Effective Antimalarial Activities of α-Hydroxy Diynes Isolated from Ongokea gore

Three diynes, octadec-17-ene-9,11-diynoate ethyl (1: ), 8-hydroxy-octadeca-13,17-diene-9,11-diynoate ethyl (2: ), and 8-hydroxy-octadec-13-ene-9,11-diynoate ethyl (3: ), were isolated from Ongokea gore seed oil. The structure assignment of these three compounds was based according to chemical and spectroscopic data. They were screened against Plasmodium falciparum, the parasite that causes malaria. In vitro micro-test (Mark III, supported by the World Health Organization) was developed to assess the response of P. falciparum to the isolated three compounds, and statistical analysis were performed for determination of the concentration that inhibits 50% of the parasite maturation (IC₅₀). Two of the three diynes (2: and 3: ) showed a very effective in vitro antimalarial activity with an IC₅₀ of 4.5 and 1.7 µM, respectively. Compound 3: exhibited better activity than quinine (IC₅₀ 1.9 µM), the drug reference, while compound 1: had no antimalarial activity (IC₅₀ > 125 µM). In the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cytotoxicity screening, all compounds showed no toxicity (mean IC₅₀ of 90 µM for each compound).