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Dual Virucidal and Direct Antibacterial Activities of a Commercial Green Tea Extract Preparation and EGCG: Potential Applications for Oral and Upper Respiratory Health

Year: 2026

Type: article

Abstract: Background/Objectives: Green tea-derived catechins, including epigallocatechin gallate (EGCG), possess diverse antimicrobial properties. This study investigated the dual antiviral and antibacterial activities of a commercially available green tea extract (cGTE) preparation and EGCG against influenza viruses and representative oral bacteria to evaluate their potential for oral and upper respiratory applications. Methods: The antiviral activities of the cGTE preparation and EGCG against influenza A virus strains H1N1 (A/Puerto Rico/8/1934) and H5N2 (mouse-adapted influenza A/aquatic bird/Korea/w81/2005) were evaluated by assessing virucidal activity, time-of-addition experiments, and inhibition of hemagglutinin (HA) and neuraminidase (NA) activities. Antibacterial activity was assessed following direct exposure of Gram-positive oral streptococci (Streptococcus mutans, S. salivarius, S. mitis, S. sanguinis, and S. sobrinus), Staphylococcus aureus, and Gram-negative Escherichia coli strains to the cGTE preparation or EGCG. Results: Both the cGTE preparation and EGCG exhibited concentration- and time-dependent virucidal activities against A/H1N1 and A/H5N2 viruses. Direct treatment of the viruses generally produced greater antiviral effects than cell pre- or post-treatment. Both treatments also inhibited HA and NA activities, suggesting that interference with viral surface-associated functions may contribute to their antiviral effects. In addition, the cGTE preparation and EGCG reduced bacterial viability following direct exposure, with EGCG showing strong direct antibacterial activity against oral Streptococcus species. Conclusions: The cGTE preparation and EGCG exhibited dual virucidal and direct antibacterial activities against influenza viruses and a range of oral bacteria. These findings support their potential as multifunctional antimicrobial agents for locally applied formulations targeting the oral and upper respiratory environments.

Source: Antibiotics

DOI: 10.3390/antibiotics15101007