1,1,2-Tris-organoselenide alkene derivatives, but not 1,2-bis-organoselenide alkene derivatives, inhibited δ-aminolevulinate dehydratase activity from human erythrocytic cells in vitro

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Organochalcogens are important intermediates and useful reagents in organic synthesis. Recent data from our laboratory demonstrated that bis and tris-selenide alkene derivatives are attractive synthetic targets because of their chemio-, regio- and stereo-selective reactions. Since the erythrocytic δ-aminolevulinate dehydratase (δ-ALA-D) activity could be an important indicator of toxicity, this report investigated bis and tris-selenide alkene derivatives effects on blood δ-ALA-D in vitro. To investigate the mechanisms by which these compounds inhibit human blood δ-ALA-D activity, a thiol reducing agent or zinc chloride were used. 1,2-Bis-selenide alkene derivatives 1a (R = 4-MeOC 6H 4), 1b (R = 4-ClC 6H 4) and 1c (R = 2,4,6-Me 3C 6H 2) did not inhibit human blood δ-ALA-D activity. 1,1,2-Tris-selenide alkene derivative 2a (R = C 6H 5) was the most potent δ-ALA-D inhibitor. Compounds 2b (R = 4-MeOC 6H 4) and 2c (R = 4-ClC 6H 4) displayed similar inhibitory potency towards δ-ALA-D activity. Dithiothreitol, a hydrophobic SH-reducing agent, was able to restore and to protect δ-ALA-D activity inhibited by tris-selenide alkene derivatives. Conversely, ZnCl 2 did not alter the enzyme inhibition induced by tris-selenide alkene derivatives. From these findings we suggest that 1,1,2-tris-selenide alkene derivatives inhibited δ-ALA-D activity by an interaction with essential sulfhydryl groups for the enzyme activity.