Substituent, structural and positional isomerisation alter anti-oxidant activity of organochalcogen compounds in rats’ brain preparations

The objective of the present study was to elucidate the biochemical potencies of eighteen structurally related organoselenium and organosulfur compounds against Fe(II) induced thiobarbituric acid reactive species (TBARS) formation in rat’s brain homogenate. The efficacies of these compounds (only organosulfur) were further confirmed by radical scavenging and thiol peroxidase-like (TPx) activities. Our data revealed that electron-donating groups significantly improve, while an electron-withdrawing group decreases antioxidant activities. The effect of structural isomerisation proved that electron-donating groups attached to the benzyl moiety at ortho-, meta- or para-positions decreased antioxidant potential. The compound benzyl-p-tolyl selenide (C-6) showed the highest in vitro activity and was selected for the in vivo experiments. Treatment with C-6 at 0, 10, 25 or 50 mg/kg was not associated with mortality, body weight loss or oxidative stress as measured by TBARS production. Similarly it did not inhibit delta-aminolevulinate dehydratase (α-ALA-D) enzyme, in fact treatment with C-6 increased the non-protein thiol content. Exposure to the same compound did not affect plasma transaminase activities or levels of urea and creatinine, indicating negligible toxicity to hepatic and renal tissues. The present study gives useful information for the synthesis of organochalcogens with desired biological and pharmacological potential.