Composition Analysis and Inhibitory Effect against α-Amylase and α-Glucosidase of Acorn Kernel Extractions

In order to explore the component and inhibitory effects of extractions of acorn kernel on α-amylase and α-glucosidase, the ethyl acetate、N-butanol and water extractions of Quercus variabilis BI acorn kernelwere obtained by ultrasonic-assisted solvent extraction and separation. The composition of the extractions were analyzed by using UV spectroscopy, and high performance liquid chromatography (HPLC). The inhibitory effects of the extractions on α-amylase and α-glycosidase were investigated by using enzyme inhibition measurement, inhibition kinetics and fluorescence quenching. The results showed that three acorn kernel extractions were highly similar in chemical composition and were mainly tannin. The ethyl acetate extraction contained 9 different substances include epicatechin gallate, gallate and gallocatechin gallate and epigallocatechin gallate. N-butanol extraction contained 16 kinds of substances such as epicatechin gallate、gallocatechin and gallocatechin gallate.Water extraction contained 21 different substances include gallic acid and chlorogenic acid. The three extractions had obvious inhibitory effects on α-amylase and α-glycosidase, the half inhibitory concentrations (IC₅₀) of ethyl acetate, n-butanol, and water extractions on α-amylase were 1.047, 1.122 and 4.031 mg/mL respectively. The IC₅₀ values on α-glucosidase were 0.014, 0.028 and 0.037 mg/mL respectively. The inhibition of three extractions were mainly mixed and reversible, and the fluorescence quenching was mainly static quenching, and dynamic quenching was auxiliary.