Biomimetic transformation and biological activities of globiferin, a terpenoid benzoquinone from Cordia globifera

Abstract

A new 10-membered ring meroterpene (1), named globiferin, was isolated from root extracts of Cordia globifera. Biomimetic transformations of 1 and its derivatives, either by acid cyclization or by Cope rearrangement, provided information relating to the biogenesis of cordiachromes A-C. Globiferin (1) underwent Cope rearrangement upon refluxing in xylene and DMSO-d6 to yield cordiachrome C (3) and cordiaquinol C (4), respectively. Heating in DMSO-d6 resulted in an unexpected reduction of a quinone moiety. Globiferin diacetate (1b) cyclized under acidic conditions to give compounds 10 and 11, respective derivatives of natural cordiachromes B (2) and A (12). The present study indicates that globiferin (1) is a genuine intermediate for the biosynthesis of cordiachromes in Cordia species. Compounds 1 and 3 exhibited significant antimycobacterial activity, with MIC values of 6.2 and 1.5 μg/mL, respectively. Antimalarial, antifungal, and cytotoxic activities of 1 and its derivatives were also evaluated. © 2009 American Chemical Society and American Society of Pharmacognosy.