Synthesis of new 3-(4-methyl-2-arylthiazol-5-yl)-5-aryl-1,2,4-oxadiazole derivatives as potential cytotoxic and antimicrobial agents

Globally cancer is the second leading cause of death; a drug that can cure cancer with the utmost negligible side effects is still a distant goal. Due to increasing antibiotic resistance, microbial infection remains a grave global health security threat. The ongoing coronavirus pandemic increased the risk of microbial and fungal infection. A new series of 3-(4-methyl-2-arylthiazol-5-yl)-5-aryl-1,2,4-oxadiazole (7a-t) have been synthesized. The structure of synthesized compounds was confirmed by the spectrometric analysis. The newly synthesized compounds were screened for cytotoxic activity against breast cell lines MCF-7 and MDA-MB-231. Against the MCF-7 cell line compounds 7f, 7 g and 7n showed excellent activity with GI50 0.6 mu M to <100 nM concentration. Compound 7b showed good activity against MDA-MB-231 cell line with GI50 47 mu M. The active derivatives 7b, 7e, 7f, 7 g and 7n were further evaluated for cytotoxicity against the epithelial cell line derived from the human embryonic kidney (HEK 293) and were found nontoxic. The thiazolyl-1,2,4-oxadiazole derivatives were also screened to evaluate theirs in vitro antimicrobial potential against Escherichia coli (NCIM 2574), Proteus mirabilis (NCIM 2388), Bacillus subtilis (NCIM 2063), Staphylococcus albus (NCIM 2178), Candida albicans (NCIM 3100) and Aspergillus niger (ATCC 504). Amongst the 7a-t derivatives, six compounds 7a, 7d, 7f, 7n, 7o, 7r showed good antifungal activity against C. albicans and eight compounds 7c, 7d, 7 g, 7h, 7i, 7k, 7l and 7o showed good activity against A. niger. The potential cytotoxic and antifungal activity suggested that the thiazolyl-1,2,4-oxadiazole derivatives could assist in the development of lead compounds for the treatment of cancer and microbial infections.