Phytoconstituents and Insecticidal Activity of Different Solvent Leaf Extracts of Chromolaena odorata L., against Sitophilus zeamais (Coleoptera: Curculionidae)

The chemical profiles of volatile compounds obtained from different leaf extracts of Chromolaena odorata L, were determined by gas chromatography (GC) and gas chromatography couples with mass spectrometry (GC/MS). The hexane extract was characterized by abundance of phytol (23.1%), caryophyllene oxide (12.7%), germacrene D (9.0%) and (7.8%) and β-caryophyllene (8.2%). The major constituents of the chloroform extract were dodecyl acetate (13.6%), oleic acid methyl ester (11.2%), di-n-octyl phthalate (11.1%) and hexadecanoic acid methyl ester (6.6%). Phytol (11.1%), caryophyllene oxide (9.9%), g-muurolene (6.4%) and hexadecanoic acid (5.4%) were the main compounds of the ethyl acetate fraction. The main components of the methanol extract were hexadecanoic acid (11.2%), caryophyllene oxide (8.5%), α-terpineol (7.8%) and α-cubebene (7.7%). Overall, ubiquitous terpenes are less common when compared with previous investigation. However, fatty acids, aromatic compounds and diterpenoids contributed significantly to the major volatile fractions. The insecticidal sensitivity of different solvent leaf extracts of C. odorata towards the adults of S. zeamais after 96h exposure was found in the order: methanol > ethyl acetate > chloroform > hexane.

Aims: The aim of this research work was to investigate the chemical constituents of the volatile oils from different solvent extracts of Chromolaena odorara and evaluation of their insecticidal properties.

Study Design: Extraction of C. odorata with different solvents by Soxhlet apparatus and the insecticidal property.

Place and Duration of Study: Fresh leaves of C. odorata were collected from Mowe-Ofada, Obafemi-Owode Local Government Area, Ogun State, Nigeria.

Methodology: Air-dried and pulverized leaves were extracted with hexane, methanol, chloroform and ethyl acetate and their chemical constituents were analyzed by GC and GC/MS. The oils were then evaluated for their insecticidal activity.

Results: A total of sixty-seven compounds were identified, amounting to 96.4%, 91.2%, 91.1% and 93.4% of the total constituents of hexane, chloroform, ethyl acetate and methanol fraction, respectively. The major were compounds phytol, caryophyllene oxide, dodecyl acetate, oleic acid, hexadecanoic acid, di-n-octyl phthalate. The insecticidal sensitivity of different solvent extracts of C. odorata towards the adults of S. zeamais depicts its potential as an insecticide.

Conclusion: The chemical composition of the volatile compounds differed from each other and the extracts displayed potent insecticidal activities.