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

The potential effect of antioxidants was also evaluated, in the form of mixture (GTE-mix) comprising ascorbic acid, citric acid, and sodium benzoate (common food preservatives). It is well documented that ascorbic acid is one of the strongest reductants and acts as an oxygen scavenger [41, 42] . Although our experimental condition using the ascorbic acid did not perfectly reflect anaerobic condition, our data clearly showed that the ascorbic acid delayed the GTE-mediated viral inactivation, most likely through inhibiting the autoxidation of catechins mediated by molecular oxygen. The data suggest that the potency of virucidal activity was compromised for the initial period of a week; the reduction of infectious viral titer for GTE and GTE-mix was 4-6 log 10 and 1-3 log 10 , respectively. However, the virucidal activity of GTE-mix persisted up to 8 weeks (Fig. 3a, b) , in clear contrast to GTE without additives where the virucidal activity become exhausted after two weeks (Fig. 2) . Thus, the combination of GTE with ascorbic acid as antioxidant resulted in a sustained virucidal activity for extended period. It should be noted that contrasting activities, pro-oxidant and anti-oxidant, have been documented with green tea catechins [35] . Moreover, it has been proposed that the catechins in green tea crosslink with cysteine residues in a protein through autoxidation process [43, 44] . Thus, it is likely that a strong antioxidant such as ascorbic acid prevents the oxidation of polyphenolic OH groups of the catechins into quinone, a prerequisite for oxidative crosslinking to viral proteins [45] . Our data show that the viral inactivating activity of GTE-mix recovered after 14 days of storage despite the presence of ascorbic acid and other supplements (Fig. 3a, b) . Investigation of the chemical or biological status of ascorbic acid as an antioxidant especially in the mixture with GTE during the storage could provide a possible explanation for this phenomenon. Intriguingly, the antiviral activities of 0.1% GTE-mix and those of lower concentrations of GTE-mix were differently affected by storage temperatures, as compared to those of GTE. After storage at 25°C, the antiviral activity of 0.1% GTE-mix was reduced mildly, whereas those of 0.05% and 0.01% GTE-mix were considerably dampened (Fig. 3a) . Conversely, after storage at 37°C, the reduction of antiviral activity was more pronounced in 0.1% GTE-mix than those in 0.05% and 0.01% GTE-mix (Fig. 3b) . Although, the addition of the supplements including antioxidant obviously influenced the changes in the antiviral kinetics, further detailed analyses would be required to address the issue. A recent report suggested that urea supplementation of alcohol-based disinfectants in the presence of citric acid may increase their antiviral effects against a number of viruses [46] . Whether supplementing GTE with such components may enhance the stability of antiviral effect of GTE remains to be further tested.