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

Abstract

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 <i>Ongokea gore</i> seed oil. The structure assignment of these three compounds was based according to chemical and spectroscopic data. They were screened against <i>Plasmodium falciparum</i>, the parasite that causes malaria. <i>In vitro</i> micro-test (Mark III, supported by the World Health Organization) was developed to assess the response of <i>P. falciparum</i> 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 <i>in vitro</i> 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).