Induction of the Antioxidant Activity by Selenium Compounds in the <i>Aspergillus niger</i> Mycelium

Abstract

Investigation of the antioxidant activity (AOA) induction by selenium compounds (Na2SeO3, diacetophenonyl selenide (DAPS-25), L-selenocystine) in various organisms is interesting as a protection from stress induced cell membranes damages. A comparative analysis of the antioxidant activity of 23 amino acids was performed by coulometric titration with electrogenerated bromine and iodine. The activity decreases in the order: cystine tryptophan selenocystine tyrosine 3,3'-dimethyl-L-selenocystine methionine. Only amino acids with sulfhydryl and selenol groups as more active reductants can interact with the electrogenerated iodine: cysteine selenocysteine threo-3-methyl-L-selenocysteine. Probably the correction of the antioxidant status at the amino acids level is based on the sulfhydryl and selenol groups in radicals. In case they are not enough, cystine, selenocystin, tryptophan, tyrosine, and methionine will act as scavenger-reductants. It was found that selenium compounds dose-dependently induce the total antioxidant activity of the A. niger mycelium and affect indicators of the antioxidant status (amino acid composition and catalase activity), which in turn stimulates the biomass accumulation. DAPS-25 and sodium selenite treatment at the high doses (0.025 mg Se/L) caused the greatest effect on the total AOA induction (3.4–5.5 times). Lower concentrations (0.0025–0.00025 mg Se/L) had a lesser effect (25.8–41.7%). Activity in samples with L-selenocystin increased by 1.6–43.3%. It is noted that the iodine antioxidant activity in the mycelium was generally lower than the bromine one.