Heteroyohimbinoid type oxindole alkaloids from Mitragyna parvifolia

The leaves of the plant Mitragyna parvifolia have afforded two alkaloids, 16,17-dihydro- 17 beta-hydroxy isomitraphylline (1) and 16, 17-dihydro-17 beta-hydroxy mitraphylline (2), together with two known alkaloids, isomitraphylline (3) and mitraphylline (4). The structures of 1 and 2 were elucidated using 1D and 2D NMR spectral methods, including H-1-(HCOSY)-H-1, DEPT, HSQC, and HMBC. Mitraphylline was the main alkaloid constituent. (c) 2006 Elsevier Ltd. All rights reserved.