Abstract
This study is aimed at assessing the inhibitory effect of teas on key enzymes (α-amylase and α-glucosidase) linked with type-2 diabetes and their antioxidant properties. Four samples of three brands were used; infusions of green tea (GT), 2 brands of black tea (BT), and a formulated herbal preparation for diabetes (ADT) (white tea, Radix Puerariae, Radix ophiopogonis, hawthorn berry, Chinese yam, and fragrant Solomon seal rhizome) were prepared and subsequently analyzed for their total phenol, ascorbic acid contents, antioxidant properties (2,2-Azizobis (3-Ethylbenzo-Thiazoline~6-sulfonate) “ABTS” scavenging ability and ferric reducing antioxidant property), and inhibition of pancreatic-α-amylase and intestinal-α-glucosidase in vitro. The study revealed that GT had the highest total phenol content, ascorbic acid content, ABTS∗ scavenging ability, and ferric reducing ability. Furthermore, all the teas inhibited Fe2+ and sodium nitroprusside induced lipid peroxidation in pancreas, with GT having the highest inhibitory effect. Conversely, there was no significant difference (P > 0.05) in the inhibitory effects of the teas on α-amylase and α-glucosidase. The antidiabetic property of the teas could be attributed to their inhibitory effect on carbohydrate hydrolyzing enzymes implicated in diabetes and their antioxidant activities.
Highlights
Diabetes mellitus (DM) is undoubtedly one of the most challenging health problems in the 21st century; statistics show that at 2011, 366 million people are suffering from DM, a figure expected to increase to 552 million people by 2030 [1]
DM is characterized by hyperglycemia associated with abnormal metabolism of carbohydrates, fats, and proteins resulting from endocrine defects in insulin action, secretion, or both [2]
The ascorbic acid contents of the tea brands as presented in Figure 1 revealed that green tea GT (2.18 ± 0.04 mg/g) was significantly (P < 0.05) higher in ascorbic acid than black teas (BT1: 1.26 ± 0.09 mg/g; BT2: 1.31±0.05 mg/g) and antidiabetic tea (ADT: 1.15±0.02 mg/g)
Summary
Diabetes mellitus (DM) is undoubtedly one of the most challenging health problems in the 21st century; statistics show that at 2011, 366 million people are suffering from DM, a figure expected to increase to 552 million people by 2030 [1]. The inhibition of alpha-amylase and alphaglucosidase, carbohydrate hydrolyzing enzymes, can significantly reduce postprandial hyperglycemia and are considered an important therapeutic strategy in the management of blood glucose level in type-2 diabetes [3]. Inhibition of these enzymes delays the breakdown of polysaccharides and glucose absorption, thereby reducing the amount of glucose in the blood [4]. There is a third kind mostly popular in Asia commonly referred to as white tea; it shares similar processing to green tea but differs only in the stage of maturity in which the tea leaves are picked/harvested.
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