Phytochemical screening, GC-MS analysis and in vitro inhibition of alpha-amylase and alpha-glucosidase activities by methanol extract of Psidium guajava leaves and fractions

Abstract

Decreasing post-prandial blood glucose levels by retarding the activities of principal carbohydrate-metabolizing enzymes such as α-amylase and α-glucosidase is one approach in the management of diabetes mellitus. The leaves of Psidium guajava are used to manage and control a number of diseases including diabetes mellitus. This study was aimed at evaluating in vitro, the inhibitory capabilities of the crude methanol extract, n- hexane, dichloromethane and aqueous fractions of the methanol extract of Psidium guajava leaves on the activities of α-amylase and α-glucosidase and also screening the phytochemical constituents and analyzing the bioactive components of the most potent fractions using Gas Chromatography - Mass Spectrometry (GC-MS) analysis. All fractions of the methanol extract had inhibitory effects on the activities of α-amylase and α-glucosidase with the dichloromethane fraction having the highest percentage inhibition on the activity of α-glucosidase, having 92.52% inhibition at 100μg/ml and the crude methanol extract had the highest percentage inhibition of α-amylase activity, having 89.2% inhibition at 100μg/ml. Phytochemical screening of the most potent fractions (crude methanol extract for α-amylase and dichloromethane fraction for α-glucosidase respectively) revealed the presence of phytochemicals such as flavonoids, glycosides, phenolic compounds and condensed tannins. Also, GC-MS analysis of the most potent fractions revealed the presence of compounds such as caryophyllene, phytol, squalene, and 2’,6’-dihydroxymethoxychalcone that have been reported to have antidiabetic activities. The results from this work therefore show the potential of the fractions of the methanol extract of Psidium guajava leaves in the management of diabetes mellitus.