Dur Han Kwon

Inhibitory effects of quercetin 3-rhamnoside on influenza A virus replication

Influenza viruses cause significant morbidity and mortality in humans through epidemics or pandemics. The lack of effective therapeutical treatment underlines the importance of research for new antiviral compounds. Flavonoids widely exist in the plant kingdom, and their antiviral activities against various viruses have been recently reported. In this study, the anti-influenza A/WS/33 virus of quercetin 3-rhamnoside (Q3R) from Houttuynia cordata was evaluated using a cytopathic effect (CPE) reduction method, the assay results demonstrated that Q3R possessed strong anti-influenza A/WS/33 virus reducing the formation of a visible CPE. Q3R also did inhibit virus replication in the initial stage of virus infection by indirect interaction with virus particles. However, oseltamivir has relative weaker efficacy compared to Q3R. Therefore, these findings provide important information for the utilization of Q3R for influenza treatment.

Quercetin 3‐rhamnoside Exerts Antiinfluenza A Virus Activity in Mice

Our previous report showed that quercetin 3‐rhamnoside (Q3R) possessed antiviral activity against influenza A/WS/33 virus in vitro. The present study evaluated the effect of Q3R on influenza A/WS/33 virus infected mice. Mice orally treated with Q3R (6.25 mg/kg per dose) at 2 h before and once daily for 6 days after influenza virus infection showed significant decreases in weight loss, and decreased mortality. Lung virus titers of mice killed at 6 days after infection were about 2000 times lower than that of the placebo‐treated control mice and about two times lower than that for the oseltamivir‐treated mice. Furthermore, histological evaluation showed that administration of Q3R delayed the development and progression of pulmonary lesions. Therefore, Q3R could be an attractive lead for the development of antiviral agents against influenza virus. Copyright

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.

Antiviral and anticancer activities of 13(E)‐labd‐13‐ene‐8α,15‐diol isolated from Brachyglottis monroi

The antiviral activity of 13(E)‐labd‐13‐ene‐8α,15‐diol (1), isolated from Brachyglottis monroi, was examined against human rhinovirus 2 (HRV2) and 3 (HRV3), and the anticancer activity on human cancer cells (A549 and Hep2). Compound (1) showed strong anti‐HRV2 and HRV3 activity with a 50% inhibitory concentration (IC50) of 2.68 and 0.87 µg/mL, respectively, and a 50% cytotoxicity concentration (CC50) of 59.45 µg/mL. Ribavirin only showed anti‐HRV3 activity with an IC50 of 30.48 µg/mL and a CC50 > 100 µg/mL. The addition of compound (1) to HRV‐infected HeLa cells directly reduced the formation of visible cytopathic effect (CPE) and it directly interacted with HRV particles. Furthermore, A549 and Hep2 cells incubated with 32 µg/mL of compound (1) for 48 h exhibited antilung and antilaryngeal cancer activities, with a viability of less than 50%. These results suggest that compound (1) may be used as a potential antiviral and anticancer agent. Copyright