Anti-alpha-glucosidase Alkaloids from the Root Bark of Zanthoxylum rhetsa

Abstract

The hexane and ethyl acetate extracts from the root bark of Zanthoxylum rhetsa were investigated. Eight known alkaloids, ??dihydroavicine (1), dihydronitidine (2), paraensidimerine C (3), N-methylflindersine(4), 8-acetonyldihydroavicine (5), paraensidimerine A (6), 8-acetonyldihydronitidine (7), and skimmianine (8) were isolated. Among them, alkaloids 3-6 were obtained for the first time from this plant. Compound 5 exhibited the highest a-glucosidase inhibitory activity against maltase and sucrase with IC₅₀ values of 1.72 and 0.45 mM, respectively. Subsequent investigation on mechanism underlying inhibitory effect of 5 indicated that it blocked maltase and sucrase function by mixed inhibition through competitive and noncompetitive manners. The SAR information obtained from the series of benzophenanthridine alkaloids showed that the presence of the methylenedioxy moiety on C-2 and C-3 and acetonyl group of compound 5 are essential for a-glucosidase inhibitory activity.