Ocimum tenuiflorum possesses antiviral activity against bovine herpes virus–1

The antiviral activity of seed and leaf extracts of Ocimum tenuiflorum against Bovine herpes virus-1 (BHV-1) was studied in vitro. MDBK cells (5 x 10⁵), non-cytotoxic concentration of the each extracts and 10–1000 TCID virus was added in quadruplicate wells of a 96 well tissue culture plate. Mock infected 50 cells served as the negative control. Protective efficacy of the extracts was measured by decrease in the extent of cell degeneration caused by the virus as measured by lactate dehydrogenase activity in the cell culture supernatant and concomitant increase in the cell viability as quantified by mitochondrial dehydrogenase activity (MTT reduction assay). Non-toxic concentration of aqueous (37.90 μg/ml) and alcoholic (9.45 μg/ml) extract of dried leaves, aqueous (11.25 μg/ml) and boiled aqueous (12.50 μg/ml) extract of fresh leaves, decoction of fresh leaves (16.65 μg/ml) and aqueous extract of seeds (16.65 μg/ml) was found to inhibit virus multiplication in cells. When the MDBK cell monolayer pre-treated with the extracts for 4 h at 37°C was infected with BHV-1, significant protection of the cells was observed. However, the extracts were not effective when added at post-adsorption stage of virus infection indicating that O. tenuiflorum inhibits early stage of the virus multiplication. Antiviral component(s) present in the extract(s) appears to be polar and heat stable.