Comparative assessment of total polyphenols, antioxidant and antimicrobial activity of different tea varieties of Bangladesh

Objective: To determine the total polyphenol content, antioxidant activity and antibacterial properties of the extracts of different Bangladeshi tea varieties such as flowery broken orange pekoe, broken orange pekoe, red dust and green tea. Methods: Total phenolic and flavonoid contents were determined by Folin–Ciocalteu and aluminum chloride colorimetric assay, respectively. The antioxidant capacity was determined by ferric ion reducing antioxidant power and phosphomolybdenum method. Antibacterial activity was evaluated by disc diffusion method in agar plate and subsequently, the minimum inhibitory concentration was determined by broth dilution method. Results: Total phenolic and flavonoid contents were significantly higher (P < 0.05) in green tea compared to other three black tea varieties. The green tea also showed a higher free radical scavenging and antioxidant activities than all the other tea varieties tested (P < 0.05). In addition, the extracts of all four tea varieties showed inhibitory activity against several pathogenic bacteria and also the same trend of higher antimicrobial activity of green tea than other tea varieties was observed. Conclusions: Taken together, the results of this study demonstrated that Bangladeshi tea, especially the green tea, may act as a substitute for natural antioxidants and as a promising antibacterial agent for beneficial influence in human health