A dose of theanine equivalent of eight cups of back tea improves cognitive and neurophysiological measures of selective attention, to a degree that is comparable with that of caffeine. Theanine and caffeine seem to have additive effects on attention in high doses.

Background/Aims: The polyphenols catechins and theaflavins in black tea have been shown to possess many medicinal properties, including anticancer activity and some antifungal characteristics, but there have been few studies of their anti-Candida activity. In this paper we report the results of our study of the anti-Candida activity of tea polyphenols. Methods: The effects of 4 different concentrations of catechins and theaflavins were evaluated on 5 isolates each of 5 Candida species employing an agar diffusion growth inhibition assay. The minimum inhibitory concentration (MIC) of the polyphenols against C. albicans was determined. The post-antifungal effect (PAFE) of the polyphenols for C. albicans was investigated. C. albicans cells exposed to polyphenols were studied using a scanning electron microscope (SEM). Results: Both polyphenols showed anti-Candida activity against all tested Candida species and demonstrated a MIC of 6.25 mg/ml for C. albicans. C. glabrata was found to be the most sensitive species followed by C. parapsilosis, C. albicans, C. krusei and C. tropicalis (p < 0.05 for all). Significant intraspecies variations in sensitivity were noted among C. parapsilosis and C. tropicalis (p < 0.001) for both polyphenols. Theaflavins displayed standard PAFE while catechins showed a paradoxical PAFE with all isolates of C. albicans. SEM revealed considerable cell wall damage of C. albicans cells exposed to the polyphenols. Conclusion: The study reveals for the first time the anti-Candida properties of black tea polyphenols that may find therapeutic applications in future.

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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+, Ca2+, H+, Cl−, HCO3−), 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 (1st h), peaked at 2nd h and maintained up to 4th h (except the low dose). Furthermore, there was a dose-dependent increase in micturition frequency, which peaked at 2nd 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.

Studies were performed to investigate the effect of a polyphenol rich extract from black tea and vitamin E on bacterial lipopolysaccharide (endotoxin) induced IL-6 production, alterations in liver glutathione and antioxidant acute phase protein (caeruloplasmin) concentration, in rats fed on a synthetic diet for 21 days. In the vitamin E sufficient group a significantly lower IL-6 concentration than in vitamin E deficient animals was observed. Addition of tea extract to the diet produced a similar reduction in IL-6, but no synergism occurred in the presence of both vitamin E and tea extract. However, a significantly lower caeruloplasmin and a significantly higher liver glutathione concentration was observed in rats fed both substances. It is suggested that consideration of dietary components which alter antioxidant/oxidant status may contribute towards treatment of inflammatory/autoimmune diseases.