4-Methoxycinnamaldehyde inhibited human respiratory syncytial virus in a human larynx carcinoma cell line

4-Methoxycinnamaldehyde, an active constituent of Agastache rugosa, was examined for its cytoprotective activity against RSV by XT-F method in human larynx carcinoma cell line. 4-Methoxycinnamaldehyde could effectively inhibit cytopathic effect of RSV (p < 0.0001) with an estimated IC50 of 0.055 mu g/ml and a selectivity index (SI) of 898.2. 4-Methoxycinnamaidehyde (0.03 mu g/ml) could inhibit viral entrance by interfering viral attachment (IC50 of 0.06 mu g/ml; p < 0.0001) and internalization (IC50 of 0.01 mu g/ml; p < 0.0001). 4-Methoxycinnamaldehyde significantly increased the basal production of IFN (p = 0.0015), but not the virus-induced IFN production. Therefore, its cytoprotective activity against RSV was not mediated by interferon. In conclusion, 4-methoxycinnamaldehyde might be helpful to manage the disease induced by RSV infection. (c) 2009 Elsevier GmbH. All rights reserved.