SYNTHESIS AND STUDY OF ANTIOXIDANT ACTIVITY OF N-HETERYLTHIO- AND N-ETHYLXANTHOGENATO-1,4-BENZOQUINONEIMINES

Abstract

N-substituted 1,4-quinoneimines have a wide spectrum of biological activity. The stabilizing property of N-substituted p-quinonemono- and diimines is known, which is related to their antioxidant activity. Derivatives of N-substituted 1,4-benzoquinoneimines are used as antioxidants and stabilizers. For example, stabilization of fats, oils, unsaturated compounds with N-phenyl-1,4-benzoquinonimine was proposed. The aim of this work was the synthesis and study of the antioxidant activity of N-heterylthio- and N-ethylxanthogenato-1,4-benzoquinoneimines. N-Heterylthio-1,4-benzoquinonimines were synthesized by the reaction of N-chloro-1,4-benzoquino-4-nimines with the corresponding heterocyclic mercaptans in acetone. The reaction of quinonimines with mercaptobenzoxazole was difficult, so it was carried out with the sodium salt of mercaptobenzoxazole in ethyl alcohol. The reaction products were bright orange crystals. The composition and structure of the synthesized compounds was established based on the results of elemental analysis and the study of PMR spectra. An in vitro method based on the reaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) dissolved in ethanol was used to assess antioxidant activity (AOA). As a result of the reduction of DPPH with an antioxidant, a gradual discoloration of the DPPH solution in ethanol was observed, which was determined by the change in optical density at 517 nm on a spectrophotometer. The radical-absorbing activity (RAP) of the compound was defined as the ratio of the difference in the value of the optical densities of the DPPH solution and the solution containing the test substance and DPPH to the optical density of the DPPH solution. High levels of antioxidant activity were found for 4-(benzo[d]thiazol-2-ylthioimino)-2,5-dimethylcyclohexa-2,5-dienone, 4-(1H-benzo[d]imidazol-2-ylthioimino)-2, 6-dimethylcyclohexa-2,5-dienone, and 2,6-dimethyl-4-[(4H-1,2,4-triazol-5-ylsulfanyl)imino]cyclohexa-2,5-dienone. It was established that 2,6-dimethyl-4-{[(ethoxymethanethioyl)sulfanyl]imino}cyclohexa-2,5-dienone neutralizes free radical by 91% after 20 minutes of interaction with the stable free radical DPPH.