Anti-inflammatory Compounds from the Olive Tree’s Cousin, the Common Privet

A research team, led by sensory scientists at the Monell Chemical Senses Center, reported in the International Journal of Molecular Sciences⁽¹⁾ that privet leaves yield significant amounts of both oleocanthal and its closely related compound oleacein. The insight that oleocanthal is a powerful anti-inflammatory compound came from an earlier observations⁽²⁾ by Monell scientists that the sensory property of high-end extra virgin olive oils - a characteristic tickle or burn in the throat - resembled the same sensory property of a common anti-inflammatory drug, ibuprofen.

Further research⁽³⁾ at Monell showed that this burn was caused primarily by oleocanthal and that the characteristic sensation was due to the activation of the ion channel TRPA1 associated with the trigeminal nerve.

“These compounds are thought to account for many of the health-related benefits of extra virgin olive oils, and more broadly, the Mediterranean diet” said first author Catherine Peyrot des Gachons, PhD, Monell Senior Research Associate, explaining the keen interest in the health properties of compounds found in olive oil.

Since the first Monell findings on oleocanthal, many subsequent studies from outside Monell have pointed to these compounds having the potential for treating cancer, Alzheimer’s disease, and other inflammation-related diseases. However, virtually all of these studies have been in cell-based assay systems or animal models.

Proving these compounds enhance human health requires rigorous human clinical trials. Lack of access and financial factors have discouraged many organizations from investing in such trials. Oleocanthal and oleacein are very difficult to synthesize, therefore the sources of gram-scale amounts of these compounds, which are necessary for extensive testing at the scale of human clinical trials, has required the use of commercially valuable extra virgin olive oil, since olive leaves contain little or no oleocanthal. 

The Monell team sought an alternative source. Enter the privet (Ligustrum vulgare), a common fast growing, semi-evergreen shrub in the olive family, which could provide a low-cost and more geographically ubiquitous source of these valuable compounds.

The team’s investigations confirmed the presence, previously reported by others, of oleocanthal and oleacein in the leaves of the common privet and demonstrated that appropriately treated extracts can serve as a rich alternative source of both compounds. 

The Monell team’s efforts advanced these ideas and discovered that there are substantial differences among privet species in the concentration of oleocanthal and oleacein in their leaves. In addition, seasonal leaf-collection time and the leaf-developmental stage were less influential in any differences contributing to these concentrations. 

“This new study is part of the continuing story of Monell’s focus on a deeper understanding of the pharmacology of oleocanthal, with the ultimate goal of enhancing human health,” said Peyrot des Gachons.

Reference:

1. https://www.mdpi.com/1422-0067/25/22/12020

2. https://pubmed.ncbi.nlm.nih.gov/16136122/

3. https://pubmed.ncbi.nlm.nih.gov/21248124/

(Newswise/LT)