Effect of green tea kombucha fermentation on phenolic content and antioxidant activity in Vero cells

Kombucha, a fermented beverage, is gaining attention for its antioxidant potential. Here, we investigated the effects of green tea kombucha fermentation on the phenolic profile and in vitro antioxidant capacity, both in a standardized inoculum and an industrialized kombucha. Green tea showed higher phenolic content and antioxidant activity in cell-free assays. However, these advantages were not observed in VERO cells, where 200 μL∙mL^-1 of green tea induced adverse effects, higher than those caused by H₂O₂. Similarly, industrialized kombucha at a 200 μL·mL^-1 concentration exhibited reactive species generation and cell viability comparable to those of H₂O₂. In turn, green tea standardized kombucha, at all concentrations, mitigated the viability loss, reactive species generation, and DNA fragmentation caused by H₂O₂ in VERO cells. Therefore, our study demonstrated that standardized kombucha produced an improved, protective beverage, suggesting that control of the starter culture may be implicated in enhanced antioxidant capacity in VERO cells.