Bisbenzoxazole Derivatives: Design, Synthesis, in Vitro Antimicrobial, Antiproliferative Activity, and Molecular Docking Studies

Four series of bisbenzoxazole derivatives were designed, synthesized, and screened for antiproliferative and antimicrobial activities. Generally, all synthesized bisbenzoxazoles (9-24) displayed significant antiproliferative activity; these effects were shown to be related to oxazole rings and substituents in bisbenzoxazole compounds. Especially, the series bearing chloro-substituent (9-12) exhibited better antiproliferative activity with higher selectivity than the other series (13-24); the IC50 values were observed in the range of 0.045-0.342 mu M. Interestingly, only the compound with a nitro substituent (22) showed maximum potency with an IC50 value of 0.011 mu M, which is two-fold more active than the standard drug methotrexate, with moderate selectivity. The compounds bearing fluoro-substituent (14-16) were found to exhibit potent antibacterial activity against the Gram-positive Enterococcus faecalis, with a MIC value of 62.5 mu g/mL, and moderate activity against Gram-negative bacteria and fungi. Only the compound 23 showed potent activity against Escherichia coli, with a MIC value of 62.5 mu g/mL. In order to better evaluate the activity results, crystal structures of five different proteins Human Anaplastic Lymphoma Kinase (PDB ID: 2XP2), CYP2C8dH complexed (PDB ID: 2NNI), factor-human kinase-beta enzyme IKK-beta enzyme (PDB ID: 4KIK), a tubulin heterodimer complex containing alpha and beta sub-units (PDB ID: 1Z2B) and penicillin-binding protein 4 (PBP4) from Enterococcus faecalis (PDB ID: 6MKI) were used in the docking study to examine antiproliferative and antimicrobial activity. Finally, an ADMET screening test was applied to determine the drug-like, toxicological, and optimum physicochemical properties for all of the synthesized compounds. The strategy applied in this research may act as a perspective for the rational design of potential anticancer drugs.