Gakolanone: a new benzophenone derivative from Heckel stem-bark.

Gakolanone (3',5'-digeranyl-2',4',6',3-tetrahydroxybenzophenone; ), a novel benzophenone derivative was isolated from the hexane extract of Heckel stem-bark along with three known 3-8'' linked biflavonoids: 3'',4',4''',5,5'',7,7''-heptahydroxy-3,8''-biflavanone (); 3'',4',5,5'',5''',7,7''-heptahydroxy-4-methoxy-3,8''-biflavanone () and 4',4''',5,5'',7,7''-hexahydroxy-3,8''-biflavanone () from the ethanol extract. The compounds were characterized primarily using 1 D and 2 D nuclear magnetic resonance spectroscopy and mass spectrometry and by comparing with literature. The compounds were subjected to alpha-amylase enzyme inhibitory assay using DNSA (3,5-dinitrosalicylic acid) reagent with acarbose used as the standard drug. All the compounds were found to show alpha-amylase inhibitory activities with IC of 21.4 ± 1.5, 9.9 ± 0.2, 15.3 ± 2.3, 12.9 ± 2.3 µg/mL respectively. All the compounds exhibited better alpha-amylase inhibitory activities than the standard drug, acarbose (IC= 38.1 ± 8.3 µg/mL).