Anxiolytic activity of hot water brew of Sri Lankan black tea (Camellia sinensis L.) in rats

Abstract

Some reputed traditional practitioners of Sri Lanka claim that consumption of black tea brew/ infusion (BTB) of Camellia sinensis (L) O. Kuntze (Theaceae) suppresses anxiety. But this claim has not been scientifically tested and proven. This study therefore investigated the anxiolytic potential of BTB of Camellia sinensis (with Sri Lankan high grown Dust grade No 1 black tea) in rats using three models of anxiety (hole-board; neophobia suppression of eating and drinking tests). Different doses of BTB (equivalent to 1.5, 3, 9, and 24 cups; one cup = 170 mL) or a single (equivalent to 3 cups) of green tea brew (GTB) of Japanese or Chinese varieties or 2 mL of water were orally administered to different groups of rats and anxiolytic effects were determined. The results showed that BTB has anxiolytic action with swift onset (within 1 h) and no accompanying unwanted side effects: muscle relaxation, motor incoordination, sedation or sleep promotion. The anxiolytic effect of BTB was however inferior to GTB. Further, decaffetnation of BTB did not impair its anxiolytic action indicating that anxiolysis was not mediated via caffeine. The anxiolytic action of BTB may be mediated mainly via L-thianine, amino acid (unique to tea) through GABA-ergic pathways. It is concluded that black tea has mild to moderate oral anxiolytic activity.