Ultrasound-assisted extraction of Gac (Momordica cochinchinensis Spreng.) leaves: Effect of maturity stage on phytochemicals and carbohydrate-hydrolyzing enzymes inhibitory activity

Abstract

Although phytochemical contents of Gac fruit have been extensively analyzed, information about the bioactive compounds and valorization of Gac leaves is limited. In this study, Gac (Momordica cochinchinensis Spreng.) leaves at different maturity stages (young: YL, mature: ML and old: OL leaves) were extracted during a 20 min of 150-W sonication process. Color, phytochemicals, antioxidant activity, and inhibitory effects against carbohydrate-hydrolyzing enzymes were assessed by colorimetric, high-performance liquid chromatography, and spectrophotometric methods, respectively. Results indicated a decrease in L* (lightness) and an increase in a* (greenness-redness) during maturation of leaves. The YL extract had the highest contents of phytochemicals with 4897.01 (mg gallic acid equivalent [GAE] per 100 gram dried weight [DW]), total phenolics, 592.81 (mg quercetin [QE]/100 g DW), total flavonoids, 34.77% α-amylase inhibitory activity, and 40.21% α-glucosidase inhibitory activity. Myricetin (43%), vitexin (22%), and esculetin (11%) were the major bioactive compounds detected in YL extract. Also, the superoxide dismutase (SOD)-like capacity of the extract decreased from 11,599.96 to 3,999.63 U/g DW during the transformation of YL to OL. Extract of Gac leaves was found to be a potential ingredient for food preservation and supplementation that could reduce postprandial hyperglycemia.