Журнал "Макрогетероциклы"

Margarita N. Kolyada,^а Victoriya P. Osipova,^a@ Nadezhda T. Berberova,^b Yuri T. Pimenov,^b and Elena R. Milaeva^c

^aSouthern Scientific Center of RAS, 344006 Rostov-on-Don, Russia

^bAstrakhan State Technical University, 414025 Astrakhan, Russia

^cLomonosov Moscow State University, Department of Chemistry, 119991 Moscow, Russia

^@Corresponding author E-mail: vposipova@rambler.ru

DOI: 10.6060/mhc160542o

Macroheterocycles 2017 10(1) 57-61

Lipid peroxidation (LP) is one of the major factors of pathologies of various genesis including the toxic impact of heavy metals. The promising polyfunctional hybrid antioxidants are the compounds containing both porphyrin and sterically hindered phenol moieties that act by different mechanisms of lipid peroxidation inhibition. The influence of synthetic meso-substituted porphyrins – meso-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin (R₄PH₂) and its analogue, free base of meso-tetraphenylporphyrin (TPPH₂) which does not bear 2,6-di-tert-butylphenol antioxidant fragment on the lipid peroxidation of fish fodder in the presence of ((С₄Н₉)₃SnCl, (С₄Н₉)₂SnCl₂, (С₆Н₅)₃SnCl and (С₆Н₅)₂SnCl₂)in comparison with widely used antioxidants (α-tocopherol, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol (BHT, ionol)) has been studied. Tributyl- and triphenyltin chlorides are known prooxidants, and despite the fact that their application as biocides is strongly restricted, nevertheless, they accumulate in bed silt, in aquatic media, hydrobionts and therefore are detected in various fish products including fish fodder.

In this study, we measured the level of primary LP products – hydroperoxides (LOOH) in the lipids extract of fish fodder ОТ-6A. The experiment has been performed at 25±1 ^○C once in a week in the period of 12 weeks. The concentration of porphyrins and antioxidants was 150 mg per 1 kg of fish fodder (0.015 %) that is the normal content of antioxidants in the fodder ≤ 0.02 % (200 mg/kg). The concentration of organotins was 15 µmol/g. It has been shown that tin compounds as additives to the fish fodder lipids increase the level of LOOH that does not depend on the organic group nature,  however, is influenced by their number. Disubstituted organotin compounds (С₄Н₉)₂SnCl₂, and (C₆H₅)₂SnCl₂ demonstrate the highest activity – the level of LP products increases 6–7 times when compared to control without any additives. The free base of meso-tetraphenylporphyrin (TPPH₂) which does not bear 2,6-di-tert-butylphenol antioxidant fragment acts as a prooxidant in lipids autooxidation and in the media containing organotins as well. meso-Tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin (R₄PH₂) is an effective inhibitor of LP in fish fodder both in the absence of toxicants and in the presence of organotins as LP promoters. We propose that R₄PH₂ is oxidized to form a relatively stable biradical which is transformed to the porphodimethenediquinomethide and the main product – meso-tetrakis(3,5-di-tert-butyl-4-quinomethide)porphyrinogene. The oxidation steps are reversible that influences the high antioxidant activity of R₄PH₂.Moreover, the concentration of R₄PH₂ was less than the concentration of widely used antioxidants under investigation, however, the activity was higher. Therefore, we can conclude that inhibitory activity of R₄PH₂ studied in model system of LP of fish fodder is higher that the activity of widely used antioxidants (α-tocopherol, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol (ionol)). These results allow one to suggest that meso-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin (R₄PH₂) is a promising antioxidant and detoxification agent which can be applied as stabilizer of fish fodder.

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