Assessment of the Larvicidal potentials of Thymol derivatives on Anopheles mosquitoes

Thymol (1) a major constituent of the South Eastern Nigeria variety of ocimum gratissimum popularly known as nchawu (scent leaf) was converted to its O-methyl (2), O-ethyl (3), acetate (4) and the Benzyloxy (5) derivatives that are characterized by their spectral data such as infra red, proton n.m.r. and mass spectra. Tests on their insecticidal potency show that, like the parent compound thymol (1), they also possess insecticidal properties in decreasing order Benzyloxy > Acetate > O-ethyl > O-methyl. This order is explained partly by the electron withdrawing tendency of the benzyloxy and acetate groups and also that, as the molecular weight of the derivatives increases the solubility decreases.