Identification of natural compounds with antiviral activities against SARS-associated coronavirus

Li, Shi-you; Chen, Cong; Zhang, Hai-qing; Guo, Hai-yan; Wang, Hui; Wang, Lin; Zhang, Xiang; Hua, Shi-neng; Yu, Jun; Xiao, Pei-gen; Li, Rong-song; Tan, Xuehai

More than 200 Chinese medicinal herb extracts were screened for antiviral activities against Severe Acute Respiratory Syndrome-associated coronavirus (SARS-CoV) using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt (MTS) assay for virus-induced cytopathic effect (CPE). Four of these extracts showed moderate to potent antiviral activities against SARS-CoV with 50% effective concentration (EC(50)) ranging from 2.4 ± 0.2 to 88.2 ± 7.7 μg/ml. Out of the four, Lycoris radiata was most potent. To identify the active component, L. radiata extract was subjected to further fractionation, purification, and CPE/MTS assays. This process led to the identification of a single substance lycorine as an anti-SARS-CoV component with an EC(50) value of 15.7 ± 1.2 nM. This compound has a CC(50) value of 14980.0 ± 912.0 nM in cytotoxicity assay and a selective index (SI) greater than 900. The results suggested that four herbal extracts and the compound lycorine are candidates for the development of new anti-SARS-CoV drugs in the treatment of SARS.