Searching for iridoids from tropical plants: detection, isolation and antibacterial activity
Iridoid glycosides, which form an important group of cyclopentane monoterpenoids, are biosynthesized by a large number of plant species belonging to approximately twenty important botanical families. Although they possess a wide range of pharmacological and biological properties, such as anti-allergic, anti-inflammatory, antibacterial, antifungal, antiviral, anti-oxidative, immunomodulatory, neuroprotective, etc. [1,2], no molecule is currently used as a drug. However, iridoids, which possess a highly functionalized aglycon, may be regarded as starting material for the synthesis of a number of new chiral molecules.
In this context, we have launched a research project aimed at searching for new chiral scaffold of iridoid-type from higher plants of the tropical biodiversity. This project, part of an ANR program called IRNA-CHIR, focuses on species, which contain high iridoids content. For this study, approximately 500 species were selected from iridoid-containing families, and were subjected to a methanolic extraction followed by dichloromethane recovery. Then a methodology, based on the combination of different analytical and spectroscopic techniques such as TLC, LC/UV/DEDL, LC/MS and NMR, was developed in order to select the plants of interest. Parallel to this study, we conducted an evaluation of the antimicrobial potential of extracts and isolated compounds.
Our initial results show that no new iridoid was discovered to date, despite the fact that the species selected have never been studied, and few containing-iridoid extracts exhibit potent antibacterial activity.
We will present and discuss the methodology used to detect and isolate iridoids, and the antibacterial activity of the extracts selected and pure compounds.
Acknowledgement: This 4-years project is funded by the French National Research Agency. We are gratefull to our foreign partners: Dr K. Awang (University Malaya, Malaysia), Dr. P. Rasoanaivo (IMRA, Malagasy), Dr. V.H. Nguyen (VAST, Vietnam), Dr. B. Kiremire (University of Makerere, Uganda) enabling us, through official agreements between CNRS and various public institutions, to have access to a rich biodiversity.
References: 1. Dinda B et al. (2007) Chem Pharm Bull 55(5): 689–728 2. Dinda B et al. (2009) Chem Pharm Bull 57(8): 765–796