Inhibitory Properties of Combined Ethanol Seed Extract of P. guineense and T. conophorum on -Glucosidase Enzyme

Abstract

The study was aimed to evaluate the α-glucosidase inhibitory properties of combined ethanol seed extract of Piper guineense and Tetracarpidium conophorum (CEPGTC). In vitro inhibitory assay was conducted in accordance with standard methods. p-nitrophenyl--D-glucopyranoside (pNPG) was used as a substrate. Fixed amount of the enzyme was incubated with increasing concentrations of CEPGTC seed extract (20-100 μg/ml) at 37°C for 15 min. The continuous production of p-nitrophenol was determined by measuring the absorbances at 410 nm. Acarbose at varying concentration (20-100g/ml) was used as the positive control. The median Inhibitory Concentration (IC50) values were graphically determined as the half-maximal inhibitory from plots of percent inhibition against log inhibitor concentration and by non-linear regression analysis. The enzyme kinetics (pattern of Inhibition) was determined using the Michaelis Menten’s equation and Lineweaver-Burk plot. The result showed that there was inhibition in all concentrations evaluated. The IC50 values estimated were 2.9 μg/ml and 2.5 μg/ml for CEPGTC and acarbose respectively. However, The IC50 value for acarbose was significantly (p<0.05) different from CEPGTC which is an indication of acarbose as effective -glucosidase inhibitor thus, used as positive control. An enzyme kinetics studies from the Lineweaver-Burke plot showed that CEPGTC seed extract demonstrated an uncompetitive inhibition on α-glucosidase while acarbose exhibited non competive (mixed inhibition). The inhibitory response and mechanism of inhibition observed in this study showed that combined ethanol seed extract of Piper guineense and Tetracarpidium conophorum has the potential to reduce glucose turnover and improve Hyperglycemia.