In vitro anti-diabetic activity of flavonoids and pheophytins from Allophylus cominia Sw. on PTP1B, DPPIV, alpha-glucosidase and alpha-amylase enzymes

Background: Ethno-botanical information from diabetic patients in Cuba led to the identification of Allophylus cominia as a possible source of new drugs for the treatment of type 2 diabetes mellitus (T2-DM). Experimental: Chemical characterization of the extracts from A. cominia was carried out using chromatographic and spectroscopic methods. The extracts were tested for their activity on PTP1B, DPPIV, alpha-glucosidase enzymes and alpha-amylase. Results: The flavonoid rich fractions from A. cominia inhibited DPPIV enzyme (75.3 +/- 2.33%) at 30 mu g/ml and produced a concentration-dependent inhibition against DPPIV with a Ki value of 2.6 mu g/ml. At 30 mu g/ml, flavonoids and pheophytins extracts significantly inhibited PTP1B enzyme (100 +/- 2.6% and 68 +/- 1% respectively). The flavonoids, pheophytin A and pheophytin B fractions showed significant concentration-dependent inhibition against PTP1B with Ki values of 3 mu g/ml, 0.64 mu g/ml and 0.88 mu g/ml respectively. At 30 mu g/ml, the flavonoid fraction significantly inhibited alpha-glucosidase enzyme (86 0.3%) in a concentration-dependent pattern with a Ki value of 2 mu g/ml. None of the fractions showed significant effects on alpha-amylase. Fatty acids, tannins, pheophytins A and B, and a mixture of flavonoids were detected in the methanolic extract from A. cominia. The identified flavonoids were mearnsitrin, quercitrin, quercetin-3-alloside, and naringenin-7-glucoside. Conclusion: The pharmacological effects of the extracts from A. cominia earlier observed in experimental diabetic models was confirmed in this study. Thus a new drug or formulation for the treatment of T2-DM could be developed from A. cominia.