In vitro Anti-Herpes simplex Type-1 Virus Evaluation of Extracts from Kenya Grown Pyrethrum (Chrysanthemum cinerariaefolium)

Objective: To evaluate in vitro anti-Herpes simplex type 1 activity of methanol and aqueous crude extracts of pyrethrum (Chrysanthemum cinerariaefolium) plant grown in Kenya.

Methods: Cytotoxic effect of methanol and aqueous extracts was determined on vero cells (African green monkey kidney cells) by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-DiphenylTetrazolium Bromide) reduction colorimetric assay. Antiviral effect of pyrethrum extracts was evaluated; before (post-treatment infection) virus infection to the cells and after (pre-treatment infection) virus infection to cells.

Results: Methanol extract exhibited higher cytotoxicity of CC50 = 42.23 ± 0.320 µg/ml compared to aqueous extract of CC50 = 249 ± 8.4 µg/ml. Methanol extract exhibited a higher anti HSV-1 potency of IC50 = 1.69 µg/ml (TI = 24.99) than the aqueous extract of IC50 = 38.13 µg/ml (TI = 6.53) in the post-treatment infection evaluations. This might be due to its effect on cellular receptors preventing virus entry, while the aqueous extract exhibited higher virus inhibitory potency in the pre-treatment infection, of IC50 = 23.21 µg/ml (TI=10.73) compared to the methanol extract of IC50 = 11.18 µg/ml (TI =3.78), this effect could be due to its effect on some stage during HSV virus replication process.

Conclusions: Crude methanol and aqueous extracts from Kenyan grown pyrethrum exhibited inhibition potency against HSV-1 in vitro on Vero cells.