The aqueous extracts of three medicinal plants, Carissa edulis
(Forssk.) Vahl (Apocynaceae), Prunus africana (Hook.f.) Kalkm
(Rosaceae) and Melia azedarach L. (Meliaceae) have shown significant
reduction in the replication of human cytomegalovirus (HCMV) in human
embryonic lung (HEL) fibroblasts cells in vitro. Using the plaque
inhibition assay for the determination of anti-viral activity, the HEL
fibroblast cells cultured in 24 well plates were infected with 1 x 102
PFU 91S HCMV and treated with various concentrations of the extracts.
The plaques formed were counted after 7 days incubation at 37\ub0C in
5% CO2 and the percent plaques inhibited were calculated against
infected untreated control. The effective concentrations inhibiting
plaque formation by 50% (EC50) was found between 40 to 80 \u3bcg/ml
for all the extracts. The cell cytotoxic concentrations (CC50) for each
of the three extracts, by the trypan blue exclusion test, gave a safe
therapeutic index. These results have demonstrated the potential
anti-viral activities of the extracts of the three medicinal plants at
non-cytotoxic concentrations