Comparison of antidiabetic potential of (+) and (-)-hopeaphenol, a pair of enantiomers isolated from Ampelocissus indica (L.) and Vateria indica Linn., with respect to inhibition of digestive enzymes and induction of glucose uptake in L6 myotubes

The remarkable alpha-glucosidase inhibition exhibited by the acetone extract of the rhizome of Ampelocissus indica (L.) and stem bark of Vateria indica Linn. (IC50 23.2 and 1.47 mu g mL(-1)) encouraged us to isolate the phytochemicals from these plants. (+) and (-)-hopeaphenol (1) and (2) were isolated from A. indica (L.) and V. indica Linn. respectively. Compounds 1 and 2 displayed IC50 values of 21.21 +/- 0.987 and 9.47 +/- 0.967 mu M in an alpha-glucosidase inhibitory assay. The effect of glucose uptake performed by 2-NBDG in L6 rat skeletal muscle cells using flow cytometry (BD FACS Aria II, USA) showed potent glucose uptake by (+) and (-)-hopeaphenol of 31% and 26.4%, respectively. The data from an MTT cell viability assay revealed that the compounds are not toxic to the cells up to 200 mu M. Molecular docking studies show that the compounds bind effectively to the active sites of the proteins 1BVN, 3A4A and 3AJ7, which supported the observed alpha-glucosidase inhibition. The structures of these compounds were determined by the analysis of various spectroscopic data including HRMS-ESI, 2D NMR, CD spectroscopy, optical activity and were unequivocally established by single crystal X-ray crystallography. Herein we are reporting the phytochemicals from Ampelocissus indica (L.) and their antidiabetic activities for the first time.