Antibacterial activity and structure-activity relationships of Schiff bases on Staphylococcus aureus by microcalorimetry

Abstract

The growth of Staphylococcus aureus under the action of six kinds of Schiff bases (A, B, C, D, E, F) was studied by means of microcalorimetry. Growth constant k and inhibition ratio I were calculated. Also, the antibacterial activity, the action characteristics and the structure-activity relationships of the compounds on S. aureus were analyzed. Results indicate that B, F show good antibacterial activity (IC 50 : 293.6 mg • L −1 and 307.8 mg • L −1 ), D, E show moderate antibacterial activity (IC 50 : 966.3 mg • L −1 and 1 126.7 mg • L −1 ), and A, C just show weak antibacterial activity (IC 50 ∨ 1 200 mg • L −1 ). The I-c curves mainly present a straight line shape for B, D, E and F, but an inverse "S" shape for A and C. Structure-activity relationships analysis suggests that the species and position of the substituents determine the antibacterial activity of these Schiff bases, and the charge density distribution is one of the most important influencing factors.Since it has become a pressing issue of human health that drug-resistant bacterial pathogens appear and spread quickly within the global range [1][2][3][4] , the need for the discovery of novel antibacterial agents is a reality. Having been studied for more than one hundred years, Schiff base compounds are found to have various characteristics, which result in their applications in biology [5] , analysis and material industry [6] , in addition to their important roles in catalysis and organic synthesis [7] . For a long time, pharmacological activity, especially the anti-tumor and antibacterial activity, is one of the major research fields of Schiff base compounds [8,9] . Also, Schiff bases have attracted much more attention recently as the synthetic drugs against bacteria [10] . Although lots of Schiff bases compounds with good antibacterial activity have been discovered [11,12] , few of them are used in clinical applications. It is necessary to do more in-depth studies especially the systematical studies on structure-activity relationships, which are significant in finding novel antibacterial agents for clinical use. However, one of the hindrances is that it is difficult to accurately measure the biological activities of the compounds by common biological methods because of their poor water solubility.As a non-invasive and non-destructive technique, microcalorimetry has long been used in the

Synthesis, Spectroscopic, SQUEEZE method/XRD interactions, linear and Nonlinear Optical properties, and antibacterial effect of the ligand/copper(II) complex tetradentate Schiff base: Experimental and Theoretical Studies

“…In disc diffusion method the diameter of the inhibition zone is related to the sensitivity of the isolate and to the diffusion rate of the drug through the agar medium [64]. Diffusion rate of chemical compounds on agar plates may be affected by other factors as: solubility, dipole moment, molecular mass and hydrophobicity [65]; Additionally, chemicals structure might influence their antibacterial activities [66], generally, the electronic nature (electron withdrawing and electron releasing) and position of substituents of the phenyl ring determines the antimicrobial activities [67], studies of structure activity relationship revealed that the presence of electron-withdrawing group Br on the para position of the phenyl rings has a positive effect on the antibacterial activity [68].…”

Synthesis and Characterization of New Oxazepines Compounds Derived From D- Galactose

“…They also form basic units in certain dyes [1]. Schiff bases are reported to exhibit antibacterial [2][3][4][5], antifungal [6] and antitumor activity [7]. In addition, the compounds and their metal complexes exhibit interesting photophysical properties [8].…”