Alstoscholarisine L, a novel caged monoterpenoid indole alkaloid with antifungal activity from Alstonia scholaris

Abstract

Alstoscholarisine L is an architecturally complex monoterpenoid indole alkaloid with a unique ring fusion pattern, isolated from the leaves of Alstonia scholaris. The 6/5/5/6/6/6-membered rings contain two lactonic rings and one aminal carbon and possess seven contiguous aligned stereocenters, three of which are quaternary. Its structure was elucidated by extensive spectroscopic data analyses, quantum chemical computations, and single-crystal X-ray diffraction. The unusual highly fused, cage-like skeleton is possibly derived from picrinine. The fascinating compound exhibited potential antifungal activity against Candida albicans, and its activity was roughly comparable to the first line antifungal drug fluconazole and significantly more effective than the plant-derived antibacterial drug berberine.

Keywords: Alstonia scholaris; Antifungal activity; Candida albicans; Indole alkaloid.