Prokinetic effect of black tea on gastrointestinal motility

The gastrokinetic effects of hot water extract of black tea [Camellia sinen sis, (L) O. Kuntze (Theaceae)] on gastrointestinal motility were studied bo th in vivo and in vitro. The extract significantly accelerated the gastroin testinal transit (GIT) in vivo in mice. These facilitatory effect was reduc ed after pretreatment with atropine, hemicholinium-3, morphine, indomethaci n, McN-A-343 and L-arginine. In guinea pig ileum, the extract facilitated t he peristaltic reflex in response to pressures in normal preparation. The b lack tea extract and L-NMMA (nitric oxide synthase inhibitor) significantly reduced the electrical field stimulated nonadrenergic, noncholinergic (NAN C) relaxation of isolated rat fundal strips. The extract markedly enhanced the tonic ('hump') responses to transmural stimulation in longitudinal musc le of guinea pig ileum which was unaltered in the presence of atropine. The se findings suggest a cholinergic involvement and a partial role of prostag landin and nitric oxide in the mechanism of action of black tea extract on gastrointestinal motility. To determine the effective constituents in black tea responsible for this activity, the effect of black tea polyphenols on GIT were also studied. Thearubigin fraction (but not theaflavin) accelerate d GIT significantly which suggests its involvement in the prokinetic effect of black tea.