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An influence of meso-tetraphenylporphyrin (TPPH 2 ) and its derivatives, i.e. meso-tetrakis(3,5-di-tert-butyl-4hydroxyphenyl)porphyrin (R 4 PH 2 ), meso-tetra(4-sulfonatophenyl)porphine ((HO 3 S) 4 TPPН 2 ), in the presence of mercury and tin compounds on the rate of hydrogen peroxide decomposition by hemolysate of laundered human blood erythrocytes was studied. The decrease of the decomposition rate of hydrogen peroxide by erythrocytes in the presence of TPPH 2 and mercury (HgCl 2 , CH 3 HgI, Hg(NO 3 ) 2 ·H 2 O) or tin ((CH 3 ) 2 SnCl 2 , (n-C 4 H 9 ) 3 SnCl, (n-C 4 H 9 ) 2 SnCl 2 , (C 6 H 5 ) 3 SnCl, (C 6 H 5 ) 2 SnCl 2 )) compounds was ascertained. (n-C 4 H 9 ) 3 SnCl, which is used as biocidal additive in paints, is the most toxic in this row; the addition of this compound decreases the rate of H 2 O 2 decomposition by 70%. The influence of organotin compounds on the reaction rate depends on the nature of organic group and, in the case of butyl and methyl derivatives, on the quantity of these groups. The influence of addition of the extremely toxic methylmercury salts on the decomposition rate of hydrogen peroxide does not differ from the influence of inorganic mercury salts. The decrease of the H 2 O 2 decomposition rate in the presence of tin and mercury compounds may be connected with inhibition of catalase enzyme. At these conditions, an excess of hydrogen peroxide is formed, what brings to the change of permeability of biomembranes and oxidative stress. When (HO 3 S) 4 TPPН 2 is added in erythrocytes hemolysate the rate of enzymatic reaction is similar to control one. So an inclusion of sulfo group on the periphery of porphyrin molecule TPPH 2 eliminates the decrease of H 2 O 2 decomposition rate. The UV-vis spectrum of (HO 3 S) 4 TPPН 2 indicates the broadening and a small hypsochromic shift of the Soret band (5 nm) if compared with that of TPPH 2 . Absorption intensity at the Q-band region (500-600 nm) is also decreased. An addition of R 4 PH 2 to erythrocytes hemolysate, containing tin compounds, causes an increase of catalase activity, thus the decrease of H 2 O 2 decomposition rate by toxicants is eliminated. Maximum efficiency of R 4 PH 2 additives was established in the presence of (n-C 4 H 9 ) 2 SnCl 2 . An addition of TPPH 2 leads to the further reduce of the rate of H 2 O 2 decomposition by erythrocytes hemolysate in the presence of (CH 3 ) 3 SnCl and (n-C 4 H 9 ) 3 SnCl. The additives of sulfoporphyrin in hemolysate, containing CH 3 HgI, (CH 3 ) 3 SnCl, Hg(NO 3 ) 2 , HgCl 2 , results in increasing of H 2 O 2 decomposition rate. Water-soluble (HO 3 S) 4 TPPН 2 decreases the negative impact of tin and mercury compounds to the rate of enzymatic reactions. An increase of the rate of hydrogen peroxide decomposition by hemolysate of the laundered human blood erythrocytes, caused by R 4 PH 2 in the presence of organotin derivatives, contributes to the antioxidant status of blood erythrocytes in the conditions of the toxicants action.

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Protecting Effect of the Free Base Porphyrins on the Rate of Hydrogen Peroxide Decomposition by Hemolysate of Human Blood Erythrocytes in the Presence of Mercury and Tin Compounds