PHYTOCHEMICAL INVESTIGATION AND INSECTICIDAL FORMULATION BASED ON ESSENTIAL OIL FROM OCIMUM BASILICUM LINN (SWEET BASIL) HERB SUPPORTED ONTO MODIFIED KAOLINITE AGAINST SITOPHILUS ZEAMAIS

Abstract

The Ocimum basilicum Linn (Lamiaceae) leaves extract was investigated for its phytochemical constituents and its essential oil was formulated using modified and unmodified kaolinite clay as supporting material. To this effect, the petroleum ether, chloroform/methanol (1:1) and the methanol crude extracts were subjected to qualitative phytochemical screening and the results of the screening test revealed that it is rich in many secondary and primary metabolites such as flavonoids, terpernoids, glycosides, alkaloids and phenols. Two compounds namely hexan2-ylbenzene and (2E, 6E)-10-ethylhexadeca-2,6-dien-yl acetate were isolated using PTLC and the structures of these compounds were identified using FT-IR and NMR techniques (1HNMR, 13C-NMR and DEPT-135). Essential oil was also extracted by hydrodistilation from the O. basilicum leaves and it was investigated by GC-MS. 9-octadecenoic acid (z), methyl ester (25.12%), hexadecanoic acid, methyl ester (19.26), trans-iso eugenol (13.12) and eucalyptol (11.19) were the first four major constituents of the plant leaves of the essential oil. The modified and unmodified kaolinite clay was characterized by SEM/EDX, TGA, FT-IR and XRD techniques. XRD and mineralogical constituents of the clay material was confirmed to be kaolinite. The unformulated essential oil and the methanol extracts were tested for insecticidal activities on the Sitophilus zeamais and the result revealed that the essential oil was more active with in 24 h of exposure time. The effect of exposure time, the formulation efficacy, the stability and the remnant effect of the formulated essential oil were tested and the result showed an improvement for insecticidal activities of the maize weevil for a long period of time with high persistence. The antitubercular activities of the extracts were also assessed and have shown promising activities against the M. tuberculosis H37Rv strain with good MIC values. Based on the observed result, emphases have to be made on the insecticidal and antitubercular activities of the plant, Ocimum basilicum by formulating the essential oil.