<jats:title>Abstract</jats:title><jats:p>Five new β‐carboline alkaloids, 6,12‐dimethoxy‐3‐(2‐hydroxylethyl)‐β‐carboline (1), 3,10‐dihydroxy‐β‐carboline (2), 6,12‐dimethoxy‐3‐(1‐hydroxylethyl)‐β‐carboline (3), 6,12‐dimethoxy‐3‐(1,2‐dihydroxylethyl)‐β‐carboline (4), and 6‐methoxy‐3‐(2‐hydroxyl‐1‐ethoxylethyl)‐β‐carboline (5), and two new natural products, 6‐methoxy‐12‐hydroxy‐3‐methoxycarbonyl‐β‐carboline (6) and 3‐hydroxy‐β‐carboline (7) were isolated from the stems of <jats:italic>Picrasma quassioides</jats:italic> along with 16 known β‐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. Copyright © 2010 John Wiley & Sons, Ltd.