Ligustrum lucidum – noxious weed or useful osteoporosis treatment?

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It’s a Saturday in early February in NZ, and the warm summer days linger on. Trying to retain some of the holiday vibe, we pack a picnic and togs and head out with some friends to Cornwallis Beach, on Auckland’s west coast.

On the way, as we drive up through Glen Eden and Titirangi, I find it difficult not to comment on the frequent appearance of Glossy Privet (Ligustrum lucidum) trees, on road and garden verges including an alarming number of indentations into adjacent native bush. Prominent this time of year with their creamy-yellow flower clusters amidst a dark green foliage background, they remind me of the Elder trees whose flowers used to similarly draw my attention every summer when I lived in the UK.

Unlike Elder in the UK, however, Glossy Privet is not native to New Zealand, and just like hundreds of other clever plant species, has become so well colonised here it is classed as a ‘noxious’ plant. It is, in fact, according to the NZ Plant Conservation Network(1), New Zealand’s most invasive introduced tree, as the dark purple brown berries make a tasty treat for our large bird population who then excrete the seeds far and wide. Not only around Auckland, but on a drive back from Gisborne to Auckland in January, I again couldn’t help but notice the large number of these trees in numerous locations throughout the 500km journey.

While my frequent comments concerning this tree to family or other fellow passengers over the past couple of years may seem obsessive, my fascination with it stems from the fact that it is also highly medicinal. In its native China, the small fruits of Glossy Privet (Nu-Zhen-Zi) are commonly used to strengthen bones, and it is an ingredient of many herbal formulae for the treatment of osteoporosis.  Osteoporosis is a condition characterised by low bone mass and micro-architectural deterioration of bone tissues leading to increased bone fragility. It is the leading cause of bone fractures in older adults, and is increasing in prevalence in both women and men, as populations age(2).

Several scientific papers have appeared in recent years supporting Glossy Privet’s beneficial effects in osteoporosis. These include increased circulation levels of vitamin D (1,25-dihydroxyvitamin D3) and improved calcium balance in mature female rats(3,4). Higher bone mineral density and positive effects on bone microstructure, have also been reported following its administration to young male and female growing rats(5-7). As optimising peak bone mass during early life is a key preventive action against osteoporosis, these findings collectively suggest that regular intake of Glossy Privet may well have a preventive effect against this debilitating condition in humans.

In Asian traditional medicine Glossy Privet is also used to treat menopausal problems, blurred vision, tinnitus, rheumatic pains, palpitations, backache and insomnia(8). Other traditional applications supported by recent scientific studies include protection against liver toxins(9, 10), and inhibition of the Hepatitis C (HCV) virus(11).

In China, as with other medicinal herbs, Glossy Privet fruits are sometimes used as an adjunct in cancer therapy (12). Researchers have reported enhanced sensitivity of human colorectal carcinoma cells to the chemotherapy drug doxorubicin(13). Inhibition of the mutagenic activities of benzo(a)pyrene(14) and aflatoxin B1(12) suggest cancer chemopreventive properties, and laboratory studies implicate potential applications in the treatment of human hepatocellular(15) and brain(16) cancer. Animal studies also suggest a possible therapeutic role in diabetes, including protective effects against diabetes-related reproductive deficits(9, 17, 18), and high fat diet-induced obesity(19).

There is clearly potential merit in further evaluating potential therapeutic applications of the fruits of this tree, now found throughout New Zealand and endemic in many other countries. Research to date strongly suggests a significant opportunity for medical herbalists and other clinicians, researchers, health funding providers and conservation agencies, to collaborate to further investigate such medicinal applications. Harvesting its berries and processing these into a prophylactic as well as treatment for osteoporosis alone, would reduce its spread and help protect New Zealand’s precious environment with less use of chemical control measures. This would at the same time also help to reduce Pharmac’s spending on biphosphonates and other osteoporosis treatments, thus potentially enabling more funding towards expensive new generation cancer drugs.

Refs:

  1. New Zealand Plant Conservation Network, www.nzpcn.org.nz
  2. Cawthon PM et al, Ther Adv Musculoskelet Dis 2016; 8(1):15-27
  3. Zhang YZ et al, J Econ Entomol. 2008;101(4):1146-51.
  4. Dong Xl et al, Menopause. 2010;17(6):1174-81.
  5. Feng X et al, Calcif Tissue Int. 2014; 94(4):433-41.
  6. Lyu Y et al, J Bone Miner Metab 2014; 32(6):616-626.
  7. Rasmussen PL, Phytonews 40, ISSN 1175-0251, Phytomed Medicinal Herbs Ltd, November 2014.
  8. Gao L et al, Nat Prod Res 2015; 29(6):493-510.
  9. Yim TK et al, Phytother Res 2001; 15(7):589-592.
  10. Gao D et al, Phytother Res 2009; 23(9):1257-1262.
  11. Kong L et al, Antiviral Res 2013; 98(1):44-53.
  12. Wong BY et al, Mutat Res 1992; 279(3):209-216.
  13. Zhang JF et al, Integr Cancer Ther 2011; 10(1):85-91.
  14. Niikawa M et al, Mutat Res 1993; 319(1):1-9.
  15. Hu B et al, Oncol Rep 2014; 32(3):1037-1042.
  16. Jeong JC et al, Phytother Res 2011; 25(3):429-434.
  17. Feng SL et al, Asian J Androl 2001; 3(1):71-73
  18. Zhang Y et al, J Ethnopharmacol 2014; 158, PtA:239-245.
  19. Liu Q et al, Nat Prod Commun 2014; 9(10):1399-1401
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