Owing to the rise in antimicrobial and chemotherapeutic drug resistance, there is a desperate need to formulate newer as well as more effective agents. With this perspective, here we outline the synthesis of two novel gemini surfactants with different substitutions at the nitrogen atom of the benzimidazolium ring. Both the compounds induced significant reductions in Candida growth in various yeast strains. The reduction in Candida growth seemed likely through the reduction in ergosterol biosynthesis: a sterol constituent of yeast cell membranes. Different concentrations of both compounds were used to determine the cellular ergosterol content which indicates an important disordering of the ergosterol biosynthetic pathway. Cytotoxic studies were carried out using HEK 293 (human embryonic-kidney cells) and Galleria mellonella larvae (an in vivo model of antimicrobial studies). Administration of both the compounds to G. mellonella larvae diseased by the yeast Candida albicans resulted in increased survival indicating their in vivo activity.

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2‐Hydroxy‐naphthaldehyde based heterocyclic Schiff base derivatives (1 a‐1 h) were prepared and characterized by multi‐spectroscopic techniques and elemental analysis. Antibacterial activity of all the compounds was tested against Streptococcus pneumoniae, Enterococcus faecalis, Pseudomonas aeruginosa, Salmonella enterica, Klebsiella pneumoniae and Escherichia coli bacterial strains. The antifungal potential of the synthesized compounds was also tested against three Candida strains (Candida albicans, Candida glabrata and Candida tropicalis). In the antibacterial activity, the compounds showed high MIC values and thus found less potent against all the tested bacterial strains. Interestingly, compounds 1 b and 1 c exhibited significant activity with MIC 125 μg/ml against all the tested fungal strains. Hemolytic assay against human RBCs revealed that compounds 1 b and 1 c showed less toxicity than the standard drug fluconazole at each tested concentration (25‐1000 μg/ml). In growth kinetics studies, compounds 1 b and 1 c significantly inhibited the growth of Candida cells at 2MIC and MIC concentrations. The interaction ability of lead compounds (1 b and 1 c) with Ct–DNA was carried out by absorption, fluorescence, hydrodynamic, cyclic voltammetery measurements and circular dichroism. Results suggested that compound 1 b and 1 c bind to Ct–DNA via an intercalative mode supported by molecular docking studies. The antioxidant potential of heterocyclic derivatives 1 b and 1 c was estimated by DPPH free radical and hydrogen peroxide assay which confirm that compounds exhibited significant antioxidant activity.

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