Anti-respiratory syncytial virus activities of leaf extracts of Alchornea cordifolia and Alchornea floribunda

Respiratory syncytial virus (RSV) causes viral infection of a global proportion. Currently, there is no approved vaccine or useful antiviral drug against it. Natural products hold potential for discovery of anti-RSV agents. The present study assessed the anti-RSV activities of Alchornea cordifolia (AC) (Shumach. and Thonn.) Mϋll. Arg. and Alchornea floribunda (AF) Mϋll. Arg., Antiviral activities of AC and AF leaf extracts were evaluated by a modified viral plaque reduction assay. Parallel assays for effect of the antiviral agents on cell viabilities were carried out the cells using the 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) reduction assays. Mechanism of anti-RSV action of the extracts was done based on time-of-addition assay. Extracts of AC and AF, showed anti-RSV activities with IC50 = 5.64 ± 1.16, and 75.62 ± 3.38 µg/ml, respectively while the cell cytotoxic effect of extracts were TC50 = 103.14 ± 3.98, and 333.82 ± 6.32 µg/ml, respectively. Time-of-addition assay results suggested that AC and AF interfere with viral replication at a viral post-entry step. The extracts of AC and AF exhibited profound anti-RSV activities warranting their development for further possible clinical utility against RSV. Key words: Alchornea cordifolia, Alchornea floribunda, respiratory syncytial virus (RSV), antiviral, time-of-addition, cell culture.