Alpha-amylase Inhibitory Compounds from Musa cavendishii

Aims: To investigate the ethyl acetate fraction from the methanol extract of the leaves of Musa cavendishii and to evaluate the alpha-amylase inhibitory activity of its isolated phytochemicals and their value as potential anti-obesity products.

Study Design: Isolation and identification of phytochemicals from the ethyl acetate fraction and investigation of their alpha-amylase inhibitory activity through In vitro screening and docking study.

Place and Duration of Study: Faculty of Pharmacy, Mansoura University, between June 2013 and July 2016.

Methodology: Different phytochemicals were isolated and purified using different chromatographic techniques from the ethyl acetate fraction of the extract of dried powdered leaves of Musa cavendishii. Elucidation of the structures of the isolated compounds was performed using different spectroscopic methods (1H NMR, 13C NMR, NOESY, HSQC and HMBC). Alpha-amylase inhibition assay was used to evaluate the inhibitory activity of the isolated compounds. Furthermore, docking study was conducted to get an insight about the binding mode of the active compounds within the active site of the target enzyme.

Results: (6S,9S)-roseoside 1-A was reported form the titled plant for the first time along with six reported compounds viz., (6S,9R)-roseoside 1-B, kaempferol-3-O-rutinoside 6, p-hydroxybenzoic acid 2, rutoside 7, catechuic acid 5, quercetin 4 and kaempferol 3. The diglucosides, kaempferol-3-O-rutinoside and rutoside exhibited better alpha-amylase inhibitory activity (80.45 and 98.0% inhibition, respectively) than the positive standard alph-amylase inhibitor (acarbose) used (57.0%) at a concentration of 50 µg/mL. In an agreement with the results of alpha-amylase inhibition assay, the docking results indicated that these two diglucosides 6 and 7, showed the highest binding scores (-8.16 and -7.68 kcal/mol) compared to positive standard acarbose (-5.40 kcal/mol).

Conclusion: This study showed that flavonoid diglucosides e.g. kaempferol-3-O-rutinoside and quercetin-3-O-rutinoside (rutoside) could be potential inhibitors for alpha-amylase and could be used as anti-obesity phytochemicals.