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.
