Alpha-amylase inhibitors from Thai medicinal herbs for treatment of diabetes

Abstract

Alpha-amylase inhibitors have been known as one of potent therapeutic drugs for treatment of non-insulin dependent diabetes mellitus (NIDDM). Thai medicinal herbs samples were extracted with aqueous methanol (10 ml/g fr.wt.) for 24 h at room temperature and subjected to porcine pancreatic α-amylase (PPA) inhibitory activity determination. Twenty-one of the 37 tested herb samples showed PPA inhibitory activity more than 50% and among these, 4 herb samples gave 90-100% PPA inhibition including leaves of guava, Psidium guajava L., (91.10%). The ethyl acetate partitioned fraction of guava leaves extract was purified using HPLC column: Inertsil PREP-ODS and the active fractions were structurally identified by FD-MS and 1H-NMR and proven to be tannins and catechin. In addition, 3-arabinopyranoside was also obtained from HPLC column: Develosil C-30 and its structure was identified by FAB-MS and 1H-NMR. The PPA inhibitory activity of tannin isolated from guava leaves extract was the most effective PPA inhibitor (100% PPA inhibition) while less activities were obtained from catechin (8% PPA inhibition) and 3-arabinopyranoside, respectively. This leads to potential possibility to develop the pharmaceutical products from guava leaves for treatment of NIDDM.