Secochiliolide ester derivatives: Preparation and evaluation of their antitrypanosomal and antimalarial efficacy

In the present study, a series of new esters of secochiliolide acid (SA), a diterpene isolated from Nardophyllum bryoides, were synthesized in good yield. All compounds were evaluated for their in vitro antiparasitic properties (on Plasmodium falciparum and Trypanosoma brucei brucei) and cytotoxicity (on WI38, normal mammalian cells). They displayed moderate antitrypanosomal activity with IC50 values between 2.55 and 18.14 μm, with selectivity indices >10, and low antiplasmodial effects with IC50  > 29 μm. The only exception was the n-hexyl ester of SA, which showed a strong and selective antiplasmodial activity (IC50  = 1.99 μm and selectivity index = 117.0). The in vivo antimalarial efficacy of this compound was then assessed according to the 4-day suppressive test of Peters in mice. An intraperitoneal treatment at 50 mg kg-1  day-1 induced a slight parasitaemia reduction by 56% which was statistically significant on day 4 post-infection and an increase in the survival time.