School of Health Science and Technology

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Browsing School of Health Science and Technology by Subject "Catechins"

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    Antimutagenic effect of Kenyan Tea cultivars in a bacterial test system
    (2014) Mbuthia, Karori; Wachira, Francis; Ngure, Raphael; Mireji, Paul O; Wachira, Sabina
    The antimutagenic effects of the aqueous tea extracts from Kenyan black, green and purple cultivars were evaluated by the Ames te st using Salmonella typhimurium tester strains TA 1538. Results obtained showed that tea had no toxicity or mutagenic activity at a concentration of 20% (w/v) unlike the mut agen sodium azide. However, using the formulae, percentage inhibition = [1 - T/M] ×10 0 where T is number of revertants per plate in presence of mutagen and test sample and M is number of revertants per plate in positive control, tea extracts had a significant (P<0.05) antimutagenic activity where the percent inhibition was 65% for green te a, 38% for purple tea and 19.17% for black tea. This was attributed to the radical scavenging activity of polyphenols. There is need therefore to carry out further research to help understand the precise mechanism of action especially for black and purple teas, and to explore other beneficial effects that these polyphenols may have, before they can be adopted for therapeutic use.
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    Polyphenolic composition and antioxidant activity of Kenyan Tea cultivars
    (2014) Karori, SM; Wachira, FN; Ngure, RM; Mireji, PO
    Polyphenolic fractions in tea are potent bioactive mo lecules. In this study, the polyphenolic composition of 25 different types of Kenyan tea cultivars was de termined using the HPLC and the Folins Ciocalteus spectrophotometric methods. Total Polyphenols, Total Ca techins, individual catechins and Antioxidant Activity were significantly (P<0.05) different among tea varieties, with green tea had the highest levels of Total Polyphenols ranging from (19.70-26.12%), TC (8.51%-17.60%), indivi dual catechins, and AA (86.65-94.50%). In vitro bioassay carried out using 2, 2’-di phenyl picrylhydrazyl radical showed epigallocatechin gallate was the most potent catechin and the most potent in antioxidant activity (r=0.968***). Epigallocatechin (r=0.659***, p<0.001), Epicatechigallate (r=0.454*, p<0.001) and Epicatechin (EC) (r=0.780***, p<0.001) showed signifi cant (p<0.05) antioxidant activity. Black tea contained high levels of Theaflavins and Thear ubigins (2.072% to 17.12%), respectively) which accounted for its antioxidant activit y (r=0.803*** and r=0.859***, respectiv ely). Gallic acid also showed significant (r=0.530*) contribution to the antioxidant activity in black tea. Data obtained from this study reveals that different Kenyan tea cultivars have different polyphenolic co mposition which imparts on their unique biochemical qualities. Gr een and white tea products are rich in catechins, black tea products are rich in TFs and TRs while purple teas are rich in anthocyanins