SYNTHESIS AND ANTIOXIDANT ACTIVITY OF THIADIAZINE DERIVATIVES WITH PHENOLIC FRAGMENTS

Abstract

A series of thiocarbohydrazones based on 3,5-di-tert-butyl-4-hydroxybenzaldehyde, salicylaldehyde, vanillin and 4,6-di-tert-butyl-2,3-dihydroxybenzaldehyde were synthesized. The reaction between thiocarbohydrazones and bromoacetylcoumarin was used to obtain and characterize a number of thiadiazine derivatives containing a phenolic fragment. The yields were 56–90%. The structural properties of the synthesized substances were studied by IR-Fourier, 1H, 13C NMR spectroscopy. In the IR spectra of thiadiazines there are characteristic bands of the stretching vibrations of the OH group (3622 cm-1), N-H bond (3450 cm-1), double bonds C=C and C=N 1608 and 1541 cm-1, respectively. In contrast to the spectrum of the starting compounds, there is a peak corresponding to vibrations of the C=O bond (1722 cm-1), which appeared due to the coumarin fragment. The 1Н NMR spectra of the obtained compounds contain peaks at 3.9 ppm, corresponding to the protons of the thiadiazine fragment. There are no signals at 6.8 ppm, related to the CH proton of the thiazole ring, and there is also a set of peaks in the region of 7.5-8.4 ppm., characteristic of the coumarin ring. Antioxidant activity of all products was determined in vitro: radical cation inhibition activity was determined using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) and electron donating activity was determined by ferric reduction ability using the ferricyanide/Prussian blue method. In both cases, agidol was used as a standard. All tested substances showed higher activity in both tests compared to the standard. The best antioxidant properties in both methods were shown by the derivative of 4,6-di-tert-butyl-2,3-dihydroxybenzaldehyde, thiadiazine based on salicylaldehyde also showed high antiradical activity, and thiadiazine with a fragment of 2-methoxyphenol showed good ferric-reducing properties.