In vitro anti-leishmanial activities and structure-activity relationship analysis of new antimony(III) complexes

Abstract

New fourteen antimony(III) complexes of general formula [SbL_nCl₃] (where n= 1 or 2, L =2-aminopyridine, 5-methyl-2-aminopyridine, 2-aminopyrimidine, 4,6-dimethoxy-2-aminopyrimidine, 2-benzyl-2-thiopseudeourea,2-guanidinobenzimidazole, 2-amino-5-thiol-4,6-dimethoxypyrimidine, 2-amino-5-(1H-tetrazol-5-ylthio)-4,6-dimethoxypyrimidine, N-2-pyrimidine, 2-piperidinecarboxamide, N-2-pyrimidine, 2-pyrrolidinecarboxamide, 2-amino-5-(1H-tetrazol-5-iltiyo)-4,6-dimethoxypyrimidine-2-pyrrolidinecarboxamide and N-2-pyrimidine, 5-chloro-2-thiophenecarboxamide, N-2-benzothiazol-2-pyrrolidinecarboxaamide, N,N-(1,2-phenyl)dipyrrolidine-2-carboxamide) have been synthesized and their anti-leishmanial activity have been assessed in vitro against Leishmania tropica promastigotes. The best complex, Sb(2-guanidinobenzimidazole)Cl₃ is demostrated 3.16% growth inhibition at a concentration of 31.25 μg/mL. In general, antimony(III) complexes containing pyrimidine ligands has showed higher anti-leishmanial activity than antimony(III) complexes bearing pyridine ligands, and electron-donating substituents decrease the anti-leishmanial activity. All complexes have been optimised with DFT/B3LYP/LANL2DZ method in the gas phase. Several descriptors are tested to find a quantitative correlation between anti-leishmanial activity and structural properties of the complexes by best multiple linear regression method. Good correlations are obtained with minimum net atomic charge for a C atom and maximum bond order of a Cl atom. The developed QSAR equation is internally validated.