Therapeutic value of organic and conventional teas in Sri Lanka against microbial agents

Abstract

Due to its naturally occurring medicinal ingredients known as polyphenols, tea attracts the interest of the pharmaceutical and scientific disciplines. Besides the established antioxidant activity, many phenolic compounds in tea exhibit significant antimicrobial activity. Environmental factors and crop management substantially influence the amount and activity of polyphenols available in tea leaves. In Sri Lanka, there are six main agro-ecological regions where tea is grown using either conventional or organic management. Present study focused to determine the effects of tea production system and their growing region on polyphenol content and antimicrobial properties of made tea. Fresh leaf samples were collected from randomly selected tea estates each for organically certified and conventional from major tea growing regions in Sri Lanka. They were manufactured into CTC black tea using a miniature system. Polyphenol content was assessed by ISO standard method, while the anti-bacterial and anti-fungal properties were evaluated using disk diffusion technique against Escherichia coli ATCC 25922 and clinical pathogen of Aspergillus niger. Polyphenol content, anti-bacterial and anti-fungal properties were significantly different (P<0.05) between the tea production systems and among the growing regions, where organic tea had higher polyphenol content, anti-bacterial and anti-fungal properties than conventional teas. The Southern region tea had greater anti-bacterial and anti-fungal properties probably due to the high polyphenol content, while it was the lowest in Uva region. In conclusion, this research presents preliminary evidence that Sri Lankan teas grown and managed organically have superior antimicrobial properties over conventional teas. To confirm the findings, more investigation using time series measurement in all tea-growing regions is suggested.