Antitrypanosomal and Cytotoxic Activities of 22-Hydroxyclerosterol, a New Sterol from Allexis cauliflora (Violaceae)

In the search for new antiparasitic natural compounds from the medicinal plants from Cameroon, the new 22-hydroxyclerosterol, established as such on the basis of detailed chemical and spectroscopic analysis, was isolated from the hexane extract of the stem bark of Allexis cauliflora together with the known clerosterol. 22-Hydroxyclerosterol inhibited the growth of Trypanosoma brucei brucei cells with an ED(50) value of 1.56 μM. The compound was also established as an uncompetitive inhibitor of the glycolytic enzyme PGI of T. brucei (Ki’= 3 ± 1 μM), an uncompetitive inhibitor of mammalian rabbit muscles’ enzyme PyK (Ki’= 26 ± 3 μM) and a mixed inhibitor of PyK of Leishmania mexicana (Ki’= 65 ± 10 μM; Ki= 24 ± 5 μM).