Facile Synthesis of Benzimidazoles via Oxidative Cyclization of Acyclic Monoterpene Aldehyde with Diamines: Studies on Antimicrobial and in Vivo Evaluation of Zebrafish.

Citral (1a), a bioactive component of Cymbopogon citratus (lemongrass) could be isolated and semi-synthetic analogs synthesized with improved therapeutic properties. Herein we first report describes citral (1a) as a primary material for the synthesis of benzimidazole derivatives between various o-phenylenediamines (2a-l) in the presence of Diisopropylethylamine (DIPEA) as a commercially available environmentally benign base, ethanol as a green solvent and the yield of all benzimidazole derivatives (3a-l) was between 68-76 %; The semi-synthetically prepared benzimidazole derivatives (3a-l) were assessed for their anti-bacterial and anti-fungal properties. The benzimidazole compounds (3a-b, and 3g-j) exhibit good anti-microbial activity. In addition, in silico study was carried out to determine the specific binding affinity of the diamine halogen substituted benzimidazole derivatives to the specific target proteins. In silico analysis revealed a high correlation between docking results and experimental results. Finally, benzimidazole demonstrated significant antibacterial and antifungal activity. Zebrafish embryos were subjected to In vivo toxicological test found that all of the benzimidazole compounds (3a-l) were non-toxic and had low embryotoxicity after 96 h, with an LC50 of 36.425 μg, which could facilitate the design of novel antimicrobial agents using a cost-effective method.