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Study of structure-bioactivity relationship of three new pyridine Schiff bases: Synthesis, spectral characterization, DFT calculations and biological assays

Abstract

Abstract Schiff bases exhibit a broad range of applications, including their use as catalysts, stabilizers, dyes, and intermediates in organic synthesis; and biological activities, such as antifungal properties. In this work, we synthesized and characterized three new pyridine Schiff bases L3 ((E)-2-{[(3-aminopyridin-4-yl)imino]-methyl}-4,6-di-chloro-phenol), L4 ((E)-2-{[(3-aminopyridin-4-yl)imino]-methyl}-6-chloro-phenol), and L5 ((E)-2-{[(3-aminopyridin-4-yl)imino]-methyl}-4-methyl-phenol) to explore the structure-bioactivity relationship as antifungal agents. We also synthesized and characterized a diamine-derived Schiff base (L6) that is similar to (E)-2-{[(3-aminopyridin-4-yl)imino]-methyl}-4,6-di-tert-butyl-phenol (L2, which previously demonstrated antifungal activity), but lacks the pyridine ring, to assess the impact of this structural modification into biological properties. All the Schiff bases were characterized by FTIR, 1H and 13CNMR, DEPT, HHCOSY, TOCSY, UV-vis, MS, cyclic voltammetry, DFT calculations, and NBO to assess the stability of the intramolecular hydrogen bond (IHB). In addition, we determined the antimicrobial properties by obtaining the minimal inhibitory concentration (MIC) for Cryptococcus spp. (yeast) and Salmonella enterica (bacteria), and growth inhibition of Botrytis cinerea (mold). We found that the antifungal activity of these Schiff bases relied on the nitrogen atom in the pyridine ring, where antifungal activity can be modulated by different substituents in the phenolic ring. In this work we provide data supporting a correlation between structure and bioactivity in this kind of Schiff bases. The understanding of structural prerequisites for antimicrobial activity could contribute for designing new drugs. Keywords: Schiff base, intramolecular hydrogen bonds, DFT, NBO, antifungal, Cryptococcus, Salmonella, Botrytis cinerea

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Supplementary files

Publication details

The article was received on 22 Jan 2018, accepted on 15 Apr 2018 and first published on 16 Apr 2018


Article type: Paper
DOI: 10.1039/C8NJ00390D
Citation: New J. Chem., 2018, Accepted Manuscript
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    Study of structure-bioactivity relationship of three new pyridine Schiff bases: Synthesis, spectral characterization, DFT calculations and biological assays

    A. Carreño, C. Zuñiga, D. Paez-Hernandez, M. Gacitua, R. Polanco, C. Otero, R. Arratia-Perez and J. Fuentes, New J. Chem., 2018, Accepted Manuscript , DOI: 10.1039/C8NJ00390D

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