Synthesis, in-vitro antiprotozoal activity and molecular docking study of isothiocyanate derivatives

Novel isothiocyanate derivatives were synthesized starting from noscapine, bile acids, amino acids, and some aromatic compounds. Antiparasitic activities of the synthesized derivatives were tested against four unicellular protozoa, i.e., Trypanosoma brucei rhodesiense, T. cruzi, Leishmania donovani, and Plasmodium falciparum. Interestingly, seven isothiocyanate analogues displayed promising antiparasitic activity against Leishmania donovani with IC50 values between 0.4 and 1.0microM and selectivity index (SI) ranged from 7.8 to 18.4, comparable to the standard drug miltefosine (IC50=0.7muM). Compound 7h demonstrated the best antileishmanial activity with an IC50 value of 0.4microM. Seven products exhibited inhibition activity against T. brucei rhodesiense with IC50s below 2.0muM and SI between 2.7 and 29.3. Four primary amine derivatives of noscapine and five isothiocyanate derivatives exhibited antiplasmodial activity with IC50s in the range of 1.1-2.7microM and SI values between 1.1 and 14.5. The isothiocyanate derivative 7c showed against T. cruzi with an IC50 value of 1.9microM and SI 4. Molecular docking and ADMET studies were performed to investigate the interaction between active ligands and T. brucei trypanothione reductase active site. The docking studies showed significant binding affinity of noscapine derivatives to enzyme active site and good compatibility with experimental data.