In vitro antibacterial activity of Sri Lankan orthodox black tea (Camellia sinensis L.) belonging to different agro-climatic elevations

摘要

Objective:To investigate the antibacterial properties of three grades of orthodox Sri Lankan black tea belonging to the three agro-climatic elevations. Methods: Methanloic extracts of orange pekoe (OP), broken orange pekoe fannings (BOPF) and Dust No. 1 belonging to three agro-climatic elevations (low, mid and high grown) were made and testedin vitro (concentration: 300μg/disc) against Gram-positive pathogenic bacteria,Staphylococcus aureus(ATCC25923) (S. aureus) andBacillus cereus (ATCC11778) (B. cereus), and two Gram-negative bacteriaPseudomonas aeruginosa (ATCC9027) (P. aeruginosa) andEscherichia coli (ATCC35218) (E. coli), using agar disc diffusion assay. Gentamycin (10μg/disc) was used as the positive control and methanol as the negative control. Minimum inhibitory concentration (MIC) values were evaluated, using micro dilution method. Results: None of the tea extracts exerted an antibacterial action againstP. aeruginosa andE. coli. In contrast mild to moderate antibacterial activity was exerted againstS. aureus andB. cereus. Further gentamycin exhibited strong antibacterial activity against all the four bacterial species. Further lowMIC values were evident for tea samples against the two Gram-positive bacteria. The order of anti-bacterial activity for tea extracts was Dust No. 1 >BOPF >OP. Conclusions: It is concluded that Sri Lankan orthodox black tea belonging to Dust No. 1, BOPF, andOP pocessin vitro antibacterial activity againstS. aureus andB. cereus but not against Gram-positive bacteriaP. aeruginosa andE. coli.