THE SYNTHESIS, CHARACTERIZATION AND BIOLOGICAL STUDIES OF N-METHYLINDOLE-3-THIOACETIC ACID

Abstract

The need for the development of new compounds to combat weed resistance to herbicides and microbial resistance to drugs has led to this research. The research aimed at synthesizing N-methylindole-3-thioacetic acid and studying its biological activities. N-methylindole-3-isothiouronium iodide (compound A) was synthesized in a two step but one pot reaction, by reacting N-methyl indole with potassium iodide/iodine mixture followed by addition of thiourea. Its yield was 86.10% and melted with decomposition at 202 – 204oC. In another two-step-one-pot reaction, N-methylindole-3-thioacetic acid (compound B) was synthesized. N-methylindole-3-isothiouronium iodide was hydrolyzed in 10% sodium hydroxide solution to N-methylindole-3-thiol (not isolated) in a hydrogen atmosphere;monochloroacetic acid was coupled with it to give N-methylindole-3-thioacetic acid as a yellowish violet crystal. Its yield and melting point were 95% and 98oC respectively. The structures of the two compounds were ascertained by Fourier transform infra-red spectrophotometer, nuclear magnetic resonance (1D and 2D) and electro-spray ionization mass spectrometer.Both compounds were screened for antimicrobial activities at 10 mg/L. The results obtained revealed that both compounds were potent against test bacteria and fungi. Herbicidal bioassay was carried out with Compound B at various concentrations (2.5, 2.0, 1.0, 1.5 and 0.5 mg/L) against the test weeds (Eleusineindica, Sporoboluspyramidalis, Tridaxprocumbens, and Ageratum conyzoides) for five weeks, using 2,4-D as standard. Results obtained revealed that compound B exhibited no herbicidal activity. However, the observation suggested that the compound might have plant growth regulating activity but further work would be needed to establish this assertion.