Antimycobacterial natural products from Heracleum maximum
University of New Brunswick
Tuberculosis is a major global health problem that has limited therapeutic options available. N atural [natural] products have historically p rovided [provided] the majority of anti-infective agents, and represent a promising source of antimycobacterial compounds. The objective of this research was to identify the bioactive constituents of a traditional medicinal plant, Heracleum maximum, through fractionation guided by the microplate resazurin assay (MRA). However, when we tested the methanolic extracts of Heracleum maximum, we found the MRA to be problematic, providing inconsistent results. The conditions of the MRA were optimised to provide a standard screening protocol for use in screening and bioassay-guided fractionation of methanolic plant extracts. The optimised MRA was then used to isolate eight antimycobacterial compounds from the Heracleum maximum extract. Among the isolated compounds the polyacetylene, (3R,8S)-falcarindiol, and the furanocoumarin, 6-isopentenyloxyisobergapten, expressed the greatest inhibitory activities; whereas the remaining furanocoumarins, bergapten, isobergapten, angelicin, sphondin, pimpinellin, and isopimpinellin exhibited only modest activities.