The antiviral activity of compounds isolated from Kenyan Carissa edulis (Forssk.) Vahl

Abstract

Extracts of a Kenyan medicinal plant, Carissa edulis (Forssk.) Vahl, were subjected to bioactivity guided phytochemical analysis for identification of biological makers of activity. Pure compounds; lupeol, oleuropein, carissol and β-amyrin were subsequently isolated. In vitro evaluations of the compounds against viral strains of Herpes simples virus types 1 revealed a significant activity for lupeolat EC50 of between 2.98 - 4.2 µg/ml for both sensitive and resistant strains with a high therapeutic index (TI > 38). A concentration of the compound at 10.0 µg/ml was virucidal, reducing viral yields in Vero E6 cells by 98.3%. On oral administration to mice at 20.0 µg/ml following a cutaneous viral infection, a delayed onset of infections of slow progression to mild and sever zosteriform lesions were observed (p £ 0.05 test Vs control by repeated measures ANOVA). The mice receiving treatment with the compound also exhibited increased mean survival times as opposed to control (p ≤ 0.05 test verses control by Student’s t-test) with a therapeutic index >5 (LD50 >100.0 µg/ml). The results indicate promising antiviral activity of lupeol and necessitate further examinations of efficacy and safety in higher mammals.   Key words: Antiviral activity, lupeol, Carissa edulis, Herpes simplex virus.