Evaluation of green tea extract as a safe personal hygiene against viral infections

Lee, Yun Ha; Jang, Yo Han; Kim, Young-Seok; Kim, Jinku; Seong, Baik Lin

Based on the previous report that ascorbic acid stabilized green tea catechins [35] , we examined the effects of the addition of common food preservatives such as ascorbic acid, citric acid, and sodium benzoate on the viral inactivating activity of GTE. 0.01%, 0.05%, and 0.1% of GTE solutions were supplemented with 2% citric acid, 0.1% sodium benzoate, and 0.2% ascorbic acid (GTEmix), and the mixtures were stored at 25°C or 37°C for six h-56 days. The GTE-mix solutions taken at various time-points were incubated with 10 6 PFU of PR8 virus for six h at 25°C for viral inactivation. The results show that, on a short-term period up to one week, the potency of the antiviral activity was compromised, but still enabled the reduction of the viral titers by 1-6log 10 depending on GTE-mix concentrations. The reduction of the antiviral potency was more apparent at lower temperature of 25°C (Fig. 3a) , and at lower concentrations of GT-mix of 0.01% and 0.05% (Fig. 3a, b) . The data also showed that, in the presence of an antioxidant such as ascorbic acid, the potency of GTE-mediated antiviral activity was significantly reduced. For example, the antiviral activities of 0.1% GTE-mix solutions stored at both temperatures were not as strong as 0.1% GTE that completely inactivated the virus (Fig. 2a-c) . Likewise, 0.05% and 0.01% GTE-mix solutions also demonstrated considerably compromised antiviral activities, as compared to the same concentrations of GTE solutions (Fig. 2b & c) . The reduced antiviral activities of GTEmix solutions were more pronounced when stored for relatively short periods less than one week. Interestingly, however, the antiviral activities of 0.1% GTE-mix stored at 25°C became complete after 1 day of storage, and 0.01% and 0.05% GTE-mix also steadily restored their antiviral activities at 14 days to the similar levels with the same concentrations of GTE (Figs. 2b and 3a) . The similar phenomena were observed in the GTE-mix solutions stored at 37°C. All the GTE-mix solutions stored for less than 14 days exhibited reduced antiviral activities but restored their activity to the similar levels to those of the same concentrations of GTE solutions at 14 days, and, notably, remained potent up to 56 days (Figs. 2c and 3b). Thus, storage time-dependent inactivating activities of GTE-mix solutions were in clear contrast to those of GTE solutions, where the initial antiviral strength was high for up to two weeks but exhausted over prolonged storage (Fig. 2) . None of the individual supplements nor their mixture showed inactivating Fig. 3 Maintenance of viral inactivation activity of GTE solution with supplements. 0.01, 0.05, and 0.1% GTE solutions were incubated at 25°C (a) or 37°C (b) in the presence of 2% citric acid, 0.1% sodium benzoate, and 0.2% ascorbic acid (GTE-mix). The GTE-mix solutions incubated for different times were mixed with 10 6 PF of PR8 virus for six h at 25°C for viral inactivation. Residual viral titers were determined by plaque assay on MDCK cells. As a control, the virus was incubated with PBS, and the viral titer was indicated by upper dashed lines. c As another controls, the virus was treated with the individuals of the supplement or with the mixture of three agents. Data are the mean of two independent experiments. Detection limit of plaque assay is 5, and error bars indicate the SD activity against the viruses (Fig. 3c) , indicating that the inactivation was solely due to the GTE. The results suggest that antioxid