Beta-carboline alkaloids from the stems of Picrasma quassioides.

Five new beta-carboline alkaloids, 6,12-dimethoxy-3-(2-hydroxylethyl)-beta-carboline (1), 3,10-dihydroxy-beta-carboline (2), 6,12-dimethoxy-3-(1-hydroxylethyl)-beta-carboline (3), 6,12-dimethoxy-3-(1,2-dihydroxylethyl)-beta-carboline (4), and 6-methoxy-3-(2-hydroxyl-1-ethoxylethyl)-beta-carboline (5), and two new natural products, 6-methoxy-12-hydroxy-3-methoxycarbonyl-beta-carboline (6) and 3-hydroxy-beta-carboline (7) were isolated from the stems of Picrasma quassioides along with 16 known beta-carboline alkaloids (8-23). The structures of new compounds were determined by extensive spectroscopic analyses, and the 1D and 2D NMR data of compounds 6, 7 and 10 were reported for the first time. The bioassays showed that only compounds 14 and 16 could enhance the differentiation of 3T3-L1 preadiocytes accompanied by secretion of adiponectin proteins among these 23 compounds.