Three Schiff bases were synthesized by reaction of different benzaldehydes with amino acids. The characterization of these compounds was performed using IR spectroscopy, molecular calculations, thin-layer chromatography, determining the melting point and other physical characteristics. IR spectra for imino groups (C=N), which are characteristic of Schiff bases, show stretching frequency from 1629 to 1654 cm-1. The obtained spectral results were confirmed by molecular calculations using the density functional theory (DFT) and were performed before experimental work. The DFT global chemical reactivity descriptors were calculated and used to predict their relative stability and reactivity of synthesized compounds. The antimicrobial assay of all compounds were screened for Grampositive bacteria species: Staphylococcus aureus ATCC 25923; Methicillin-resistant Staphylococcus aureus: MRSA ATCC 33591; Bacillus subtilis ATCC 6633; and Enterococcus faecalis ATCC 29212, Gram-negative: Salmonella enterica ATCC 31194; Pseudomonas aeruginosa ATCC 9027; Escherichia coli ATCC 25922; Extended Spectrum Beta-Lactamase producing E. coli: ESBL E. coli ATCC 35218, and one yeast Candida albicans ATCC 1023.The highest values of inhibition zones were recorded for compound1, followed by the compound 3, while compound 2 performed inhibitory effect just in case of MRSA. DFT calculations show that antimicrobial activity has a good correlation with chemical reactivity descriptors obtained Schiff bases.

A new low potential electrochemical sensor for determination of L-cysteine based on carbon electrodes modified with Ru(III) Schiff base complex, multi-walled carbon nanotubes and Nafion is presented. Cyclic voltammetry, differential pulse voltammetry and flow injection analysis were employed. Measurements were carried out using Britton-Robinson buffer (pH 5.50). The results showed that addition of multi-walled carbon nanotubes to Ru(III) complex modified glassy carbon and screen printed carbon electrodes gives increased current signals at the potential where oxidation of L-cysteine occurs. Flow injection amperometric measurements were performed at the operating potential +0.15 V vs. Ag/AgCl (3 M KCl) electrode and showed fast electric current response for L-cysteine oxidation, demonstrating good reproducibility and stability. The sensor has a detection limit of 0.11 mg L -1 and a dynamic range of 50-500 mg L -1 . The repeatability was calculated as 2.8 %. New sensor was used for the determination of L-cysteine in pharmaceutical products.