Abstract
BackgroundNatural products have being used as potential inhibitors against carbohydrate-hydrolyzing enzymes to treat diabetes mellitus. Chinese dark tea has various interesting bioactivities. In this study, the active compounds from Qingzhuan dark tea were separated and their anti-diabetic activity was examined using an in vitro enzymatic model.MethodsThe chloroform, ethyl acetate, n-butanol, sediment and residual aqua fractions of a Chinese dark tea (Qingzhuan tea) were prepared by successively isolating the water extract with different solvents and their in vitro inhibitory activities against α-glucosidase were assessed. The fraction with the highest inhibitory activity was further characterized to obtain the main active components of Qingzhuan tea.ResultsThe ethyl acetate fraction had the greatest inhibitory effect on α-glucosidase, followed by n-butanol, sediment and residual aqua fractions (with the IC50 values of 0.26 mg/mL, 2.94 mg/mL, 3.02 mg/mL, and 5.24 mg/mL, respectively), mainly due to the high content of polyphenols. Among the eight subfractions (QEF1-8) isolated from the ethyl acetate fraction, QEF8 fraction showed the highest α-glucosidase inhibitory potential in a competitive inhibitory manner (the Ki value of 77.10 μg/mL). HPLC-MS analysis revealed that (−)-epigallocatechin gallate (EGCG) and (−)-epicatechin gallate (ECG) were the predominant active components in QEF8.ConclusionThese results indicated that Qingzhuan tea extracts exerted potent inhibitory effects against α-glucosidase, EGCG and ECG were likely responsible for the inhibitory activity in Qingzhuan tea. Qingzhuan tea may be recommended as an oral antidiabetic diet.
Highlights
Natural products have being used as potential inhibitors against carbohydrate-hydrolyzing enzymes to treat diabetes mellitus
Results and discussion α-Glucosidase inhibitory activity of Qingzhuan tea extracts α-Glucosidase plays a central role in modulating postprandial hyperglycemia, which breaks down α-1,4-glucosidic linkages of disaccharides, resulting in simpler sugars
The crude water extract of Qingzhuan tea was divided into five fractions by polarity and the α-glucosidase inhibitory activities of these fractions were detected using pNPG as the reaction substrate
Summary
Natural products have being used as potential inhibitors against carbohydrate-hydrolyzing enzymes to treat diabetes mellitus. Chinese dark tea has various interesting bioactivities. The active compounds from Qingzhuan dark tea were separated and their anti-diabetic activity was examined using an in vitro enzymatic model. Diabetes has become a major health problem in the world. It is a metabolic disease characterized by a high blood glucose level and can cause other health complications, such as cardiovascular disease, neuropathy, high blood pressure, weakness, gangrene, retinopathy, nephropathy and other dysfunctions [1]. One of the therapeutic approaches is focused on suppressing the glucose production from carbohydrates by inhibiting digestive enzymes, such as α-amylase and α-glucosidase [2, 3].
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