Gakolanone: a new benzophenone derivative from Garcinia kola Heckel stem-bark

Abstract

Gakolanone (3',5'-digeranyl-2',4',6',3-tetrahydroxybenzophenone; 1), a novel benzophenone derivative was isolated from the hexane extract of Garcinia kola Heckel stem-bark along with three known 3-8'' linked biflavonoids: 3'',4',4''',5,5'',7,7''-heptahydroxy-3,8''-biflavanone (2); 3'',4',5,5'',5''',7,7''-heptahydroxy-4-methoxy-3,8''-biflavanone (3) and 4',4''',5,5'',7,7''-hexahydroxy-3,8''-biflavanone (4) 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 in-vitro 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 IC₅₀ 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 (IC₅₀= 38.1 ± 8.3 µg/mL).

Graphical Abstract

Keywords:

• Garcinia kola stem-bark
• gakolanone
• benzophenone
• biflavonoids
• DNSA reagent
• alpha-amylase inhibitory

Acknowledgment

The authors are grateful to The Tertiary Education Trust Fund (TETFUND), Nigeria for Grant given to S. M. Akoro to carry out this work at the University of Iowa, Iowa City USA. S.M Akoro also acknowledges the support of the University of Ibadan, Ibadan, Nigeria and Lagos State Polytechnic, Ikorodu, Lagos, Nigeria.

Disclosure statement

The authors declare that they have no conflict of interest.

Additional information

Funding

This work was supported financially by The Tertiary Education Trust Fund (TETFUND), Nigeria.