Indole alkaloids from the stems of Uncaria homomalla

Abstract

Five indole alkaloids were isolated from the stems of Uncaria homomalla Miq. One of them was identified as a heteroyohimbine namely tetrahydroalstonine and the other four as oxindoles, being isopteropodine, isomitraphylline, mitraphylline and speciophylline. The structures of all isolated alkaloids were determined by extensive spectroscopic studies, including comparison of their UV, IR, MS and NMR spectra with the previously reported data.