Eleven new metabolites, butanolides 1-6, lignan derivatives 7-9, sesquiterpene 10, and 3',4'-seco-flavane derivative 11, have been isolated from an ethanol extract of Machilus wangchiana. Twenty known compounds, including ginkgolides A and B (16 and 17), were also isolated. Their structures and absolute configurations were determined by spectroscopic and chemical methods. Compounds 7, 8a, 8b, 9, 11, (+)-guaiacin (12), meso-dihydroguaiaretic acid (13), and hamabiwalactone A (15) showed potent in vitro activities against the release of beta-glucuronidase in rat polymorphonuclear leukocytes (PMNs) induced by platelet-activating factor (PAF), with 42.5-75.6% inhibition at 10(-5) M. Compounds 8, 8a, 8b, 9, and 11 reduced dl-galactosamine (GalN)-induced hepatocyte (WB-F344 cells) damage with 39.4 +/- 6.3% to 53.6 +/- 3.5% inhibition at 10(-4) M. Isomahubannolide-23 (14) was cytotoxic against human stomach cancer (BGC-823) and ovarian cancer (A2780) cell lines, with IC(50) values of 0.13 and 2.66 muM, respectively.