Chemical Constituents and Larvicidal Properties of n-Hexane Extract of Parinari excelsa Seeds

Abstract

The study was conducted to investigate the chemical compositions and larvicidal effect of n-hexane extract of Parinari excelsa seeds against fourth instar larvae of Culex mosquito after 24 h and 48 h exposure. The chemical composition of n-hexane extract of P. excelsa seeds were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS). Larvicidal activity was performed following standard procedures of World Health Organization (WHO). GC-MS analysis showed that the seed extract of P. excelsa contained hexadecyl phenyl carbonate with highest percentage (7.502%, RT=26.39), followed by tetradecyl phenyl carbonate (5.77%, RT=25.90), 1-methyl cyclohex-3-enyldodecyl fumarate (5.70%, RT=24.58), decyl phenyl carbonate (4.70%, RT=28.64) and the lowest, octadecyl-2,2,2-trichloroethyl carbonate (0.62%, RT=13.71). The result showed significant (p<0.05) mortality of larvae  in 24 h and 48 h of exposure. However, the highest larval mortality  was recorded at 48 h exposure. Result of regression analysis indicated that mortality rate positively correlated with concentration having a regression coefficient (R) close to one in each exposure case. The estimated lethal concentrations (LC50) for 24 h and 48 h exposure were 2.056±0.176 µg/ml and 0.429±0.150 µg/ml respectively. This indicates that larvicidal activity recorded for 48 h exposure was 4.8 times more than that recorded for 24 h exposure. The study demonstrated that n-hexane extract of P. excelsa seeds exhibited larvicidal potential and can be utilized as biopesticides to minimize the multiplication of mosquitoes that transmit vector borne diseases.