Oral diuretic activity of Sri Lankan low grown orange pekoe grade black tea (Camellia sinensis l.) In rats..

Author(s): Wanigasekara Daya Ratnasooriya, Tharaka Bhanuguptha Sri Muthunayake, Edirisinghege Kanishka Indeesha, Chatura Dayendra Tissa Ratnasooriya

Abstract

In Sri Lankan ethnomedicine, black tea is claimed to be a diuretic. However, the grade of the tea is not specified. The aim of this study was to investigate the diuretic potential of Sri Lankan low grown orthodox whole leaf grade black tea (Camellia sinensis (L) O. Kuntz ; Family: Theaceae) using Orange Pekoe (O.P.) grade tea. Different doses of black tea brew (BTB) of O.P. grade tea [111 mg/kg (equivalent to 0.75 cups, N=7), 223 mg/kg (equivalent to 1.5 cups, N= 15), 446 mg/kg (equivalent to 3 cups, N=15) and 1339 mg/kg (equivalent to 9 cups, N=12)] or water (control, N=16) or Furosemide (reference drug, N=15) were orally administered to previously starved (18h) but subsequently hydrated (15 ml of isotonic saline) rats and their cumulative urine output was monitored at hourly intervals for 6h. The results showed moderate (compared to Furosemide), dose dependent diuretic activity. The onset of the diuretic activity was very rapid (within 1h) with an equally rapid peak dieresis (1-2h), but with a short duration of action (up to 2h). EC50 value for the diuretic action was 509.18 mg/kg. The diuretic action was accompanied with significant (P<0.05) increase in urinary Na+ (Natiuresis), K+ (Kaliuresis), pH, glomerular filtration rate (GFR) (in terms of creatinine clearance), aldosterone secretion index, thiazide diuretic index, intra and extra cellular pH regulatory index and urinary alkali index, whilst the carbonic anhydrase inhibition index was significantly reduced. In contrast, urinary Cl-, and HCO3- levels, total dissolved solids, conductivity, density, and specific gravity remained unaltered. Overall, the results suggest that, Sri Lankan low grown O.P. grade black tea has moderate diuretic activity mediated via multiple mechanisms.

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