Global panic has set in from the December 2019 outbreak of a new human form of coronavirus (SARS-CoV-2), responsible for causing the disease COVID-19 initially in China, and which has now become a pandemic as it spreads in multiple countries.

This virus is genetically closely related to the SARS-CoV-1 virus which first appeared in 2003, and is different to seasonal influenza. The mortality rate of COVID-19 is approximately 36 per 1,000 people, with highest rates in the elderly and those with pre-existing respiratory or cardiovascular disease, or diabetes. By comparison, the death rate from seasonal influenza is approximately 1 per 1,000 people (European Centre for Disease Prevention and Control (1).

As at the time of writing, at least 218,000 cases of COVID-19 and more than 8000 deaths have been reported globally, and numbers are increasing rapidly. No vaccine or proven drug treatment options are available, and panic buying in many countries has led to supermarket shelves been cleared of items such as toilet paper and hand sanitiser. Natural health products aimed at enhancing immunity, are also in high demand and supply shortages are becoming apparent.

It is therefore appropriate to start thinking about the various common herbs and spices, weeds and other plants available in our individual communities, that may be useful to support the need for greater ‘self care’ in the next few weeks or months.

This article will discuss some culinary herb and spice options, and will be followed by others on weeds and native plants, growing here in Aotearoa, New Zealand.

 

Part 1: Culinary spices and herbs:

Many well-known spices and herbs used in cooking have useful antimicrobial properties, and it is these in addition to their effects on the human palate, that made them very important and highly valued in early human trade. These include oregano, thyme, rosemary, ginger, garlic, onions, welsh onions, black mustard, cinnamon and blackseed.

While for the majority it is their antibacterial rather than antiviral actions that are most established, several seem to have effects that could be directly relevant to the prophylaxis or management of a COVID-19 infection.

While the COVID-19 situation is evolving rapidly and there is much not well understood, a large percentage of those who became severely ill or died from previous viral pandemics in 1918, 1957, 1968 and 2009, developed bacterial pneumonia, with Staph aureus and Strep pneumoniae being the most common bacterial pathogens (2). Evidence to date suggests that this virus is likely to be similar, and a significant proportion of SARS-1 and at least 10% of COVID-19 patients, develop such secondary bacterial infections in addition to infection with the virus itself (3).

These bacterial co-infections are associated with significant inflammation, and sometimes pneumonia and death. Pandemic viral infections make their development more likely, as viruses express bacterial adhesion receptors and can invoke an inflammatory response that can disturb the integrity of the respiratory tract’s normal physical barrier to bacteria (4). Recent studies in children also reveal complex interactions between viruses, the respiratory microbiome and the host’s immune response, which may have an impact on the pathogenesis and severity of respiratory virus infections (5).

While appropriate antibiotics can be life-saving and if available should be prescribed during serious bacterial lung infections and pneumonia, antibiotic resistance due to their overuse, and limited access to antibiotics for many, are seriously growing concerns for the human race. Therefore, herbs and spices that have traditional and/or scientific evidence of strong antibacterial activities, may be useful and should be considered. This is particularly likely to be the case, where their traditional use relates to conditions affecting the lungs or respiratory tract.

Some such culinary herbs and spices that spring to mind, are Garlic, Horseradish, Thyme and Oregano. These or other herbs traditionally used for congestion or infection of the lungs, may provide relief to some patients, and help lessen the risk of secondary bacterial infections and need for antibiotics or other drug-based medications.

 

Ginger (Zingiber officinale)

This is one of my favourites, for so many reasons. Much more than just a warming spice to add a bite to our food and smoothies, the rhizome and root of ginger has pronounced anti-inflammatory (6) and possibly some antiviral (7,8) properties, which may be useful.

High concentrations of a water extract of fresh but not dried ginger showed anti-viral activity against human respiratory syncytial virus in human respiratory tract cell lines, this activity being greatest when given before viral inoculation (9). A similar dose-related antiviral activity was measured in vitro against the avian influenza virus H9N2 (10).

Inhibition of Hepatitis C viral protease has been reported for both aqueous and methanol extracts of ginger (11). An Eqyptian clinical study found administration of a hydroethanolic extract to Hepatitis C patients decreased their viral load and improved liver function. These effects were enhanced when ginger was combined with blackseed (Nigella sativa) (12).

Zingiber montanum (Cassumuna ginger), a related Asian ginger species which is noxious in various countries, has been reported to more than halve the level of infectivity of the highly pathogenic avian influenza virus H5N1 in a cell-based assay (13).

Apart from potential antiviral effects, studies on animals suggest that modulation of the immune response to viral infections, may contribute to ginger’s beneficial effects (14, 15). One study for example, measured no inhibitory effect on the growth of influenza A virus for ginger root extract itself, but found it to produce activation of the macrophages leading to production of TNF-alpha (16).

While like other culinary herbs and spices specific anti-COVID-19 activity is unproven, there seems to be much to gain from preparing a hot drink by gently simmering a good few slices of the rhizome of this popular spice in a saucepan with the lid on it, then drinking this as a decoction. Particularly when stuck at home during an enforced winter lockdown!

 

Garlic (Allium sativum)

The reputation of garlic bulbs as an antimicrobial agent is strong, but this pertains mainly to antibacterial and antifungal activities, and the evidence it helps with viral infections such as colds and influenza, is mixed (17, 18).

One clinical trial in healthy volunteers found 90 days administration of an aged garlic extract to reduce the severity and symptoms, but not the frequency of colds and influenza (19).

Promising findings have however, been recently reported for a gold nanoparticle product made from garlic extract, as a potent inhibitor of the measles virus (20).

Like garlic, other Allium species such as onions, leek, shallot, scallion, and chives also show evidence of useful antimicrobial properties, and contain a plethora of bioactive compounds such as organosulfur compounds, polyphenols, saponins, fructans, and fructo-oligosaccharides (21). Green tops of Welsh onions (Allium fistulosum) for example, contain a fructan which showed inhibitory effects on replication of influenza A and enhanced antibody production against this virus in mice (22).

Garlic extracts show activity against Streptococcus pneumoniae and Klebsiella pneumoniae (23). Garlic’s antimicrobial activities are largely due to sulphurous compounds such as allicin (diallylthiosulfinate), a volatile compound produced when garlic is crushed. German researchers have shown allicin vapour to inhibit the growth of a range of lung pathogenic bacteria, including multi-drug resistant strains (24).

This suggests that frequent direct inhalation of crushed garlic may be useful to help combat bacterial lung infections, and could be a useful adjunct with oral antibiotics, where bacterial co-infection exists or is suspected.

 

Holy Basil (Tulsi) (Ocimum tenuiflorum, O sanctum) and Sweet Basil (Ocimum basilicum)

A popular aromatic herb used in cooking particularly by the Indian community, the leaves of Holy Basil or Ocimum tenuiflorum as well as other Ocimum species including the related so-called European or sweet Basil (Ocimum basilicum), are revered for their medicinal properties. Both these and other Ocimum species (but particularly Holy Basil) also contain the triterpenoid compound ursolic acid, which exhibits strong antiviral activity against a range of viruses such as herpes simplex, adenoviruses, rotavirus, coxsackievirus and enterovirus (25, 26).

A crude extract and terpenoid isolated from Holy Basil leaves has shown promising antiviral properties against H9N2 virus (27). In vitro activity against the HIV virus, has also been reported for the related Ocimum gratissimum (28).

Recent studies have also found an extract of sweet basil leaves to inhibit attachment and entry of the Zika virus into the host cell (29). Evidence of possible neuraminidase inhibitory activity against the H1N1 swine flu virus for the flavonoid compound apigenin, extracted from Holy Basil and found in a range of other medicinal plants, has also been reported (30).

While becoming out of season now in New Zealand, for those in warmer climates or with greenhouse growing options, planting lots of these two easy to grow herbs now, may pay dividends beyond their yummy flavours in the future.

 

Blackseed (Nigella sativa) or Ketza (black cumin)

This is a highly regarded traditional remedy used by many Asian, Middle Eastern and northern Africa ethnic groups in cooking and for a wide range of health issues, including to enhance immunity and to treat diarrhoea and various types of infections (31).

Protection against murine cytomegalovirus has been reported for blackseed oil (32). Eqyptian studies found blackseed administration to significantly reduce the viral load in patients with Hepatitis C (33), and to inhibit replication of this notoriously resilient virus (34). Six weeks administration of a combination of blackseed with echinacea also enhanced the immune response after vaccination against the H9N2 avian influenza virus, and reduced the pathogenicity of infection in stressed chickens (35).

 

Cinnamon (Cinnamonum zeylanicum)

The bark from various Cinnamonum species found in Sri Lanka, Indonesia and now cultivated in other Asian countries, has been traded for more than 2000 years, and was imported by Arabs to Eqypt, Venice and Europe, where it was used to preserve meats as well as for flavour. Control of the Cinnamon trade was a key factor in Portuguese (then Dutch) control of Sri Lanka, in the 16^th century.

Potential benefits in fever management have been reported using an influenza virus infection model in mice (36), and antiviral effects against H1N1 Influenza A and herpes simplex viruses, as well as antibacterial effects against Staph aureus and Strep pneumoniae, shown for a blend of Cinnamomum zeylanicum, Daucus carota (wild carrot), Eucalyptus globulus (eucalyptus) and Rosmarinus officinale (rosemary) essential oils (37). A nanoparticular form of Cinnamomum cassia also exhibited promising activity against the H7N3 Influenza A virus (38). Trans-cinnamaldehyde, a major constituent of cinnamon essential oil exhibits in vitro antiviral activity against influenza A/PR 8 virus, and when given by nasal inhalation increased the survival rates of mice infected with a respiratory virus (39).

Cinnamon, its essential oil and its key constituents cinnamaldehyde and cinnamic acid also possesses strong antibacterial activity against a range of pathogenic bacteria (40), so incorporating some of this spice into your winter wellness warming beverage or mulled wine could be a good move.

 

Horseradish (Armoracia rusticana)

Not just a sought after culinary sauce, the roots of this strong and distinctive plant, have a long tradition of use particularly in Europe, for the treatment of bronchial infections.

Isothiocyanates from horseradish root exhibit broad spectrum antibacterial activity in vitro (41), and a mixture of horseradish when mixed with Nasturtium (Tropaelum majus), showed good activity particularly against Haemophilis influenzae, and intermediate activity against Staph aureus, Strep pneumoniae, Klebsiella pneumoniae and Strep pyogenes (42). Some evidence of prophylaxis against the H3N2 influenza virus has been reported in animal studies (43), though as with many of the herbs and spices I have mentioned, large doses are likely to be required.

While not widely grown here in New Zealand, it isn’t difficult to cultivate, and in fact can become ‘weedy’, not unlike how it grows in many locations in the U.K.

Other spices that may be useful, include Turmeric (Curcuma longa), and Black mustard (Brassica juncea). Both water and ethanolic extracts of black mustard have been reported by Korean researchers to exhibit in vitro activity against influenza virus A/H1N1 (44,45). Researchers in Thailand recently screened some Asian medicinal plant extracts and found ethanolic extracts of turmeric root as well as the leaf of guava (Psidium guajava), to have good in vitro activity against the H5N1 influenza virus (46).

While COVID-19 is a highly virulent and very challenging virus to combat and at the current time we have no research establishing the clinical efficacy of any of the herbs and spices I have mentioned, there is an urgent need to take an interest in this subject and what dietary interventions may perhaps assist, with infection prophylaxis at least. Similarly there are a number of weeds and native plants growing in our beautiful country that may also be helpful, and which I will discuss in subsequent postings.

I’m not lucky enough to be living in a bush area where the large, soft-leafed NZ native plant Rangiora (Brachyglottis repandra, “Bushman’s Friend”) is endemic and so if we run out of toilet paper will need to invoke other methods, but I’m feeling OK about having everyday plants on hand to take as teas or inhalations, should I or my family need to in the coming months.

 

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