture carbon.

Lessons learnt

I spoke about some of the lessons learnt from the Mānuka industry to date, and from my previous NHP industry experiences, including the hurdles and steps required to obtain product licences in Australia, and the importance of having a product development and commercialisation strategy that was fit for purpose. My talk also mentioned the importance of understanding regulatory requirements, as all too often these are not well considered, prior to investment in research and product commercialisation.

Another key message we heard at the hui, was that while stories concerning Kaupapa Māori and traditional knowledge are compelling and can support a global marketing strategy for products made from native plants, these need to be supported by collectivism, and consistency. Given the struggle that native plant based industries and companies in Aotearoa have had to date with attaining good and ongoing growth, yet beckoning and growing market opportunities in many overseas markets, this warrants much more consideration by some elements within the broader sector. In order to succeed with the sustainable, ethical and quality based commercialisation of natural health products manufactured using these indigenous plants, it is critical that producers of Mānuka and Kānuka work collectively to develop and support industry standards, certification, and consistent and adequately resourced research and marketing efforts.

References:

  1. Rasmussen PL. Mānuka and More. www.herbblurb.com November 18, 2016.
  2. Rasmussen PL. Mānuka and other Honeys – exciting recent research. www.herbblurb.com November 30, 2024.
  3. Sullivan Jon J, Williams Peter A, Timmins SM. (2007) Secondary forest succession differs through naturalised gorse and native kānuka near Wellington and Nelson. New Zealand Journal of Ecology 31(1): 22 – 38©New Zealand Ecological Society.
  4. https://www.bioeconomyscience.co.nz/news-and-events/news/2026-news/biodiversity-benefits-of-large-scale-manuka-forest-planting
  5. Rasmussen PL, Manuka honey as a medicine. New Zealand Doctor, 15 February 2025. ISSN
  6. Rasmussen PL. Honey as a medicine: Special properties of mānuka honey. Pharmacy Today, 1 October 2024, published by The Health Media Ltd, Auckland, ISSN 1170-1927.
  7. Rasmussen PL. Mānuka honey shows promise in cancer prevention and as treatment adjunct. 1 December 2024, published by The Health Media Ltd, Auckland, ISSN 1170-1927.
  8. Lin B, Nair S, Fellner DMJ, Nasef NA et al, The Leptospermum scoparium (Mānuka)-Specific Nectar and Honey Compound 3,6,7-Trimethyllumazine (LepteridineTM) That Inhibits Matrix Metalloproteinase 9 (MMP-9) Activity. Foods. 2023 Nov 9;12(22):4072. 
  9. Ombasa L, Miller J, Ware L, Abbotts-Holmes H et al, Impact of Mānuka Honey on Symptoms and Quality of Life in Individuals With Functional Dyspepsia: Protocol for a Feasibility Randomized Controlled Trial. JMIR Res Protoc. 2025 May 21;14:e66417.
  10. Rasmussen PL. Mānuka and Myrtle Rust. www.herbblurb.com July 19, 2017.
  11. https://www.mbie.govt.nz/about/news/government-launches-biodiscovery-platform-to-grow-new-zealands-bioeconomy.
  12. https://www.hakanuka.co.nz/
  13. Rasmussen PL, Kānuka & Inflammation. Phytomed Medicinal Herbs Ltd, Dec 2022. https://www.phytomed.co.nz/blogs/phytobrief/kanuka-inflammation.
  14. Haira TH, Ooi RJ, Pay RA, Paenga B, Caddie M, Skinner D, Harcourt N, Jackson M, Keyzers RA, Munkacsi AB. Antimicrobial-guided metabolomic analysis of essential oil derived from the Aotearoa New Zealand endemic plant Kunzea robusta (Kānuka). Fitoterapia. 2025 Jul;184:106592.
  15. Shortt N, Martin A, Kerse K, Shortt G et al, Medical Research Institute of New Zealand’s Pharmacy Research Network. Efficacy of a 3% Kānuka oil cream for the treatment of moderate-to-severe eczema: A single blind randomised vehicle-controlled trial. EClinicalMedicine. 2022 Jul 15;51:101561.
  16. Perry N. Kanuka oil: current knowledge and potential markers. Plant & Food Research Dunedin, October 2022

Mānuka and other Honeys – exciting recent research

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Honey as a medicine

Honey has been prized both as a food and medicine since the earliest times.(1,2)  Traditional medicine practices from around the world have long valued its therapeutic properties, particularly as a remedy for burns, cataracts, ulcers and wound healing.

All honeys are rich in antioxidant, anti-inflammatory and antimicrobial flavonoids, phenolic acids and other bioactive compounds cleverly extracted and manufactured by bees. These contribute to honey’s anti-inflammatory, antibacterial, antiviral, immunomodulatory and anti-allergic activities.(3-5)

While applications for wound care have become quite well known, clinical trials have also reported beneficial effects of honey intake on cardiovascular and metabolic risk factors, glucose tolerance, mucositis caused by chemo-radiotherapy, and coughs in children.(6,7)

Different types of honey are classified depending on the floral source and/or the geographical regions from which they derive.

Mānuka honey

Mānuka honey is honey made by bees using nectar from flowers of Leptospermum scoparium, a small native tree which grows abundantly throughout Aotearoa New Zealand. Mānuka is an important plant in rongoā Māori and for medical herbalists here, with its bark, foliage and seeds used to compound preparations for wounds, cuts, sores and skin diseases, colds, coughs and gastrointestinal conditions.(8,9) Its essential oil, also has multiple anti-inflammatory, antimicrobial and other bioactivities.(10)

Apart from being a rich source of glucose, fructose and flavonoids such as quercetin and chrysin found in other honeys, Mānuka honey contains unique chemical compounds such as methylglyoxal (MGO), dihydroxyacetone, leptosperin glyoxal, methyl syringate and leptosin.(11)

While once regarded as being inferior to other culinary honeys in terms of its taste profile, interest in the medicinal properties of Mānuka honey began to grow during the 1980’s. Its reputation as a health promoting food grew rapidly, a key catalyst being research in the early 1980’s which showed Mānuka honey to have potent antibacterial activities. 

Antimicrobial properties

These were reported against a wide range of different human pathogens, but antibacterial properties against Staphylococcus aureus and the gut pathogen Helicobacter pylori, attracted particular interest for Mānuka honey.(11-14) With stomach problems being a common human complaint, this research together with anecdotal reports of improvement in various gastrointestinal problems when taking Mānuka honey, lead to increasing demand.

Mānuka honey impregnated dressings have been developed and shown to be effective in wound care and infection management. Successful applications include for diabetic and venous leg ulcers(16-18) and hospital acquired pressure injuries in critically ill children.(19)  These dressings are now being increasingly used by wound care nurse practitioners in Aotearoa New Zealand.

On a global level, much research is ongoing into the antibacterial activities of Mānuka and other honeys.  Numerous scientific papers involving the potential infection control and antimicrobial activities of Mānuka honey have been published over the past year, with several encouraging findings.(20-26)

Research into the use of medical grade Mānuka honey as a post surgical wound application also continues in a number of countries outside of Aotearoa New Zealand, with encouraging findings.(28-30) Applications in oral surgery and dentistry, are also receiving increased attention.(31, 32)

Mānuka honey at low concentrations has been reported to kill multidrug-resistant and extensively drug-resistant clinical strains of Salmonella Typhi.(22)  Saudi Arabian researchers have also reported activity against carbapenem-resistant Enterobacterales.(21)  Medical researchers in Sweden, have found topical Mānuka honey to reduce the bacterial count of Staphylococcus aureus in a comparable way to an intramuscular antibiotic.(33)  They have also advocated potential applications for Mānuka honey as an immediate treatment for war wounds in the field of combat.

 A clinical trial to compare the use of a medical grade honey with the antifungal drug fluconazole for vaginal thrush is currently underway in the Netherlands, and the results will be interesting.(34)

Honey and Cancer

With rates of cancer increasing steadily as the global population increases and people live longer, research into interventions to help reduce the treatment burden has become more compelling. Interest in potential applications of honey in cancer therapy go back a long way. In fact there are now more than 800 papers and several reviews on honey and cancer in the scientific literature, many with encouraging findings.(35-42)

In vitro antiproliferative and apoptotic effects for honey have been reported against a large number of different cancer cell types. These include bladder cancer, colon, melanoma, breast, cervical, oral, prostate, hepatic and osteosarcoma cancer.  Several different honey types including Mānuka, thyme, gelam and acacia honeys, have shown such activities.(43-50) Relevant activities have also been reported in studies involving rat and mice models of different forms of cancer, including breast, colon, bladder and Ehrlich Ascite carcinoma.(46, 47, 51-54)

Mānuka Honey & cancer

Potential applications of Mānuka preparations in cancer patients, were first reported for a gargle using a mix of mānuka and kānuka essential oils diluted in water, bringing relief to mucositis of the oropharyngeal area as a result of radiation treatment for head and neck cancers.(55)

In vitro research by a number of different researchers has found anti-proliferative effects of Mānuka honey on breast, colorectal, breast and melanoma cell lines. Researchers from United Arab Emirates found that Mānuka honey had potent on all three cancer cell lines in a time- and dose-dependent manner, and was effective at concentrations as low as 0.6% (w/v).(53, 54)

They’ve also found improved survival rates of mice with melanoma when Mānuka honey was administered as an injection, alongside treatment with the chemotherapy drug paclitaxel.(53) Subject to future parenteral product development and human clinical studies, this study suggests exciting potential applications as an adjunct in cancer chemotherapy.  

Enhanced anti-tumour responses against colorectal cancer in mice have been shown following oral administration of Mānuka honey over a four week period.(56) These effects were correlated with immunomodulatory activities and changes in the gut microbiota.

In 2017, Malaysian researchers reported inhibitory effects on tumour development for Mānuka and Tualang honeys in a rat model of breast cancer.(57)  Recently American researchers have also revealed inhibitory effects on human breast cancer progression in preclinical models for Mānuka honey. Mānuka honey reduced the proliferation of MCF-7 breast cancer cells but not that of non-malignant human mammary epithelial cells. Antitumor activity was in a similar range to that exerted by treatment of MCF-7 cells with the oestrogenic antagonist tamoxifen, widely used in the management of breast cancer. (58)

An Italian team has undertaken a considerable amount of research into Mānuka honey’s potential preventive effects against colon cancer. They reported strong inhibitory effects on human colon cancer cells in a dose-dependent manner.(59)  Anti-metastatic impacts on colon cancer stem-like cells, a reduction in the ability of colorectal cancer cells to migrate, and downregulation of pro-angiogenic factors, were revealed as likely mechanisms of Mānuka honey’s activity.(60, 61, 62)

Possible protective effects against prostate cancer cell metastases, have been reported for New Zealand thyme, mānuka and honeydew honeys. Both their phenolic and sugar components, were shown to reduce the cellular adhesion abilities of cancer cells, in this in vitro study.(63)

With these types of cancers having a high risk of metastases, while clinical studies are needed, these anti-metastatic effects of Mānuka honey, offer much promise.

Mechanisms of action

Several potential mechanisms of action are evident for potential preventive effects of Mānuka honey against cancer development. Oxidative stress and increased levels of free radicals is involved in cancer formation, and Mānuka honey is rich in antioxidant phenolic acids and polyphenols with in vitro antiproliferative activity against several types of cancer.(41, 54)

A low immune status is well known to increase the risk of cancer development. Italian research showing an ability of Mānuka honey to modulate the immune system by inducing immunostimulatory and anti-inflammatory effects, could potentially help with chemoprevention.(64)  It’s antimicrobial actions may also be useful, given that chronic infections such as Epstein-Barr virus, human papilloma virus and Helicobacter pylori, are also associated with a higher risk of cancer development.

Possible Chemotherapy adjunct?

Recent research involving an international team of researchers, has provided evidence of sensitising effects of Mānuka honey to chemotherapy  against colon cancer cells.(62) Mānuka honey was associated with downregulation of pro-angiogenic factors, and enhanced the cytotoxicity of 5-fluorouracil. This and other studies by the Italian team suggest a potential of Mānuka honey as an adjunctive intervention to increase the efficacy of this and potentially other anticancer drugs against colon cancer cells.(59, 61, 62)

Protective effects of honey against cisplatin-induced renal toxicity, has been shown both in animals and in patients with cancer.(65)  A recent review found significant evidence for an ability of honey to mitigate toxicity from anticancer chemotherapy toxicity, with multiple mechanisms for this being evident. These included inhibition of oxidative stress and NF-κB-mediated inflammation, the dampening of caspase-dependent apoptosis cascades, and several other potential molecular mechanisms.(42)  

Oral mucositis

Oral mucositis (stomatitis) is a serious complication of cancer chemotherapy resulting in pain, an inability to eat or drink, and often weight loss. It occurs in a large proportion of paediatric patients being treated for cancer, and in patients undergoing treatment with radiotherapy or chemotherapy for head, neck and breast cancers, and is difficult to treat in clinical practice.

At least fifteen clinical trials have now taken place involving Mānuka and several other honey types from around the world as an oral application for oral mucositis, with most finding positive results.(66-69) These include a clinical trial using Mānuka honey in children with leukaemia suffering from chemotherapy-induced oral mucositis.(70)

Summary

Honey is a natural product used since ancient times for its nutritive and therapeutic value.  Despite this extensive history, and a huge body of laboratory data now implicating its usefulness for a large number of serious health conditions in humans, clinical applications have been limited until recently, by there being few human trials, and widespread variability in honey quality.

Research is increasingly providing compelling evidence for preventative as well as potential clinical applications of different types of Mānuka honey, in modern medicine. This research, mostly undertaken outside of Aotearoa New Zealand, suggests exciting therapeutic value particularly in the management of infectious disease and cancer, both highly prevalent and expensive conditions which have a high burden on patients and healthcare systems.

Aotearoa New Zealand was the first country in the world to successfully produce and commercialise grades of honey suitable to be prescribed and sold or dispensed for serious medical conditions. Several other countries are now developing or have already developed their own medical honeys, and are putting these through clinical trials for a range of conditions.

In order to retain and further build Aotearoa New Zealand’s international reputation as a country producing some unique health promoting honeys, significant investment and a world class regulatory environment is needed. Therapeutic claims should be legally possible for products which have achieved clinical trial validation and meet quality standards. Without this, further innovation and product development may be compromised, while other countries forge ahead with developments, in what is certain to continue to be a growing global industry.

Given the extent of the many promising preclinical findings into the potential of Mānuka and other honeys to improve outcomes in cancer patients, more controlled clinical studies are needed. They should involve further work on animal models of cancer, as well as pilot clinical studies using phytochemically characterised types of honey, as an adjunctive treatment in patients receiving chemotherapy or radiotherapy.(9)

While much of the Mānuka honey industry here has gone through difficult times in the aftermath of Covid-19 and challenges in export markets, new and ongoing research suggests there is much more to this treasured local natural product, than just its value as a food.

References:

  1. Zaidi, M. Z., & Sharma, J. (2019). Honey and its beneficial therapeutic effects: A review. Journal of Pharmacognosy and Phytochemistry, 8(4), 1056-1061.
  2. Nikhat S, Fazil M. History, phytochemistry, experimental pharmacology and clinical uses of honey: A comprehensive review with special reference to Unani medicine. J Ethnopharmacol. 2022 Jan 10;282:114614. 
  3. Aw Yong PY, Islam F, Harith HH, Israf DA, Tan JW, Tham CL. The Potential use of Honey as a Remedy for Allergic Diseases: A Mini Review. Front Pharmacol. 2021 Jan 26;11:599080
  4. Jodidio M, Schwartz RA. Honey therapies for dermatological disorders: more than just a sweet elixir. Int J Dermatol. 2024 Apr;63(4):422-430. 
  5. Khataybeh B, Jaradat Z, Ababneh Q. Anti-bacterial, anti-biofilm and anti-quorum sensing activities of honey: A review. J Ethnopharmacol. 2023 Dec 5;317:116830.
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  7. Abuelgasim H, Albury C, Lee J. Effectiveness of honey for symptomatic relief in upper respiratory tract infections: a systematic review and meta-analysis. BMJ Evid Based Med. 2021 Apr;26(2):57-64.
  8. Rasmussen PL, Manuka (Leptospermum scoparium) – A Review. Phytonews 1, September 1998, published by Phytomed Medicinal Herbs Ltd, Auckland, New Zealand.    ISSN 1175-0251.
  9. Riley Murdoch, Maori Healing and Herbal, published by Viking Sevenseas, Paraparaumu, New Zealand, 1994
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  11. Wang S, Qiu Y, Zhu F. An updated review of functional ingredients of Manuka honey and their value-added innovations. Food Chem. 2024;440:138060.
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  13. Willix DJ, Molan PC, Harfoot CG. A comparison of the sensitivity of wound-infecting species of bacteria to the antibacterial activity of manuka honey and other honey. J Appl Bacteriol. 1992 Nov;73(5):388-94
  14. al Somal N, Coley KE, Molan PC, Hancock BM. Susceptibility of Helicobacter pylori to the antibacterial activity of manuka honey. J R Soc Med. 1994 Jan;87(1):9-12. PMID: 8308841; PMCID: PMC1294271.
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  16. Shan Y. Medicinal honey in clinical practice: viable alternative or useful adjunct in wound care management? Br J Nurs. 2019 Jun 27;28(12):S23-S30.
  17. Gethin G, Cowman S. Bacteriological changes in sloughy venous leg ulcers treated with manuka honey or hydrogel: an RCT. J Wound Care. 2008 Jun;17(6):241-4, 246-7. 
  18. Kamaratos AV, Tzirogiannis KN, Iraklianou SA, Panoutsopoulos GI, Kanellos IE, Melidonis AI. Manuka honey-impregnated dressings in the treatment of neuropathic diabetic foot ulcers. Int Wound J. 2014 Jun;11(3):259-63
  19. Sankar J, Lalitha AV, Rameshkumar R, Mahadevan S, Kabra SK, Lodha R. Use of Honey Versus Standard Care for Hospital-Acquired Pressure Injury in Critically Ill Children: A Multicenter Randomized Controlled Trial. Pediatr Crit Care Med. 2021 Jun 1;22(6):e349-e362.
  20. Onyango LA, Liang J. Manuka honey as a non-antibiotic alternative against Staphylococcus spp. and their small colony variant (SCVs) phenotypes. Front Cell Infect Microbiol. 2024;14:1380289
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  22. Bashir I, Rasool MH, Shafique M, Jabeen K, Qamar MU. Exploring the antimicrobial efficacy of Manuka honey against multidrug-resistant and extensively drug-resistant Salmonella Typhi causing septicemia in Pakistan. Future Microbiol. Published online August 7, 2024. 
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  37. Erejuwa OO, Sulaiman SA, Wahab MS. Effects of honey and its mechanisms of action on the development and progression of cancer. Molecules. 2014 Feb 21;19(2):2497-522
  38. Subramanian AP, John AA, Vellayappan MV, Balaji A, Jaganathan SK, Mandal M, Supriyanto E. Honey and its phytochemicals: Plausible agents in combating colon cancer through its diversified actions. Journal of Food Biochemistry. 2016 Aug;40(4):613-29.
  39. Waheed M, Hussain MB, Javed A, Mushtaq Z, Hassan S, Shariati MA, Khan MU, Majeed M, Nigam M, Mishra AP, Heydari M. Honey and cancer: A mechanistic review. Clin Nutr. 2019 Dec;38(6):2499-2503
  40. Eteraf-Oskouei T, Najafi M. Uses of Natural Honey in Cancer: An Updated Review. Adv Pharm Bull. 2022 Mar;12(2):248-261.
  41. Jaganathan SK, Mandal M. Antiproliferative effects of honey and of its polyphenols: a review. J Biomed Biotechnol. 2009;2009:830616. 
  42. Bose D, Famurewa AC, Akash A, Othman EM. The Therapeutic Mechanisms of Honey in Mitigating Toxicity from Anticancer Chemotherapy Toxicity: A Review. J Xenobiot. 2024 Aug 20;14(3):1109-1129.
  43. Gribel’ NV, Pashinskiĭ VG. Protivoopukholevye svoĭstva meda [The antitumor properties of honey]. Vopr Onkol. 1990;36(6):704-9. Russian.
  44. Kassi E, Chinou I, Spilioti E, Tsiapara A, Graikou K, Karabournioti S, Manoussakis M, Moutsatsou P. A monoterpene, unique component of thyme honeys, induces apoptosis in prostate cancer cells via inhibition of NF-κB activity and IL-6 secretion. Phytomedicine. 2014 Sep 25;21(11):1483-9. 
  45. Badolato M, Carullo G, Cione E, Aiello F, Caroleo MC. From the hive: Honey, a novel weapon against cancer. Eur J Med Chem. 2017 Dec 15;142:290-299.
  46. Hegazi NM, Elghani GEA, Farag MA. The super-food Manuka honey, a comprehensive review of its analysis and authenticity approaches. J Food Sci Technol. 2022 Jul;59(7):2527-2534.
  47. Ahmed S, Othman NH. The anti-cancer effects of Tualang honey in modulating breast carcinogenesis: an experimental animal study. BMC Complement Altern Med. 2017 Apr 11;17(1):208.
  48. Kadir EA, Sulaiman SA, Yahya NK, Othman NH. Inhibitory effects of Tualang Honey on experimental breast cancer in rats: a preliminary study. Asian Pac J Cancer Prev. 2013;14(4):2249-54.
  49. Kocyigit A, Aydogdu G, Balkan E, Yenigun VB, Guler EM, Bulut H, Koktasoglu F, Gören AC, Atayoglu AT. Quercus pyrenaica Honeydew Honey With High Phenolic Contents Cause DNA Damage, Apoptosis, and Cell Death Through Generation of Reactive Oxygen Species in Gastric Adenocarcinoma Cells. Integr Cancer Ther. 2019 Jan-Dec;18:1534735419876334. 
  50. Fauzi AN, Norazmi MN, Yaacob NS. Tualang honey induces apoptosis and disrupts the mitochondrial membrane potential of human breast and cervical cancer cell lines. Food Chem Toxicol. 2011 Apr;49(4):871-8. doi: 10.1016/j.fct.2010.12.010.
  51. Swellam T, Miyanaga N, Onozawa M, Hattori K, Kawai K, Shimazui T, Akaza H. Antineoplastic activity of honey in an experimental bladder cancer implantation model: in vivo and in vitro studies. Int J Urol. 2003 Apr;10(4):213-9. doi: 10.1046/j.0919-8172.2003.0060
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  53. Fernandez-Cabezudo MJ, El-Kharrag R, Torab F, Bashir G, George JA, El-Taji H, al-Ramadi BK. Intravenous administration of manuka honey inhibits tumor growth and improves host survival when used in combination with chemotherapy in a melanoma mouse model. PLoS One. 2013;8(2):e55993. 
  54. Idriss I, Ali AH, Alam A, Fernandez-Cabezudo M, Ayyash M, Al-Ramadi BK. Differential in vitro cytotoxic effects and metabolomic insights into raw and powdered Manuka honey through UPLC-Q-TOF-MS. Sci Rep. 2024 Jul 30;14(1):17551. D
  55. Maddocks-Jennings W, Wilkinson JM, Cavanagh HM, Shillington D. Evaluating the effects of the essential oils Leptospermum scoparium (manuka) and Kunzea ericoides (kanuka) on radiotherapy induced mucositis: a randomized, placebo controlled feasibility study. Eur J Oncol Nurs. 2009 Apr;13(2):87-93.
  56. Masad RJ, Idriss I, Mohamed YA, Al-Sbiei A, Bashir G, Al-Marzooq F, Altahrawi A, Fernandez-Cabezudo MJ, Al-Ramadi BK. Oral administration of Manuka honey induces IFNγ-dependent resistance to tumor growth that correlates with beneficial modulation of gut microbiota composition. Front Immunol. 2024 Feb 20;15:1354297.
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  58. Márquez-Garbán DC, Yanes CD, Llarena G, et al. Manuka Honey Inhibits Human Breast Cancer Progression in Preclinical Models. Nutrients. 2024;16(14):2369.
  59. Afrin S , Giampieri F , Gasparrini M , Forbes-Hernández TY , Cianciosi D , Reboredo-Rodriguez P , Amici A , Quiles JL , Battino M . The inhibitory effect of Manuka honey on human colon cancer HCT-116 and LoVo cell growth. Part 1: the suppression of cell proliferation, promotion of apoptosis and arrest of the cell cycle. Food Funct. 2018 Apr 25;9(4):2145-2157.
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  61. Cianciosi D, Armas Diaz Y, Alvarez-Suarez JM, Chen X, Zhang D, Martínez López NM, Briones Urbano M, Quiles JL, Amici A, Battino M, Giampieri F. Can the phenolic compounds of Manuka honey chemosensitize colon cancer stem cells? A deep insight into the effect on chemoresistance and self-renewal. Food Chem. 2023 Nov 30;427:136684.
  62. Cianciosi D, Forbes-Hernández TY, Regolo L, Alvarez-Suarez JM, Quinzi D, Sargenti A, Bai W, Tian L, Giampieri F, Battino M. Manuka honey in combination with 5-Fluorouracil decreases physical parameters of colonspheres enriched with cancer stem-like cells and reduces their resistance to apoptosis. Food Chem. 2022 Apr 16;374:131753. 
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  64. Gasparrini M, Afrin S, Forbes-Hernández TY, Cianciosi D, Reboredo-Rodriguez P, Amici A, Battino M, Giampieri F. Protective effects of Manuka honey on LPS-treated RAW 264.7 macrophages. Part 2: Control of oxidative stress induced damage, increase of antioxidant enzyme activities and attenuation of inflammation. Food Chem Toxicol. 2018 Oct;120:578-587.
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New Zealand Native plants for gastrointestinal conditions, and their influences on the gut microbiome

On By HerbBlurbIn Uncategorized2 Comments

Introduction

Many of our native plant medicines have the ability to help in the management of conditions affecting the gastrointestinal tract(1). While these have diverse actions and undoubtedly act on many levels concomitantly to prevent and treat such conditions, their direct effects on the gut microbiome, are likely to be contributory.

The gut microbiome is an intricate and dynamic ecosystem of microbes that is strongly influenced by our environment, diet and genes, and altering it can significantly influence our predisposition to and outcomes from many illnesses. While these extend way beyond gastrointestinal conditions alone(2,3), the association between modulation of the gut microbiome and digestive health, is of particular interest.

Furthermore, it is these intestinal microbiota that play an important role in both the activation and metabolism of medicinal plant phytochemicals themselves, just as they break down proteins, carbohydrates and fats in foods, to simpler and bioavailable molecules. A diverse and healthy microbiome is thus conducive to ensuring optimal processing and bioavailability of medicinally active phytochemicals, and thus achieving favourable clinical outcomes in phytotherapy.

Probiotics (live microorganisms that when administered in adequate amounts confer a health benefit) are now highly regarded, but we’re also increasingly learning about the important role of prebiotics, in feeding and selectively promoting probiotic growth and human health. These include plant foods such as psyllium, onion, asparagus, garlic, kumara, chicory, Jerusalem artichoke, bananas, beetroot and oats, which provide complex carbohydrates such as inulin and other beneficial fibres to support a healthy gut microbiota and immune system.  Additionally, there seem to be positive contributions made by other specific primary or secondary components of many plants and mushrooms, to the microbiome community and subsequently to health outcomes.

Native plants and the microbiome

Regular ingestion of various herbal teas including green, kuding and baical skullcap teas can exert beneficial effects on the gut microbiota, including an increased number of unique bacterial genera, and changes in the relative abundances of particular species(4-6). Catechins and insoluble fibre contribute to these benefits, and exert a prebiotic-like effect on gut microbiota(7). Supplementation with certain tannins has also been found to increase the diversity and abundance of butyrate-producing and probiotic bacteria and metabolism of amino acids(8). In fact the antioxidant and disease preventative properties of many polyphenolic rich plants, may correlate to some extent with their effects on gut bacterial species(9).

While research is required, many native plants from Aotearoa New Zealand are very rich in a diverse range of polyphenolic compounds and are likely to also produce similar benefits. While tannins and other larger ones of these have poor oral bioavailability, they can nevertheless facilitate significant changes in the abundance of bacterial species associated with a wide range of health outcomes. The hydrolysis of tannins and flavonoids by gut microbiota is also being increasingly recognised as producing smaller, bioavailable and bioactive metabolites, with many health benefits(10, 11).

Controlling infections

Antibiotics are widely used to eradicate unwanted bacteria, yet they are generally not very selective, and often produce serious negative impacts on beneficial bacteria and the gut microbiome(12). Plants with a narrower spectrum of antimicrobial activity and when carefully combined, have the ability to provide a more targeted action, and thus reduced adverse events(13).   They should therefore be used more as first line treatments for many types of infection, and more research into this as well as their combined use with antibiotics, is urgently needed.

The microbiota is also involved in reducing and preventing colonization by enteric pathogens through the process of competitive exclusion and the production of antimicrobial substances. Plants that enhance this production of bacteriostatic and bactericidal substances by the microbiota, are therefore potential interventions to deal with some pathological infections(14).

Mānuka (Leptospermum scoparium), Kānuka (Kunzea ericoides), Harakeke (Phormium tenax), Horopito (Pseudowintera colorata), Tanekaha (Phyllocladus trichomanoides), Rewarewa (Knightia excelsa) Totara (Podocarpus totara, Rimu (Dacrydium cupressinum) and Pukatea (Laurelia novae-zelandiae), all exhibit good activity against specific pathogens. 

Animal studies are increasingly showing the microbiome to have a positive impact not only on gut physiology, but also the immune system of the host. Part of the mechanism of Echinacea purpurea’s immunomodulatory effects may involve its influences on the gut microbiota, as shown by improvement in immunosuppressed ducks in conjunction with increased abundance of beneficial intestinal bacteria(15).

Antibacterial and antifungal actions are prominent activities of many native plants, and traditional uses for gastrointestinal tract infections, were once common. Tannin rich native species such as Mānuka can treat dysentery and diarrhoea, and most tannins also have intrinsic antibacterial properties. The powerful astringent and antimicrobial effects produced by infusions and hydroethanolic liquid extracts of Mānuka’s leaves and stems, make it a useful component of a treatment for gastrointestinal infections.

In its living state, Mānuka itself has around 200 different bacteria within its leaves, stems and roots, that make up a rich community of endophytes (microorganisms that live within and near plants, in a symbiotic relationship). Several of these bacteria themselves produce antifungal or antibacterial compounds as part of their competitive survival(16). Ingestion of preparations made from its leaves and stems will deliver a range of phytochemicals with the potential to modulate the gut microbiome, and thus provide digestive system benefits. The often symbiotic relationships between endophytes and plants, and those between microbes and humans, appear to have much in common.

Koromiko (Hebe stricta) is another effective remedy used for diarrhoea and dysentery among Māori and European settlers, including by New Zealand soldiers during the Second World War. Rebalancing of different microbial species within the gut, is probably involved in its antidiarrhoeal and anti-inflammatory properties.

Intestinal mucosa tonics

Damage to the integrity of the intestinal biofilm can result in alteration in intestinal permeability, a condition widely described asleaky gut. When this occurs, the immune system can become weak or dysregulated, making conditions such as irritable bowel syndrome or inflammatory bowel disease more likely(17). Ulcerative colitis, Crohns and irritable bowel syndrome are all associated with enhanced secretion of proinflammatory cytokines, poor maintenance of the epithelial barrier, and gut dysbiosis(18, 19).

Kawakawa (Piper excelsum) is a plant widely used for gastrointestinal inflammation and has many pronounced digestive system benefits(20, 21). As with other Piperaceae species, influences on gastrointestinal absorption and gut permeability, and vascular barrier protective effects have been shown for Kawakawa and some of its amide constituents, including pellitorine, piperine and piperdardine(22, 23).  Lignans are also prominent constituents, and given other lignans are known to interact with gut microbiota, microbiomal modulations through these phytochemicals within Kawakawa, may also take place.

Other plants with broad-ranging effects on the digestive system, are Horopito (Pseudowintera colorata) and Akeake (Dodonaea viscosa). Both plants exhibit astringent, anti-inflammatory and some antimicrobial properties which probably impact population levels of some microbiome species in a negative manner, and others in a potentially facilitatory manner. An Indian variety of Dodonaea viscosa has been shown to be gastroprotective in animal studies(24), suggesting a potentially useful role in the management of peptic ulcers(25).

Polysaccharides

These are another type of secondary metabolite whose oral bioavailability is limited, but are increasingly being recognized for the complex interactions they have with microbes within the gut. These include modulation of the gut microbiota composition itself, metabolism of polysaccharides to short chain fatty acids, and polysaccharide-induced modulation of the production of gut microbiota metabolites such as trimethylamine, tryptophan and lipopolysaccharides(26). The widely used Psyllium husk (Plantago ovata), increases faecal water content and improves constipation while increasing populations of butyrate-producing microbiota(27). Amelioration of antibiotic-associated diarrhoea has been associated with  a prebiotic effect of polysaccharides from the medicinal fungus Hoelen (Poria cocos)(28).

Hoheria (Hoheria populnea), is a native tree whose various different organs are all rich in polysaccharides.  Like Slippery Elm and other polysaccharide hydrocolloid rich plants, Hoheria can help reduce symptoms of dyspepsia or gastritis when taken either as an infusion or hydroethanolic liquid extract. As with many other polysaccharide-rich plants or medicinal fungi, beneficial effects on the gut microbiome, also seem likely.

Bitters

Medical herbalists are generally taught that it is the stimulatory effects of bitter-tasting plants on every component of the gastrointestinal system, which accounts for their many beneficial and tonic like actions on digestive processes and thus overall health. We now also know that activation of bitter receptors is involved in the regulation of appetite, insulin sensitivity, airway innate immunity, and other physiological processes. The ability of bitter tasting plants and their inclusion in the diet or regular herbal tonics to positively influence the gut microbiome community, is being increasingly revealed(29-31).

Native plants such as Kohekohe (Dysoxylum spectabile) and Tanekaha make excellent bitter substitutes to classical European bitters such as Gentian and Wormwood.  These are also likely to have complex but beneficial actions on the gut microbiome.

Summary

Humans have a wide variation in the makeup of their gut microbiome.  This potentially results in variations in microbial metabolism of many phytochemicals, and thus the resulting therapeutic activities of medicinal plants. The relationships between plants and microbes works in both directions though, and there are a multitude of ways in which the ingestion of many plants can produce health benefits through influencing the functions of these bacteria found without our gastrointestinal tract.

While we are only just starting to understand elements of the complex human gut microbiome, it seems certain to provide innovative targets for the incorporation of plants native to Aotearoa New Zealand, to help prevent and treat several gastrointestinal conditions.

References:

  1. Rasmussen PL. Treating digestive conditions using New Zealand native plants. Phytomed seminar, October 2009.
  2. Miyauchi E, Shimokawa C, Steimle A, Desai MS, Ohno H. The impact of the gut microbiome on extra-intestinal autoimmune diseases. Nat Rev Immunol. 2023;23(1):9-23
  3. Sasso JM, Ammar RM, Tenchov R, et al. Gut Microbiome-Brain Alliance: A Landscape View into Mental and Gastrointestinal Health and Disorders. ACS Chem Neurosci. 2023;14(10):1717-1763.
  4. Morishima, S., Kawada, Y., Fukushima, Y., Takagi, T., Naito, Y., & Inoue, R. (2023). A randomized, double-blinded study evaluating effect of matcha green tea on human fecal microbiota. Journal of clinical biochemistry and nutrition, 72(2), 165–170.
  5. Vamanu E, Dinu LD, Pelinescu DR, Gatea F. Therapeutic Properties of Edible Mushrooms and Herbal Teas in Gut Microbiota Modulation. Microorganisms. 2021;9(6):1262. 
  6. Shen J, Li P , Liu S , et al. The chemopreventive effects of Huangqin-tea against AOM-induced preneoplastic colonic aberrant crypt foci in rats and omics analysis [published correction appears in Food Funct. 2021 Mar 15;12(5):2336-2337.
  7. Thumann, T. A., Pferschy-Wenzig, E. M., Aziz-Kalbhenn, H., Ammar, R. M., Rabini, S., Moissl-Eichinger, C., & Bauer, R. (2020). Application of an in vitro digestion model to study the metabolic profile changes of an herbal extract combination by UHPLC-HRMS. Phytomedicine : international journal of phytotherapy and phytopharmacology, 71, 153221.
  8. Correa PS, Mendes LW, Lemos LN, et al. Tannin supplementation modulates the composition and function of ruminal microbiome in lambs infected with gastrointestinal nematodes. FEMS Microbiol Ecol. 2020;96(3):fiaa024.
  9. Morisette A, Kropp C, Songpadith JP, et al. Blueberry proanthocyanidins and anthocyanins improve metabolic health through a gut microbiota-dependent mechanism in diet-induced obese mice. Am J Physiol Endocrinol Metab. 2020;318(6):E965-E980.
  10. Sallam IE, Abdelwareth A, Attia H, et al. Effect of Gut Microbiota Biotransformation on Dietary Tannins and Human Health Implications. Microorganisms. 2021;9(5):965.
  11. Marín L, Miguélez EM, Villar CJ, Lombó F. Bioavailability of dietary polyphenols and gut microbiota metabolism: antimicrobial properties. Biomed Res Int. 2015;2015:905215.
  12. Patangia DV, Anthony Ryan C, Dempsey E, Paul Ross R, Stanton C. Impact of antibiotics on the human microbiome and consequences for host health. Microbiologyopen. 2022;11(1):e1260.
  13. Chou, S., Zhang, S., Guo, H., Chang, Y. F., Zhao, W., & Mou, X. (2022). Targeted Antimicrobial Agents as Potential Tools for Modulating the Gut Microbiome. Frontiers in microbiology, 13, 879207.
  14. Clavijo, V., & Flórez, M. J. V. (2018). The gastrointestinal microbiome and its association with the control of pathogens in broiler chicken production: A review. Poultry science, 97(3), 1006–1021.
  15. Lin R, Zhi C, Su Y, et al. Effect of Echinacea on gut microbiota of immunosuppressed ducks. Front Microbiol. 2023;13:1091116
  16. Wicaksono WA, Jones EE, Monk J, Ridgway HJ. The Bacterial Signature of Leptospermum scoparium (Mānuka) Reveals Core and Accessory Communities with Bioactive Properties. PLoS One. 2016;11(9):e0163717.
  17. Fukui H. Increased Intestinal Permeability and Decreased Barrier Function: Does It Really Influence the Risk of Inflammation?. Inflamm Intest Dis. 2016;1(3):135-145.
  18. Wu X, Chen H, Gao X, Gao H, He Q, Li G, Yao J, Liu Z. Natural Herbal Remedy Wumei Decoction Ameliorates Intestinal Mucosal Inflammation by Inhibiting Th1/Th17 Cell Differentiation and Maintaining Microbial Homeostasis. Inflamm Bowel Dis. 2022 Jul 1;28(7):1061-1071.
  19. Aldars-García L, Chaparro M, Gisbert JP. Systematic Review: The Gut Microbiome and Its Potential Clinical Application in Inflammatory Bowel Disease. Microorganisms. 2021;9(5):977.
  20. Rasmussen, P.L., Kawakawa: a monograph. Phytonews, published by Phytomed Medicinal Herbs Ltd, 7, 1-7, Sept 2000. ISSN 1175-0251
  21. Rasmussen, P.L., Kawakawa: a promising New Zealand native plant. Pharmacy Today, August 2021. ISSN 1170-1927
  22. Lee W, Ku SK, Min BW, et al. Vascular barrier protective effects of pellitorine in LPS-induced inflammation in vitro and in vivo. Fitoterapia. 2014;92:177-187.
  23. Obst K, Lieder B, Reichelt KV, et al. Sensory active piperine analogues from Macropiper excelsum and their effects on intestinal nutrient uptake in Caco-2 cells. Phytochemistry. 2017;135:181-190.
  24. Arun M, Asha VV. Gastroprotective effect of Dodonaea viscosa on various experimental ulcer models. J Ethnopharmacol. 2008;118(3):460-465.
  25. Rasmussen PL, NZ Native Plants: Part 2. Webinar, by Phytomed Medicinal Herbs Ltd, October 2018.
  26. Zhang D, Liu J, Cheng H, et al. Interactions between polysaccharides and gut microbiota: A metabolomic and microbial review. Food Res Int. 2022;160:111653.
  27. Jalanka J, Major G, Murray K, et al. The Effect of Psyllium Husk on Intestinal Microbiota in Constipated Patients and Healthy Controls. Int J Mol Sci. 2019;20(2):433.
  28. Xu H, Wang S, Jiang Y, et al. Poria cocos Polysaccharide Ameliorated Antibiotic-Associated Diarrhea in Mice via Regulating the Homeostasis of the Gut Microbiota and Intestinal Mucosal Barrier. Int J Mol Sci. 2023;24(2):1423. 
  29. Xiong X, Cheng Z, Wu F, et al. Berberine in the treatment of ulcerative colitis: A possible pathway through Tuft cells. Biomed Pharmacother. 2021;134:111129.
  30. Zhao, A., Jeffery, E. H., & Miller, M. J. (2022). Is Bitterness Only a Taste? The Expanding Area of Health Benefits of Brassica Vegetables and Potential for Bitter Taste Receptors to Support Health Benefits. Nutrients, 14(7), 1434
  31. Ye JH, Fang QT, Zeng L, et al. A comprehensive review of matcha: production, food application, potential health benefits, and gastrointestinal fate of main phenolics [published online ahead of print, 2023 Apr 3]. Crit Rev Food Sci Nutr. 2023;1-22.

Mānuka and Myrtle Rust

On By HerbBlurbIn Antifungal, Biosecurity, Environment, Herbal Medicine, Manuka, Myrtle Rust, Organic Medicine, Pathogen, Plant MedicineLeave a comment

Last week I attended a two day workshop organised by scientists at Plant and Food Research Ltd and Massey University in Palmerston North, to discuss a range of recent scientific and biosecurity developments, concerning Mānuka (Leptospermum scoparium), an important plant in New Zealand’s natural environment and economy. As with the two day Hui on ‘Mānuka and More’ in Ruatoria and Te Araroa in November last year, this was an excellent event in which more than 30 scientists working actively on Mānuka research presented on a diverse range of subjects and discussed where there could be gaps in our knowledge or research needs for this plant. While Mānuka Honey and essential oil are currently the main two medicinal products produced from Mānuka, numerous other therapeutic applications and potential contributions to preserving our environment, are found within this plant.

Jacqui Horswell and colleagues from the Institute of Environmental Science and Research, have shown that Mānuka and other myrtaceaeous plants seem to be capable of killing the faecal bacterial pathogen Enterobacter coli (E. coli), by enhancing the die-off of this and other pathogenic organisms that pass through their root systems. A field trial involving riparian planting of Mānuka is just getting going, to see whether laboratory results extend to helping to reduce animal effluent flows into a polluted lake. A lake which was once pristine and a treasured swimming area, but in recent years has changed into a green and dirty waterway due largely to dairy industry runoff, has been selected for this trial.

Hayley Ridgway from Lincoln University presented some interesting findings concerning novel and potentially useful mycorrhizae (fungi) and endophytic bacteria associated with the roots of Mānuka, some of which I wrote about in my previous blog. Inoculation of Mānuka plants with different mycorrhizae causes significant alterations in their growth rates and essential oil composition, highlighting the complex inter-relationships between microbes associated with Mānuka, and its production of phytochemicals including some with bioactive properties.

Other presentations were made on experiences to date involving plantations of Mānuka which have been established at a number of North Island sites in recent years. Challenges include site access, weeds, pests, and the relative attractiveness of different genetic lines to bees. A comment made by one of the presenters that while humans have had multiple generations of experience with cultivation and enhancing performance characteristics of crops such as wheat and rice, our experience with Mānuka plantations spans less than 10-15 years to date.

The hottest topic at the workshop, however, was the recent finding of isolated outbreaks of Myrtle Rust (Austropuccinia psidii) in New Zealand nursery and garden grown specimens of Mānuka and the native tree, Ramarama (Lophomyrtus bullata). This pathogenic fungi originated from Brazil where it causes guava rust, but spread internationally into North America in the 1880’s, and was first reported in Australia in 2010.  Australia is home to around half of the world’s Myrtaceae (Myrtle family) plant species, including Eucalyptus (850 species), Melaleuca (176 species) and Callistemon species.

Outbreak of Myrtle rust has had a devastating effect on much of the east coast as well as other areas of Australia, where it has resulted in ecosystem collapse for certain plant species. To date it has only been found in isolated locations in Northland, Waikato, Bay of Plenty and Taranaki, although it is widespread on Raoul Island in the Kermadec group, about 1,100km to the north-east of New Zealand.

Myrtle rust spores can easily spread across large distances by wind, or via insects, birds, people, or machinery, and it is thought the fungus arrived in New Zealand carried by strong winds and significant weather events from Australia.

The Myrtle Rust Strategic Science Advisory Group is working hard to assess and try to ameliorate the widespread environmental, economic, social and cultural impacts this plant pathogen could have on New Zealand. Apart from Mānuka and Ramarama, other indigenous Myrtaceae species such as Pohutakawa (Metrosideros spp) and Swamp Maire (Syzygium maire), are under risk. Priorities including acceleration of scientific research into the biology of the pandemic strain detected here, pathways of spread, surveillance, management, exploring plant susceptibility and resistance, and coordinating and communicating a management plan that has widespread engagement by communities, scientists, industry and Maori stakeholders and landowners, councils and government.

The Ministry for Primary Industries (MPI) and the Department of Conservation (DOC), with the help of local iwi, the nursery industry, and local authorities are running an operation to determine the scale of the situation and to try and contain and control myrtle rust in the areas it has been found. However, emergence of the infection and appearance of the distinctive yellow or brown leaf discolouration may not become fully apparent until the spring, and a better assessment of the number of infection sites and their extent, may not be possible until then.

The arrival of Myrtle Rust in New Zealand means that the task of collecting and storing seed of New Zealand indigenous Myrtaceae including Mānuka, has now become urgent. The NZ Indigenous Flora Seed Bank (NZIFSB), a collaborative project between Massey University, AgResearch, Landcare and the Department of Conservation, with support from the NZ Plant Conservation Network and the Millennium Seedbank at Kew in the UK, was established in 2013. NZFISB has been doing some really valuable work to collect and store seeds aimed at preserving a wide range of biodiversity within New Zealand native plant species. More than 130 volunteer seed collectors have been trained to date, and plans are underway to extend this and the level of community participation, to try to better protect our native plants for generations to come.

Refs:

http://www.nzpcn.org.nz/page.aspx?conservation_seedbank

http://www.mpi.govt.nz/protection-and-response/responding/alerts/myrtle-rust/