Laxative effect of agarwood leaves and its mechanism.

We investigated the laxative activity of an extract of agarwood leaves from Aquilaria sinensis. The laxative activity was measured in mice by counting the stool frequency and stool weight, and the drugs were orally administered. An acetone extract of agarwood leaves and senna (a representative laxative drug) both increased the stool frequency and weight, but a methanol extract did not. The laxative effect of the acetone extract was milder than that of the anthraquinoid laxative, senna, and the former did not induce diarrhea as a severe side effect. We identified the main constituent contributing to the laxative effect of the acetone extract as genkwanin 5-O-beta-primeveroside (compound 4). Compound 4 strengthened the spontaneous motility and induced contraction in the ileum. This ileal contraction induced by compound 4 was inhibited by atropine, but not by azasetron, suggesting that the effect of compound 4 was mediated by acetylcholine receptors, and not by serotonin. The laxative mechanism for compound 4 may in part involve stimulation of intestinal motility via acetylcholine receptors.