The methanol extract from the bark of Shorea roxburghii (Dipterocarpaceae, "Phayom" in Thai) was found to suppress plasma triglyceride elevation in olive oil-treated mice, and also to inhibit pancreatic lipase activity (IC(50) = 31.6 μg/ml). From the extract, two new 3-acetyl-4-phenyl-3,4-dihydroisocoumarins, phayomphenols A(1) (1) and A(2) (2) were isolated, together with 22 known compounds. The structures of 1 and 2 were elucidated on the basis of chemical and spectroscopic evidence, including X-ray crystallographic analysis. Among the isolates, several oligostilbenoids, including (-)-hopeaphenol (3) and (+)-isohopeaphenol (4), showed inhibitory effects on plasma triglyceride elevation at a dose of 200 mg/kg p.o. and pancreatic lipase inhibitory activity (IC(50) = 32.9 and 26.5 μM, respectively).