A new mexicanolide−type limonoid from the bark of Swietenia microphylla

Abstract

Limonoids are a class of highly oxygenated natural compounds biosynthesized from a precursor with a 4,4,8-trimethyl-17-furanylsteroid skeleton via complicated oxidation and rearrangement reactions. These compounds are mainly found in the families Meliaceae, Rutaceae and present as the major natural products in species of the genus Swietenia. They are well known for their structural diversity, which is classified into different types including mexicanolide, phragmalin, azadirone, evodulin, gedunin, and andirobin. They have shown highly potent effects with an extensive range of biological activities, such as antifeedant, insecticidal, antibacterial, antifungal, hypoglycemic, antimalarial, antioxidant, antiviral, anti-inflammatory, and cytotoxic. This paper presents the results of an investigation of the chemical constituents of an ethyl acetate extract from the bark of Swietenia microphylla and studies the biological activities of the isolated compound. Repeated column chromatography on silica gel with different eluents isolated a pure compound. Analysis of UV−Vis, HRESIMS and 1D, 2D-NMR spectra led to the structural elucidation of a new mexicanolide−type limonoid, named 11α-hydroxy-2,3-di-O-acetylanthothecanolide. The compound was tested in vitro for α-glucosidase inhibitory activity and cytotoxic effects against four human cancer cell lines (KB carcinoma, A549 lung cancer, HepG2 hepatoma, MCF-7 breast cancer cells), and displayed almost no activity.