The methanolic extract from guggul-gum resin, the resin of Balsamodendron mukul, was found to inhibit nitric oxide production in lipopolysaccharide-activated mouse peritoneal macrophages (IC(50) = 13 microg/mL). From the methanolic extract, three new polypodane-type triterpenes, myrrhanol B and myrrhanones B and A acetate, and a new octanordammarane-type triterpene, epimansumbinol, were isolated together with 17 known compounds including progesterone and the related steroids. The absolute stereostructures of new triterpenes were elucidated on the basis of chemical and physicochemical evidence. The several constituents showed inhibitory effects on nitric oxide production and induction of inducible nitric oxide synthase.