Abstract

COMPARATIVE EVALUATION OF LARVICIDAL PROPERTIES OF METHANOL EXTRACTS AND FRACTIONS OF MYRISTICA FRAGRANS SEED HOUTT (MYRISTICACEAE) AND THYMUS VULGARIS LEAF LINN (LAMIACEAE) ON THE FOURTH INSTAR LARVAE OF CULEX QUINQUEFASCIATUS LINN AND THE CONTROL OF FIL

Umoh Romanus A.*, Johnny Imoh Imeh, Offor Samuel J., Effiong Daniel E. and Ezeh Uchechukwu A.

Abstract

Introduction: Larvicides are generally chemical substances used to kill mosquitoes when in their larval stage, this is done by exhibiting certain acute toxic effects thus preventing its further progression to pupa and adult stages, thereby preventing the spread of diseases caused by mosquitoes. Aim: The aim of this work is to compare the larvicidal properties of methanol extracts and solvent partitioned fractions of Myristica fragrans HOUTT. seeds and Thymus Vulgaris Linn. leaves on the fourth instar larvae of Culex quinquefasciatus vector of filariasis. Materials & Methods: The Myristica fragrans seeds were obtained, crushed into coarse powder and defatted in n-hexane for 24 hours and air-dried. The defatted seeds and leaves powders were separately marcerated in 100% redistilled methanol for 72 hours. The percentage yields were obtained and the toxicity evaluation was done by exposing the fourth instar larvae of Culex quinquefasciatus to varying concentrations of reconstituted methanol crude extracts and solvent partitioned fractions of M.fragrans seeds and T. Vulgaris leaves. The larval mortalities were determined using the non-linear regression analysis of a statistical package graph pad prism®. Results: The results of the LC50 of the methanol crude extracts of M. fragrans was 0.23mg/mL while that of the T. Vulgaris was 0.64mg/mL. The LC50 of the fraction of M. fragrans for n-hexane was 0.01mg/mL and 0.37mg/mL for Chloroform fraction respectively, while T.vulgaris had LC50 of 0.18mg/mL of n-hexane fraction and 0.55mg/mL for chloroform fraction, compared to that of nicotine with LC50 of 0.01mg/mL. Moreover, the larvicidal effects of the ethyl acetate and that of aqueous fractions were not feasible. Conclusion: The methanol crude extracts, n-hexane and chloroform fractions of M. fragrans considering differences in their percentage mortalities and LC50 had the highest larvicidal activity than T. vulgaris, but n-hexane fractions of M. fragrans and T. vulgaris offer great potentials in the vector control of culex mosquitoes that cause filariasis, even though n-hexane fraction of M. fragrans has a higher activity than T. vulgaris of n-hexane fraction comparing their LC50 of 0 01 mg/mL and 0.18mg/mL respectively and 0.01 mg/mL of the positive control, the nicotine.

Keywords: Myristica fragrans, Thymus vulgaris, Filariasis, Larvicides, Toxicity, Mortality, Culex quinquefasciatus and Nicotine.