Blood Glucose Level Lowering Activity of Sri Lankan Black Tea brew (Camellia sinensis) in rats

This study examined the blood glucose level lowering ability of black tea brew (BTB) of Sri Lankan Camellia sinensis (L.) O. Kuntze (Family: Theaceae). This was tested in normoglycaemic and streptozotocin induced diabetic rats using high grown Dust grade No: 1 tea (doses used: 84 mg/ml, equivalent to 1.5 cups; 168 mg/ml, equivalent to 3 cups; and 501 mg/ml, equivalent to 9 cups, orally). The results show that BTB possess promising and significant (P < 0.05) hypoglycaemic (both in normoglycaemic fasted rats and non fasted rats), antihyperglycaemic (in terms of improved glucose tolerance test), and antidiabetic (when tested in streptozotocin induced diabetic rats) activities. BTB (only highest dose tested) also exhibited alpha-glucosidase inhibitory activity (in terms of sucrose tolerance test) inhibited glucose absorption from the lumen of small intestine and possessed marked antioxident activity in vitro (in terms of DPPH assay). On the other hand, the highest dose failed to increase insulin output and glycogen content in liver and skeletal muscle. It is concluded that BTB made from Sri Lankan black tea has blood glucose lowering activity in both normoglycaemic and diabetic status.