Pistagremic acid, a glucosidase inhibitor from Pistacia integerrima

Pistacia integerrima Stewart in traditionally used as folk remedy for various pathological conditions including diabetes. In order to identify the bioactive compound responsible for its folk use in diabetes, a phytochemical and biological study was conducted. Pistagremic acid (PA) was isolated from the dried galls extract of P. integerrima. Strong alpha-glucosidase inhibitory potential of PA was predicted using its molecular docking simulations against yeast alpha-glucosidase as a therapeutic target. Significant experimental alpha-glucosidase inhibitory activity of PA confirmed the computational predictions. PA showed potent enzyme inhibitory activity both against yeast (IC50: 89.12 +/- 0.12 mu M) and rat intestinal (IC50: 62.47 +/- 0.09 mu M) alpha-glucosidases. Interestingly, acarbose was found to be more than 12 times more potent an inhibitor against mammalian (rat intestinal) enzyme (having IC50 value 62.47 +/- 0.09 mu M), as compared to the microbial (yeast) enzyme (with IC50 value 780.21 mu M). Molecular binding mode was explored via molecular docking simulations, which revealed hydrogen bonding interactions between PA and important amino acid residues (Asp60, Arg69 and Asp 70 (3.11 angstrom)), surrounding the catalytic site of the alpha-glucosidase. These interactions could be mainly responsible for their role in potent inhibitory activity of PA. PA has a strong potential to be further investigated as a new lead compound for better management of diabetes. (C) 2012 Elsevier B.V. All rights reserved.