Anti-human rhinovirus 2 activity and mode of action of quercetin-7-glucoside from Lagerstroemia speciosa.

Human rhinoviruses (HRVs) are a major cause of the common cold, but there is currently, no registered clinically effective antiviral chemotherapeutic agent for treatment of diseases caused by HRVs. In this study, we examined the antiviral activity of quercetin 7-glucoside (Q7G) from Lagerstroemia speciosa against human rhinovirus 2 (HRV2) using a cytopathic effect (CPE) reduction method. Furthermore, to elucidate the action of Q7G on HRV2 multiplication in more detail, we investigated the effect of Q7G on the infection cycle of HRV2 through time-of-addition study, reverse transcription-polymerase chain reaction analysis, and effects of Q7G on the infectivity of HRV2 particles. Q7G potently showed anti-HRV2 activity by reducing the formation of a visible CPE. Q7G also inhibited virus replication in the initial stage of virus infection by indirect interaction with virus particles, and ribavirin had a relative weaker efficacy compared to Q7G. Therefore, these data suggest that Q7G exerted its anti-HRV2 effect via the inhibition of virus replication in the early stage and these findings provide important information for the utilization of Q7G for HRV2 treatment.