Evaluation of the antimicrobial and larvicidal activities of n-hexane root extract of Ixoria coccinea L. (Rubiaceae)

The antimicrobial as well as the larvicidal activities of n-hexane root extract of Ixoria coccinea against Aedes aegypti was evaluated in this work. The extraction was done using maceration method. Agar well diffusion method was used to assess the antimicrobial activity of the extract against different clinical isolates of gram positive and gram-negative bacteria. The larvicidal activity was evaluated according to World Health Organization (WHO) guideline for larvicidal assay as follow: a stock solution of 10mg/ml was prepared for each extract from which five different concentrations (1.0, 2.0, 3.0, 4.0 and 5mg/ml in 100ml) were made and used for the test. A control was also prepared for each extract. A total of 20 larvae were used for each of the concentration and mortality was recorded at 24, 48 and 72 hours. The result of the antimicrobial assay showed that at 100mg/ml concentration, the extract gave an inhibition zone diameter of 17±1.41mm for Staphylococcus aureus, 8±0.82mm for Bacillus spp, 2±0.00mm for Stapylococcus epidermidis, 4±0.58mm for Pseudomonas aeruginosa and 6±1.29mm for Escherichia coli. The extract was most active against Staphylococcus aureus with an MIC of 50mg/ml. The extract is not active against all the fungi species used in the test. Examination of the result for larvicidal assay against Aedes aegypti larvae showed that the LC50 after 24, 48 and 72 hours are 1.782, 1.376 and 0.686mg/ml respectively. At concentration of 3mg/ml there was 100% mortality after 72 hours. The results showed that the n-hexane root could serve as a source of both antibiotic and mosquito larvicides