Synthesis, structure–activity relationships, and in vitro antibacterial and antifungal activity evaluations of novel pyrazole carboxylic and dicarboxylic acid derivatives

•Novel pyrazole-3-carboxylic and 3,4-dicarboxylic acid derivatives were synthesized.•The antibacterial and antifungal activities of the compounds were screened.•Tested compounds depicted stronger inhibition effect on Candida albicans.•SAR of the compounds on C. albicans investigated by electron-conformational method.

A series of pyrazole-3-carboxylic acid and pyrazole-3,4-dicarboxylic acid derivatives were synthesized, the structures were confirmed by their NMR (1H and 13C) and FT-IR spectra, and elemental analyses. The antibacterial and antifungal activities of the compounds against five bacterial and five fungal pathogens were screened using modified agar well diffusion assay. Most of the molecules have inhibitory effects on both standard and clinical Candida albicans strains. However, only the molecules 8, 10, 21, and 22 demonstrate some inhibitory effects on Candida parapsilosis, Candida tropicalis, and Candida glabrata strains. The structure–antifungal activity relationships of the compounds on the C. albicans strains were investigated by electron-conformational method. The pharmacophores and antipharmacophores responsible for the inhibition and non-inhibition of the C. albicans strains were obtained by electronic and geometrical characteristics of the reactive fragments of the molecules. These fragments along with the associated parameters can be used in designing the future more potent antifungal agents. It has been shown that both the positions of electronegative atoms like F and O in the pyrazole substituents and the amount of the associated charges on such atoms are crucial in regulating the strength of antifungal activity for the C. albicans strain.

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