Antibacterial and Sporicidal Activity Evaluation of Theaflavin-3,3′-digallate

Theaflavin-3,3′-digallate (TFDG), a polyphenol derived from the leaves of Camellia sinensis, is known to have many health benefits. In this study, the antibacterial effect of TFDG against nine bacteria and the sporicidal activities on spore-forming Bacillus spp. have been investigated. Microplate assay, colony-forming unit, BacTiter-Glo(TM), and Live/Dead Assays showed that 250 µg/mL TFDG was able to inhibit bacterial growth up to 99.97%, while 625 µg/mL TFDG was able to inhibit up to 99.92% of the spores from germinating after a one-hour treatment. Binding analysis revealed the favorable binding affinity of two germination-associated proteins, GPR and Lgt (GerF), to TFDG, ranging from −7.6 to −10.3 kcal/mol. Semi-quantitative RT-PCR showed that TFDG treatment lowered the expression of gpr, ranging from 0.20 to 0.39 compared to the control in both Bacillus spp. The results suggest that TFDG not only inhibits the growth of vegetative cells but also prevents the germination of bacterial spores. This report indicates that TFDG is a promising broad-spectrum antibacterial and anti-spore agent against Gram-positive, Gram-negative, acid-fast bacteria, and endospores. The potential anti-germination mechanism has also been elucidated.