PHYTOCHEMICAL SCREENING AND ANTIMICROBIAL STUDIES OF GREEN, ORTHODOX AND BLACK KENYAN TEA

Abstract

This  study  evaluated  the  phytochemical  and  antimicrobial  activities  of  green, orthodox and black Kenyan tea on five microorganisms with the possible purpose of determining  their  pharmacological  significance/  medicinal  value.  The  in  vitro antimicrobial activities of three extracts of tea was done using humanly isolated strains  of  Staphylococcus  aureus,  Salmonella  typhimurium,  Escherichia  coli, Streptococcus faecalis, and, Candida albicans.  The assays were carried out by agar well diffusion. Streptomycin and cefadroxil served as the control drugs. Aqueous tea extracts were used for the assays. The aqueous tea extracts were found to be more effective against the tested bacteria than fungi at high concentration. Orthodox tea had no antimicrobial activity against Salmonella typhimurium and Candida albicans.  Extracts of green tea, orthodox and black tea showed activity on Staphylococcus aureus at concentrations ranging from 100‐200mgml‐1 having comparable diameters of zones of inhibition of 10.0±0.0, 4±0.2 and 6.5±0.0 respectively.  The first two tea extracts demonstrated activities on Escherichia coli and Streptococcus faecalis at concentrations ranging from 100‐400mgml‐1 with relatively close diameters of zones of inhibition of 14mm and 12mm respectively.  Only black tea inhibited the growth of Candida albicans at the MIC of 100mgml‐1 whereas, Salmonella typhimurium was inhibited by green tea and black tea extracts at the MIC of 200mgml‐1.  Black tea also inhibited  growth  of  Escherichia  coli,  but  at  concentration  ranging  from  200‐400mgml‐1 with diameter zones of inhibition from 3.5±0.0‐ 4.0±0.0 and a MIC of 150mgml‐1.  Phytochemical  screening  of  the  three  extracts  of  tea  showed  the presence of cardiac glycosides, alkaloids, saponins, flavanoids, terpenes and tannins. Green tea lacked anthraquinones while orthodox tea lacked cardenolides. Results were interpreted according to Kirby‐Bauer technique. The results obtained in this study provide preliminary evidence  of the significance of secondary metabolites of tea and and their pharmacological effects.