Tatanan A from the Acorus calamus L. root inhibited dengue virus proliferation and infections

Background: Acorus calamus 1. (Acoraceae) is a well-known traditional Chinese medicinal plant, whose root are historically mainly used to treat neurodegenerative diseases, and for cholera treatment. This datum strongly indicates the antimicrobial activity of A. calamus. Purpose: Our goal is to find the active constituents of A. calamus to treat dengue virus (DENV) infections, and to study the effects and mechanisms of these active substances. Methods: The root of A. calamus was extracted by ethanol. Mosquito larva C6/36 cells were used for DENV2 replication and transfection host. Mouse kidney fibroblast cells (BHK-21) were used as a host cell to study the infection ability of the virus. DENV2-induced cytopathic effect (CPE) and plaque assay were used to evaluate the inhibitory effect of A. calamus extracts on DENV2 infectivity inhibition. The levels of E and NS1 protein expression were measured by real-time PCR and western blot assays. Results: 12 compounds were isolated from ethanol extract of A. calamus root, tatanan A showed the best anti-DENV ability among these 12 compounds, which significantly alleviated DENV2-induced CPE and cytotoxicity effects, with an EC50 of 3.9 mu M. In addition, RNA replication assay further confirmed the antivirus ability of tatanan A. Time-addition assay showed that tatanan A affected the early stage of viral RNA replication, which in turn inhibited mRNA and protein levels of DENV2. Conclusions: These results demonstrated the anti-DENV2 effect of tatanan A, in inhibiting DENV2 RNA replication and infections. In summary, tatanan A was found to be a novel natural DENV inhibitor and a potential candidate for the treatment of DENV infectious disease.