Benzimidazole Schiff base derivatives: synthesis, characterization and antimicrobial activity.

A series of Schiff bases (-) bearing benzimidazole moiety was successfully synthesized in ethanol by refluxing Oct-2-ynoic acid (1,3-dihydrobenzimidazole-2-ylidene)amide with substituted amines. Fourier transform infrared (FTIR), ultra violet light (UV-VIS), elemental analysis, proton (H) and carbon (C) nuclear magnetic resonance spectroscopy were used to characterize the newly synthesized Schiff bases. Micro dilution method was used to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of the Schiff bases, against 14 human pathogenic bacteria (8 Gram negative and 6 Gram positive) and against 7 fungal strains (5 and 2 ) representatives. Antimalarial activity against and antitrypanosomal property against was studied in vitro at a single dose concentration of the Schiff bases. Cytotoxicity of the Schiff bases was assessed against human cervix adenocarcinoma (HeLa) cells. Results obtained show that the newly synthesized Schiff bases are very potent antimicrobial agents. Gram negative bacteria and were more affected on exposure to Compounds - (MIC 7.8 µg/mL) which in turn exhibited more antibacterial potency than nalidixic acid reference drug that displayed MICs between 64 and 512 µg/mL against and respectively. The test compounds also demonstrated high cytotoxic effect against and as they displayed MFC 7.8 and 15.6 µg/mL. Compound exhibited the highest fungicidal property from this series with MFC alternating between 7.8 and 15.6 µg/mL against the investigated strains. The malarial activity revealed Compounds and as the more potent antiplasmodial compounds in this group exhibiting 95% and 85% growth inhibition respectively. The IC of Compounds and were determined and found to be IC 26.96 and 28.31 µg/mL respectively. Compound was the most cytotoxic agent against HeLa cells in this group with 48% cell growth inhibition. Compounds , and were biocompatible with HeLa cells and displayed low toxicity. With a very low cytotoxic effect against HeLa, compound stands out to be a very good antiparasitic agent and consideration to further evaluate the candidate drug against others cell lines is necessary.