Oxidative biochemistry centered about 35 years ago on the one-electron reduction of H₂O₂ by Fe²⁺, the Fenton reaction, to yield HO^· and a Fe(III)-complex. The discovery that NO^· is formed in vivo and that it reacts with O₂^·− at a diffusion-controlled rate led to ONOO⁻ as an additional oxidant. The rate constant of the Fenton reaction is 53 M⁻¹s⁻¹ up to about pH 4, but above it the rate constant increases linearly with pH.  This acceleration of the Fenton reaction led to the hypothesis that above pH 5 formation of FeO²⁺ predominates.  Thermodynamically, this species is comparable to HO^· as an oxidant.  HCO₃⁻ accelerates the reaction even more, and convincing evidence has been presented that the complex of Fe²⁺ with CO₃²⁻ reacts with H₂O₂ to form CO₃^·− and a Fe(III)-complex, conceivably via FeO²⁺ as an intermediate. The rapid reaction of ONOO⁻ with CO₂ (k > 10⁷ M⁻¹s⁻¹) leads to ONOOCO₂⁻ that, depending on the CO₂ concentration, yields varying amounts of NO₂^· and CO₃^·−.  These two oxidizing radicals together nitrate aromatic residues. Compared to 35 years ago, oxidative biochemistry is no longer concerned with the indiscriminate oxidations and additions of HO^·, but with the more selective reactions of CO₃^·− and NO₂^·.

The global pandemic crisis affected almost every society and economy, challenged almost every health system worldwide. Above all, governments and non-governmental organizations had to fight the misinformation and conspiracy theories placed by the social and mass media. All of this had a profound impact on the public in terms of vaccine safety and the advantages of vitamin use in fighting the virus. This fear has opened doors to alternative medicines such as supplements (vitamins, minerals, herbal products, oils) that may have profound effects on the immune system. To determine the pattern of use of supplements during the pandemic in healthy individuals who tested negative for SARS-CoV-2. The 33 healthy individuals tested negative for SARS-CoV-2 in the pandemic period were included (Group 1). Total antioxidant power, iron-reducing (PAT), and plasma peroxides (d-ROMs) were measured using FRAS5 analytical photometric system and are reported in equivalents of ascorbic acid and H2O2, respectively. The oxidative stress index (OSI) was automatically calculated by the software. The obtained values were compared with 30 healthy individuals analyzed prior to the pandemic (Group 2). The mean values for oxidative stress parameters in Group 1 vs Group 2 were: d-ROMs 418 vs 266 U. Carr, PAT 3862 vs 2554 U. Carr, and OSI 111 vs 36. In all comparisons, a statistically significant difference was obtained (p<0.05, t-test). Individuals belonging to Group 1 had reported that they have consumed daily doses of Zinc (30 mg), Vitamin C (at least 1000 mg) and Vitamin D (at least 2000 IU) in a period of >1 month. Several of them have also used Isoprinosine, magnesium, and selenium. Uncontrolled intake of supplements can have a profound effect on the pro- and antioxidant balance resulting in interruption of the phycological balance and leading to increased oxidative stress index in otherwise healthy individuals. 

A 60-day experiment was conducted to investigate the impact of dietary sulfur amino acids (AA) on altered haemato-biochemical and redox parameters of Inshas cockerel chicks raised under restricted feeding. Male Inshas strain chickens were divided into five groups, each with five replicates of eight birds. The control group received the full National Research Council (NRC) requirements (100%). The other groups received diets meeting 90% of NRC requirements: 90% NRC; 90% NRC+Methionine; 90% NRC+Cysteine; and 90% NRC+both Methionine and Cysteine (AA-mix). AA supplementation improved growth performance compared to the control group. The birds that were given a combination of AA supplementation exhibited the highest body weight and carcass weight compared to other groups. AA supplementation improves blood physiological characteristics by reducing damage caused by feed restriction conditions. Serum parameters, including aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, alkaline phosphatase, gamma-glutamyl transpeptidase, and total protein concentration, showed decreased levels. Treatment with mixed AA maintained urea and uric acid concentrations at a level similar to the control group. Remarkably, a combination of AA treatments reduced the negative effects of feed restriction on young male chickens by enhancing the overall antioxidant capacity and activity of antioxidant enzymes in liver tissue (glutathione S-transferase, total superoxide dismutase, glutathione peroxidase, and amount of total glutathione), and decreased the malondialdehyde concentration. Feed restriction impacted liver histological structure, where hepatocytes were susceptible to feed restriction and included numerous cytoplasmic vacuoles, congested blood vesicles, lymphocytic infiltration, and pyknotic nuclei in treated cockerels. AA therapy restored most hepatic histological abnormalities. The findings suggest that AA supplementation significantly mitigated the adverse effects of feed restriction by improving haemato-biochemical parameters and hepatic redox status.

Acknowledgement: The authors extend their appreciation to the Department of Animal and Poultry Production, Faculty of Agriculture, Minia University, Egypt.