In Europe holly is a spiky, festive plant that gets an annual spotlight in wreaths and garlands at Christmas. But taxonomically holly is a genus, Ilex, of 400-600 species. Ilex aquifolium (‘holly’) is the dominant species in the UK and Europe but worldwide the genus includes evergreens, deciduous trees, shrubs and climbing plants.
One holly species, I. asprella, is known locally in its native southern China as Gang-Mei. Tea made from the roots and leaves is a traditional medicine for influenza, bacterial infections and lung abscess. Several studies have shown that extract from I. asprella contains bioactive compounds; this recent systems biology paper profiled the biosynthetic pathway for Ilex triterpinoid saponins. Others have demonstrated that root extract can inhibit flu viruses and sooth inflammation, and this year a team of researchers at the Guangzhou University of Traditional Chinese Medicine showed that I. asprella root extract is also fairly effective at reducing the impact of acute respiratory distress syndrome in mice.
A slow invasion of English holly (the festive kind), I. aquifolium, is causing a bit of a stir in the North West USA. This paper in the rather niche Northwest Science journal sampled holly in a forest in Washington state. The authors looked at spatial distribution and age data to estimate that both vegetative and seed-based spread are increasing exponentially. The paper states that the population doubling time is about 5 years, and individual holly trees grow slowly, so hopefully the situation will be controlled quite easily.
For more varied Christmas plant science, check out my Christmas post from 2012, which features frankincense, mistletoe, fir trees and more holly.
Dai WP, Li G, Li X, Hu QP, Liu JX, Zhang FX, Su ZR, Lai XP. 2014. The roots of Ilex asprella extract lessens acute respiratory distress syndrome in mice induced by influenza virus. Journal of Ethnopharmacology 155 (3): 1575–1582
Zheng X, Xu H, Ma X, Zhan R, Chen W. 2014. Triterpenoid saponin biosynthetic pathway profiling and candidate gene mining of the Ilex asprella root using RNA-Seq. International Journal of Molecular Sciences 15(4): 5970-87
Stokes DL, Church ED, Cronkright DM and Lopez S. 2014. Pictures of an Invasion: English Holly (Ilex aquifolium) in a Semi-Natural Pacific Northwest Forest. Northwest Science 88(2): 75-93.