In Vitro Inhibitory Effect on Carbohydrates Digestion and Antioxidant Potential of Garlic Scape (P06-076-19)

Inhibition of carbohydrate absorption from intestine is an efficient way to prevent type 2 diabetes. Some edible plants have shown the potential as anti-diabetic agents by inhibiting carbohydrate-digestive enzymes in intestine. In terms of edible plant's health effect, bioactive compounds’ stability during the process of digestive enzymes has been commonly questioned. Therefore, the objectives of this study were to 1) examine inhibitory effect of garlic scape (GS), the green flower head of garlic on carbohydrate-degrading enzymes and 2) investigate antioxidant activity and total phenolic content (TPC) of GS treated with intestinal digestive enzymes. GS extract (GSE) was prepared with 80% methanol (v/v) by homogenization, sonication, and filtration, and evaporation. α-glucosidase, maltase, glucoamylase, sucrase, α-amylase inhibitory activities were determined by measuring glucose hydrolyzed from nitrophenyl-glucopyranoside, maltose, starch, sucrose, and starch, respectively. To prepare gastrointestinal enzyme-digested GSE, GSE was digested with pepsin and a pancreatin-bile solution. GSE and gastrointestinal enzyme-digested GSE were assessed for TPC using a Folin-Ciocalteu reagent and for total antioxidant and radical scavenging activities by the following methods, phosphomolybdeum, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods, respectively. GSE (20 mg/ml) showed 30%, 50%, and 42% inhibition on α-glucosidase, maltase, and glucoamylase enzyme activities, respectively. GSE (50 mg/ml) showed 55.1% DPPH radical and 5782 mg vitamin C equivalent (VCE)/g ABTS radical scavenging activities. Total antioxidant activity of the GSE (1.5 mg/ml) exhibited 2.76 mg VCE/g. Consistent with its antioxidant property, the GSE showed a dose-dependent increase in TPC. Gastrointestinal enzymatic treatment resulted in approximately 46% reduction in DPPH and ABTS radical scavenging activity, total antioxidant activity, and TPC of the GSE. Garlic scape has the potential as a natural anti-diabetic agent. Garlic scape keeps beneficial effects after the process of intestinal digestive system. The work was supported by USDA.