In the present study, twelve different types of commercial tea samples were assayed to determine their phenolic composition and antioxidant activity. Reverse phase high performance liquid chromatography using a binary gradient system was used for the identification and quantification of individual catechins. Subsequently, total phenolic content was determined spectrophotometrically according to the Folin-ciocalteus method. Total theaflavins and thearubigins were also determined. The radical scavenging behavior of the polyphenols on 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) was also studied spectrophotometrically. The results showed that total polyphenols, total catechins and antioxidant activity were significantly (P<0.05) different in the commercial tea samples. Green tea had the highest levels of catechins, total polyphenols and total antioxidant activity. White tea (silvery tip) a rare specialty type of tea was not significantly different from green tea. Statistical analysis showed an essential catechin content influence of the tea extracts on antioxidant activity. Epigallocatechin gallate (EGCG) was the most potent catechin and the most potent in antioxidant activity (r = 0.989***). Epigallocatechin (EGC) (r = 0.787, P<0.001), epicatechin (EC) + catechin (+C) and epicatechigallate (ECG) also showed significant (P<0.05) antioxidant activity. Black tea contained high levels of theaflavins and thearubigins, which accounted for most of the antioxidant potential in this type of tea product (r = 0.930*** and r = 0.930*** respectively). These results suggest that conversion of catechins during black tea processing did not affect the free-radical potency of black tea. Gallic acid (GA) also showed significant(r = 0.530*) contribution to the antioxidant activity in black tea. Green, black and white tea products processed from Kenyan tea cultivars originally selected for black tea had significantly (P<0.05) higher antioxidant activity than green tea processed from tea cultivars from Japan and China. These results seem to suggest that the cultivar type is critical in determining the antioxidant potency of tea product and that black teas processed from suitable cultivars could be potent in antioxidant activity when compared to green teas.

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Background: Microbial resistance has become an increasing global problem and there is a need to find out novel potent antimicrobial agents with alternative modes of action as accessories to antibiotic therapy.Methods & Materials: This study investigated the antioxidant, antimicrobial and synergistic properties of tea polyphenols. The tea germplasm from Kenya, China and Japan that are grown in Kenya were characterized for their biochemical profiles. The total phenolic content, theaflavins and thearubigins content of different tea products used in this study were determined spectrophotometrically according to Folin-Ciocalteus and flavognost methods, respectively. The individual catechin contents were characterized by high performance liquid chromatography (HPLC) and identified according to their HPLC retention times, elution order and comparison with authentic standards. The antioxidant activity of tea polyphenols was determined spectrophotometrically on its ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. The agar disc diffusion method was used to screen for antimicrobial and synergistic activities of the tea liquors.Results: Black, green, purple coloured leaf and white (silvery tips) tea products characterized for their biochemical profiles differed significantly in the levels of total polyphenols, total catechins, catechins fractions, theaflavins and thearubigins (p≤0.05). Green, purple coloured leaf (aerated), black tea from terminal buds and white tea products analyzed in this study exhibited slightly higher antioxidant activity as compared to black tea. The different types of tea products assayed in this study exhibited significant influence on the inhibition zone diameters against bacteria and fungi exposed to the tea extracts. Methicillin and penicillinase resistant S. aureus ATCC 25923, C. albicans ATCC 90028 and a clinical isolate of C. neoformans were most susceptible to all tea extracts than E. coli and S. typhi. There was synergism between most tea extracts and penicillin G against methicillin and penicillinase resistant S. aureus ATTC 25923. Conclusion:This study suggests potential use of tea extracts as an antimicrobial agent.

The tea polyphenols have been shown to possess many medicinal properties including antifungal activity, but there have been few studies regarding antifungal activity. The antifungal activity of tea polyphenols was evaluated on Candida albicans ATCC 90028 and a clinical isolate of Cryptococcus neoformans employing the disc diffusion assay. The minimum inhibitory concentration (MIC) of the tea polyphenols against C. albicans ATCC 90028 and a clinical isolate of C. neoformans was determined. Tea polyphenols showed antifungal activity against C. albicans ATCC 90028 and a clinical isolate of C. neoformans and both demonstrated an MIC of 1 mg/ml after 24 h. Both fungus were found to be sensitive to tea all tea extracts (p<0.05). The inhibition zone diameters significantly (p<0.05) and positively correlated to the catechins (EGCG and EGC), total TFs and total TRs. The study reveals the antifungal properties of green, white and black tea products from Kenyan germplasm that may find therapeutic applications in future.