Three new α-glucosidase inhibitors from guggul, the oleogum resin of Commiphora wightii.

Three new compounds; epi-mukulin, (Z)-Δ(1,2) dehydroguggulsterone and Δ(6,7)dehydro-20-hydroxygugglsterone were isolated from the n-hexane-soluble fraction (HSF) of the methanol extract of guggul, the oleogum resin of Commiphora wightii together with six known compounds: diasesartemin, (+)-epi-magnolin, (+)-diayangambin, gugglsterol I, (E)-guggulsterone and (Z)-guggulsterone. Their structures were elucidated on the basis of different spectroscopic data. α-Glucosidase inhibitory effects of HSF and the isolated compounds were evaluated calorimetrically. The HSF showed significant α-glucosidase inhibitory effect [IC(50) value of 140 µg mL(-1) (p < 0.05)]. Under the assay conditions, diasesartemin (IC(50) = 60.6 ± 0.01 µM) was found to be more potent than the positive control, acarbose (IC(50) = 92.94 ± 0.01 µM); a known α-glucosidase inhibitor (p < 0.05). The IC(50) values of epi-mukulin and (Z)-guggulsterone were found to be 159.33 and 132.14 µM, respectively. Other compounds showed weak α-glucosidase inhibitory effects, <30% inhibition of the enzyme activity at 0.1 mg mL(-1).