Anti-human rhinovirus activity of gallic acid possessing antioxidant capacity

Human rhinoviruses (HRVs) are a major cause of the common cold and until now there is no registered clinically effective antiviral chemotherapeutic agent for treatment of diseases caused by HRVs. Our previous report showed that gallic acid from Woodfordia fruticosa flowers possessed antioxidant activity. Many studies reported that antioxidants possess antiviral activities against various viruses. Therefore, we examined antiviral activity of gallic acid against HRVs and mode of its actions by observing the effect of gallic acid on HRV-induced cytopathic effect (CPE) and the infectivity of HRV particles, and then carried out a time-addition study. As a result, gallic acid actively inhibited HRV2 and -3 replications with antiviral activity more than 55% without cytotoxicity in human epitheloid carcinoma cervix (HeLa) cells at a concentration of 100 mug/mL. Also, ribavirin showed lower anti-HRV3 activity than gallic acid and similar anti-HRV3 activity to it. The addition of gallic acid to HRV-infected HeLa cells directly reduced the formation of a visible CPE. Furthermore, gallic acid did directly interact or activate with HRV particles. Collectively, we concluded that the inhibition of HRV production by gallic acid is mainly due to a general action as an antioxidant and the mode of action derived from the inhibition of virus absorption.