Project Materials

LARVICIDAL POTENTIAL OF EXTRACTS OF Persea Americana SEED AND Chromolaena odorata LEAF AGAINST Aedes vittatus MOSQUITO

ABSTRACT

The larvicidal activity of different solvent extracts (ethanol, ethyl acetate, and n-hexane) of Persea americana seed and Chromolaena odorata leaves against the Aedes vittatus mosquito was investigated. The most potent solvent (n-hexane) extracts of both plants were fractionated using column chromatography, and the most effective fractions were separated and identified using Gas Chromatography Mass Spectrometry and Fourier Transform Infrared methods. Phytochemical analysis confirmed the presence of steroids, cardiac glycosides, and terpenoids in all extracts. The larvicidal bioassay of Persea americana seed yielded LC50 values of 0.827ppm, 1.799ppm, and 2.732ppm for n-hexane, ethanol, and ethyl acetate extracts, respectively, while Chromolaena odorata leaf extract yielded LC50 values of 1.835ppm, 3.314ppm, and 5.163ppm for n-hexane, ethanol, and ethyl acetate. Column chromatography fractionation of the most powerful n-hexane (crude) extracts of both plants revealed enhanced activity in some of the fractions of Persea americana (nHPa6) and Chromolaena odorata (nHCo6) that demonstrated higher mortality, with LC50 values of 0.486ppm and 1.308ppm, respectively. GC/MS analysis of nHPa6 and nHCo6 components revealed that oleic acid was the most prevalent in both plant fractions. The FTIR analysis of nHPa6 and nHCo6 revealed absorption bands for the functional groups present, which included alcohol, alkane, alkene, alkyl halide, aldehyde, carboxylic acid, and carbonyl ester, so validating the GCMS result. The n-hexane, ethanol, and ethyl acetate extracts of P. americana seed and C. odorata leaves shown good larvicidal action and should thus be further investigated for mosquito larvae control.

Chapter one

INTRODUCTION

Insect-borne diseases continue to cause significant morbidity and mortality worldwide. Mosquito species from the genera Anopheles, Aedes, and Culex are vectors (Redwane et al., 2002) for the transmission of malaria, dengue fever, yellow fever, filariasis, schistosomiasis, and Japanese encephalitis (JE), infecting over 700 million people each year (Oyewole et al., 2010; Govindarajan, 2009).

Mosquitoes can produce allergic reactions in people, including local skin irritation and systemic reactions like angioedema. Aedes spp. are widely recognised as the vectors responsible for the transmission of yellow fever and dengue fever, which are indigenous to Southeast Asia, the Pacific island region, Africa, Central and South America.

The World Health Organisation (W.H.O. 2012) has identified vector control as a critical component of the global strategy for preventing insect-borne diseases.

Chemical-based insecticides are the most generally used strategy for controlling mosquito-borne diseases, but they are not without drawbacks, including human and environmental toxicity, resistance, affordability, and availability (Ghoshet al., 2012).

Plant extracts have proven to be effective mosquito egg and larvae control agents because they include a large number of bioactive components that are easily biodegradable into nontoxic products. Many studies have shown that plant extracts or essential oils are effective against mosquito larvae.

They function as larvicides, insect development regulators, repellents, and oviposition attractants (Pushpanathan, 2008; Samidurai et al., 2009; Mathivanant et al., 2010).

Persea Americana is an evergreen tree of the Lauraceae family, and its fruits are commonly known as avocado pear or alligator pear. The plant originated in Central America, but it has easily adapted to various tropical locations, making it commonly farmed in tropical and subtropical areas.

The various parts of this plant (leaves, fruits, and seed) have numerous applications, ranging from edible pulp as a source of nutrients to seed preparation as a treatment (Arukwe et al., 2012).