Abstract
Green tea, green tea polyphenols and epigallocatechin gallate (EGCG) are confirmed to have beneficial effects in the treatment of diabetes mellitus, and a possible mechanism can be ascribed to their inhibitory effect against α-amylase and α-glucosidase in the digestive tract. In this paper, we first investigated the combined inhibitory effect of green tea extracts, green tea polyphenols or EGCG with acarbose on α-amylase and α-glucosidase in vitro. Our results indicated that the interaction between green tea extracts (green tea polyphenols or EGCG) and acarbose was complicated. The combination of green tea extracts, green tea polyphenols or EGCG with acarbose had a synergistic effect on α-amylase and α-glucosidase at low concentrations and the combined effect turned out to be antagonistic at high concentrations according to the Combination Index (CI) values. These findings not only provided some significant quantitative values, but also provide some valuable implications for the combined use of acarbose and GTE (GTP or EGCG) in the treatment of diabetes mellitus.
Highlights
Diabetes mellitus is a seriously chronic disease accompanied by hyperglycemia which results in the disturbance of the metabolism and brings about attendant diabetic complications such as hypertension, cardiovascular disease and diabetic neuropathy [1]
The results (Table 1) showed that the IC50 values of green tea extracts (GTE), green tea polyphenols (GTP) and epigallocatechin gallate (EGCG) against α-glucosidase were 4.421 ± 0.018, 10.019 ± 0.017 and 5.272 ± 0.009, respectively, which were much lower than the IC50 of acarbose against α-glucosidase (4,822.783 ± 26.042) indicating that GTE, GTP, and EGCG strongly suppressed the α-glucosidase and that could possibly be utilized for the control of postprandial hyperglycemia
Our Combination Index (CI) analysis indicated that the combination of acarbose and GTE or GTP or EGCG produce a synergistic effect at certain concentrations
Summary
Diabetes mellitus is a seriously chronic disease accompanied by hyperglycemia which results in the disturbance of the metabolism and brings about attendant diabetic complications such as hypertension, cardiovascular disease and diabetic neuropathy [1]. Taking the current research and status into consideration, it could be hypothesized that combined drug and natural compound inhibitors of α-amylase and α-glucosidase could be very interesting due to their potential efficiency. Until recently little information is known about the interaction between acarbose, an effective first-line drug which has inhibitory activities against α-amylase and α-glucosidase, and green tea. The aim of this study is to determine whether green tea extracts (GTE), green tea polyphenols (GTP) or epigallocatechin gallate (EGCG) in combination with acarbose have additive, synergistic or antagonistic effects on the inhibition of α-amylase and α-glucosidase in vitro and to provide some insights on the intake of green tea, or its related extracts. Using a two-way experimental design, the effect of combinations of GTE, GTP, and EGCG and acarbose on α-glucosidase and α-amylase were studied and analyzed using the Chou and Talalay method, which is widely used to determine synergistic or antagonistic effects in combination studies
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