Melia azedarach is commonly used in traditional and folk medicine in Korea and China to treat a variety of diseases including diarrheal, diabetic, rheumatic, and hypertensive disease. The aim of this study was to determine the potential prophylactic and therapeutic effects of Melia azedarach against a broad spectrum of viruses in in vitro cell culture model and the protective effect against different influenza A subtypes in BALB/c mice model. An effective dose of pre-treatment, co-treatment, and post-treatment of Melia azedarach significantly reduced the replication of coxsackievirus, herpes simplex virus, influenza A virus, enterovirus, and bovine rhinovirus in both epithelial and macrophage cell lines. Melia azedarach treatment remarkably promoted the phosphorylation of the key molecules associated with the type-1 interferon and NF-κB signaling pathways. Furthermore, it induced the secretion of type-1 interferon and pro-inflammatory cytokines and the subsequent stimulation of the antiviral state in both epithelial and macrophage cells. Interestingly, oral inoculation of an effective dose of herb extract significantly improved viral clearance in the lungs of BALB/c mice, thus exhibiting protection against several subtypes of influenza A virus. Together with our results indicate that an extracts of Melia azedarach and its components could exhibit a potential natural source of an antiviral drug candidate for a broad spectrum of viruses in animal and humans.

Salvia miltiorrhiza (Danshen) is perennial plant and commonly used in traditional Chinese medicine to treat numerous diseases like cardiovascular and cerebrovascular diseases, coronary heart disease, myocardial infarction, stroke and some viral diseases. Nevertheless, no study has been conducted on the antiviral properties of crude extract of Salvia miltiorrhiza against Influenza virus. In an attempt to identify new potential anti-influenza virus agents, 200 natural oriental herbal medicines were screened and we found that Salvia miltiorrhiza has a potential anti-influenza effect. Therefore, in this study, we investigated the protective effect of aqueous extract from Salvia miltiorrhiza against divergent influenza A subtypes using murine model of influenza A infection. Effective dose of aqueous extracts of Salvia miltiorrhiza in BALB/c mice displayed higher survival rate and lower lung viral titers when challenged with lethal doses of influenza A subtypes ({A/Aquatic bird/Korea/ W81/2005(H5N2)}, {A/PR/8/34(H1N1)}, {A/Aquatic bird/Korea/W44/2005(H7N3)} and {A/Chicken/ Korea/116/2004(H9N2)}). In vivo results exhibited that Salvia miltiorrhiza induced prophylactic effect in BALB/c mice against Influenza virus by disrupting viral replication or preventing viral infection by creating an antiviral state in the lungs. Taken together, the use of aqueous extracts of Salvia miltiorrhiza as an orally active antiviral agent, will be potential candidates for prophylactic treatments against Influenza A virus for humans and animals.