The objective of the present study was to determine the inhibitory properties of the infusions and decoctions of
four samples of Indian black tea (BT) and some of the tea flavonoids, gallic acid and caffeine, in vitro, against β-
glucuronidase, lipase,α-amylase and α-glucosidase. These enzymes are related to liver disorders, obesity and diabetes.
The phenolic constituents and caffeine content in the BT extracts were measured quantitatively by HPLC. It was noted
that both infusion and decoction of BT had β-glucuronidase inhibitory property close to that of silymarin. Epigallocatechin
gallate, epicatechin, and gallocatechin showed higher β-glucuronidase inhibitory activity than that of BT extracts and
silymarin. BT extracts also inhibited the enzyme lipase. Thearubigin, theaflavin, epigallocatechin gallate, epicatechin and
gallocatechin showed significant lipase inhibitory properties that were superior to the drug orlistat. The tea extracts, flavonoids
and gallic acid inhibited the activity of α-amylase and α-glucosidase. Theaflavin and catechin had α-amylase inhibitory
activity better than that of acarbose. This in vitro study reveals that BT extract and the phenolic components may
have potential benefit for controlling liver disorders, obesity and diabetes.
Keywords: α-amylase, α-glucosidase, β-glucuronidase, black tea, flavonoids, gallic acid, lipase.
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