Bioactivity of Green Tea Kombucha: Polyphenol-Rich Ferment for Oxidative and Inflammatory Stress Modulation

Kombucha is a fermented tea beverage increasingly recognized for its health-promoting properties due to its richness in polyphenols, organic acids, and microbial metabolites. This study evaluated the antioxidant, anti-inflammatory, and antibacterial activities of green tea-based kombucha fermented for 14 days.

Biochemical assays revealed high levels of total polyphenols (4.97 mg GAE/mL), flavonoids (258.48 mg QE/mL), tannins (172.82 mg EC/mL), and flavonols (33.4 mg QE/mL). Antioxidant capacity was assessed using DPPH, ABTS, FRAP, and TAC assays. The extract showed strong radical scavenging activity, particularly in the ABTS and TAC assays, with IC₅₀ values of 3.44% and 0.52%, respectively.

Anti-inflammatory activity was evaluated through bovine serum albumin (BSA) denaturation inhibition. Interestingly, the highest inhibition was observed at the lowest concentration tested (0.18%), suggesting potential prooxidant effects at higher doses.

Antibacterial effects were tested against E. coli, P. aeruginosa, B. subtilis, and S. aureus using the agar diffusion method. Moderate inhibition was observed for P. aeruginosa and B. subtilis, with increased activity after longer fermentation.

These findings support green tea kombucha as a promising natural product with antioxidant, anti-inflammatory, and antibacterial properties, encouraging further exploration for therapeutic or functional food applications.