Chemical composition and toxicity of Jatropha curcas seed oil against Sitophilus zeamais Motschulsky as affected by pre-extraction treatment of seeds

This study evaluated the chemical composition and toxicity of fixed oils obtained from Jatropha curcas seeds pretreated with different methods (cooking, roasting and raw) against maize weevil, Sitophilus zeamais Motschulsky. Palmitic acid was the predominant compound, being 86.60, 69.98 and 54.04%, in oil obtained from cooked, raw and roasted seeds, respectively. Glycerol 1-palmitate was identified in all oil samples (13.40. 16.43 and 27.06% for the oil extracted from cooked, raw and roasted seeds, respectively). Other compounds identified in oils obtained from raw seeds and roasted seeds were palmitoleic acid (2.36 and 2.16%, respectively), linoleic acid (3.13 and 5.80%, respectively) and 9 Octadecenal, (Z)- (8.10 and 10.94%, respectively). At the exposure of the weevils to 200 mu/L air for 24 h, weevil mortality observed in oil obtained from roasted seeds (84.68%) was significantly (p < 0.05) higher than 40.28 and 47.80% observed in oils obtained from cooked and raw seeds, respectively. In contact toxicity bioassay, application of 1.50 mu/cm(2) for 3 h evoked 47.52, 46.96 and 47.36% mortality for oil obtained from roasted, cooked and raw seeds, respectively; being higher than the values observed in untreated control and n-hexane. According to these results, pre-extraction seed treatment affected the chemical composition and toxicity of the oil against Sitophilus zeamais.