Evaluating bioactivities of the extracts prepared from a locally fermented tea

Abstract

Tea is one of the most well-known beverages in the world, particularly in Asia, and it comes in a variety of forms. Tea agriculture has a three thousand-year history in Vietnam, and the tea plant has provided several economic benefits to the country. In this study, a locally fermented tea used as the material was prepared as infusion and freeze-dried samples, which were used for the evaluation of antioxidant, antibacterial activity, and cytotoxicity activities. In the antioxidant evaluation, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical test was applied for assessment of tea extracts’ ability to scavenge free radicals at various concentrations, then the IC50 was calculated for comparisons. Both of the extracts had remarkable antioxidant activities, especially the distilled water extract showed the best antioxidant activity among the others with the lowest rate of IC50 at 400.9167 µg/ml. Moreover, the tea extracts were also tested on a Gram-negative bacterium (Escherichia coli) and a Gram-positive bacterium (Staphylococcus aureus) by applying the disc diffusion method. The results showed that extracts only had mild effect on S.aureus and had no effect on E.coli. In addition, the extracts were tested against the human liver cancer cell line (HepG2) using the sulforhodamine B (SRB) assay. Surprisingly, the freeze-dried extract was proven to have an extremely strong cytotoxic effect on the HepG2 cell line with 73.8% inhibition of the cell population, which was even significantly higher than that of the positive control (49.5%). This project generated the initial set of data on different bioactivities of extract prepared from a locally fermented tea. The result provided the promising health benefit of Vietnamese fermented tea