Browsing by Author "Abeywickrama, K.R."

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    Oral diuretic activity of hot water infusion of Sri Lankan black tea (Camellia sinensis L.) in rats.
    (pharmacogn magazine, 2010) Abeywickrama, K.R.; Ratnasooriya, W.D.; Amarakoon, A.M.
    BACKGROUND: Black tea [Camellia sinensis (L.) O. Kuntze (family: Theaceae)] has been used by Sri Lankan traditional practitioners to promote diuresis. However, the type and grade of tea is not specified. MATERIALS AND METHODS: THIS STUDY INVESTIGATES THE DIURETIC ACTIVITY OF BLACK TEA INFUSION (BTI) IN RATS USING BROKEN ORANGE PEKOE FANNINGS (BOPF) GRADE FROM MAJOR AGROCLIMATIC ELEVATIONS: high-, mid-, and low-grown. Different concentrations of BTI, furosemide (positive control), and water (vehicle) were orally administered to starved (18 h) male rats (n = 9/group), then hydrated. Acute and chronic (28 days) diuretic activities were assessed by measuring cumulative urine output at hourly intervals for 6 h. Electrolyte levels (Na(+), K(+), Ca(2+), H(+), Cl(-), HCO(3) (-)), pH, osmolarity of urine, and glomerular filtration rate (GFR) of treated rats were determined. RESULTS: Administration of BTI induced a significant (P < 0.05) and dose-dependent diuretic activity, which varied with the tea produced in different agroclimatic elevations. Diuretic activity had a rapid onset (1(st) h), peaked at 2(nd) h and maintained up to 4(th) h (except the low dose). Furthermore, there was a dose-dependent increase in micturition frequency, which peaked at 2(nd) h. A close association between the caffeine content of tea and diuretic activity was evident. BTI-induced diuresis was accompanied with an increased urine Na(+) level and GFR. The diuretic activity of BTI was mediated via multiple mechanisms: inhibition of both aldosterone secretion (with increased Na(+)/K(+) ratio) and carbonic anhydrase [with decreased Cl(-)/(Na(+) + K(+)) ratio] and via thiazide type of diuretic action (evaluated with increased Na(+)/Cl(-) ratio). CONCLUSION: The Sri Lankan BOPF grade black tea possesses mild oral diuretic activity whose efficacy differs with the agroclimatic elevation of production. Furthermore, it supports the traditional claim that the black tea acts as a diuretic.
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    Oral hypoglycaemic, antihyperglycaemic and antidiabetic activities of Sri Lankan Broken Orange Pekoe Fannings (BOPF) grade black tea (Camellia sinensis L.) in rats.
    (Journal of Ethnopharmacology, 2011) Abeywickrama, K.R.; Abeywickrama, W.D.; Amarakoon, A.M.
    ETHNOPHARMCOLOGICAL RELEVANCE: Sri Lankan traditional practitioners recommend the consumption of black tea infusion (BTI) made from Camellia sinensis L. plant for regulation of glycaemia. However, they do not specify the grade of tea and their origin (i.e., agroclimatic elevation) and as such many prediabetics and milddiabetics use BOPF grade tea. AIM OF THE STUDY: This study examines the blood glucose lowering potential of Sri Lankan BOPF grade tea and its potency with respect to agroclimatic elevations. MATERIALS AND METHODS: Unblended orthodox BOPF grade tea samples were collected from high-, mid- and low-grown agroclimatic elevations in Sri Lanka. Different concentrations of warm BTI (60, 120 and 480 mg/ml), tolbutamide (reference drug: 22.5mg/kg body weight) and water (control) were orally administered to different groups of rats, and hypoglycaemic and antihyperglycaemic activities were assessed. Antidiabetic activity was determined using streptozotocin induced diabetic rats. Mechanisms of blood glucose lowering actions were investigated using several standards techniques. RESULTS: BTI exhibited significant (P<0.05), dose-dependent and marked hypoglycaemic and antihyperglycaemic activities with quick onset. These effects did not differ with respect to agroclimatic elevation, although there were differences in the content of phyto-constituents. BTI also showed marked and quick antidiabetic activity. BTI inhibited intestinal glucose absorption and impaired ?-glucosidase and ?-amylase activities. BTI possessed insulinomimetic action, ability to improve insulin sensitivity and in vivo antioxidant activity. Notably, BTI was nontoxic. CONCLUSIONS: BTI of Sri Lankan BOPF grade tea has oral hypoglycaemic, antihyperglycaemic and antidiabetic actions which are mediated via multiple mechanisms. This study also indicates that, BOPF grade tea of any agroclimatic elevations in Sri Lanka could be used in the regulation of glycaemia.