INFLUENCE OF GALLIC AND TANNIC ACIDS ON THE ANTIOXIDANT, ALPHA AMYLASE AND ALPHA GLUCOSIDASE INHIBITORY PROPERTIES OF ACARBOSE

Abstract

In this study, gallic acid (GA) and its octa-polymeric form- tannic acid (TA), which are two phenolic acids abundantly found in plant foods such as vegetables, fruits and legumes, were investigated for their influence on hyperglycemic and antioxidant properties of acarbose (AC). AC an antidiabetic drug with associated unpleasant side effects in vitro and in vivo in Drosophila melanogaster. Combinations of AC (1 mg/ml) and either of GA or TA (1 and 5 mg/ml) were assessed for their α-glucosidase and α-amylase inhibitory effects as markers of antihyperglycemic properties, as well as their free radicals scavenging, Fe2+ chelating and malondialdehyde (MDA) production inhibitory effects (in vitro). Furthermore, wild type D. melanogaster cultures were raised on diets containing AC, GA, TA and their various combinations (AC + 0.2 mg/g GA or TA and AC + 2.0 mg/g GA or TA) for seven days. Thereafter, flies were homogenized and homogenates’ glucose concentration, as well as α-glucosidase and α-amylase activities were determined. The results showed that GA and TA at 5 mg/ml significantly increased the α-glucosidase and α-amylase inhibitory effects of AC in vitro (P<0.05). In addition, GA and TA significantly increased the free radical scavenging abilities and inhibitory effect of AC on MDA production. In D. melanogaster, it was observed that flies raised on diets containing AC, GA and TA, as well as their various combinations had significantly lower (P<0.05) α-glucosidase and α-amylase activities in whole flies tissue homogenates compared to control flies. These could justify the observed reduction in the glucose concentration in these fly groups compared to the control flies. Therefore, this study has revealed that GA and TA could improve the antihyperglycemic and antioxidant properties of AC and hence, combinations of diets rich in GA and TA with AC could offer improved combinatory therapy for the management of type 2 diabetes mellitus.