Eucalyptus robusta leaves extract exerts antiviral activity by inhibiting viral entry, replication and budding

Eucalyptus is used against skin ailments in Ayurvedic medicine, however, its efficacy against dermatotropic viruses is unknown. The present study reported the antiviral efficacy of E. robusta leaves methanolic extract against buffalo pox-virus (BPXV). Phytochemical analysis of the test extract was performed by GC-MS. The antiviral efficacy of the extract was assessed by cytotoxicity assay, attachment assay, virus entry assay, and budding assay using the Vero cell line. Further, viral DNA was quantified using the qPCR technique. Eucalyptol was found to be the major biomolecule in phytochemical analysis. Other phytoconstituents identified were b-pinene, borneol, alpha phellandrene, ocatdec-9-enoic acid, vaccenic acids, etc. Significant inhibition of BPXV was achieved at 10 mu g/ml (non-cytotoxic concentration), however, the virucidal action was not produced even at 100 mu g/ ml. Virus attachment assay as well as a relative number of viral DNA copies did not differ significantly between extract-treated and vehicletreated groups. Albeit, data mined from viral yield was found to be significantly reduced following treatment with extract in viral entry assay. Application of extract at 36 hours post-infection (hpi) reduced almost 70 % of viral titer. Based on the above findings, it may be conferred that the herbal test extract showed potential activity against dermatotropic virus (BPVX), especially through targeting viral entry and budding. Thus, Eucalyptus robusta leaf extract may be bio-prospected as a naive congener against such viruses.