Synthesis, Antimicrobial, and Antioxidant Activities of Chalcogen-Containing Nitrone Derivatives from (R)-citronellal.

The main constituents of (L) Rendle and C. (DC) Stapfessential oils are ()-citronellal and citral, respectively. Organochalcogen compounds can boost the biological activities of natural products. Several chalcogen-containing nitrones derived from ()-citronellal and citral were prepared and evaluated for their antimicrobial and antioxidant activities. The antimicrobial activity was evaluated by the disc diffusion test and the antioxidant properties were evaluated in vitro by DPPH (1,1-diphenyl-2-picryl-hydrazyl), ABTS (2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid), and FRAP (ferric ion reducing antioxidant power) assays. In the antimicrobial assay, ()-,3,7-trimethyl-3-(phenylthio)oct-6-en-1-imine oxide exhibited halos between 21.5 mm ( O157:H7) and 26.0 mm (), while ()-,3,7-trimethyloct-6-en-1-imine oxide presented halos between 22.5 mm ( O157:H7) and 31.0 mm (). ()-,3,7-Trimethyl-2-(phenylthio)oct-6-en-1-imine oxide showed the lowest minimal inhibitory concentration (MIC) value against (0.48 mM), and was the most potent bactericide, with a minimal bactericidal concentration (MBC) of 0.52 mM for O157:H7. In the antioxidant assays, , , and (()-3,7-dimethyl-2-(phenylselanyl)oct-6-enal oxime) were the most actives in the DPPH, ABTS, and FRAP assays, respectively. The presence of a phenylthio group in the nitrone increases its antimicrobial activity against Gram-positive and Gram-negative foodborne pathogens in the disk diffusion test and the antioxidant activity in vitro.