European Journal of Pharmaceutical Sciences 23 (2004) 207–211 Tertiary selenoamide compounds are useful superoxide radical scavengers in vitro Hitoe Takahashi a,∗ , Atsuyoshi Nishina a , Hirokazu Kimura b , Kenji Motoki a , Mamoru Koketsu c , Hideharu Ishihara d a Gunma Industrial Technology Center, 884-1 Kamesato, Maebashi, Gunma 379-2147, Japan b Gunma Prefectural Institute of Public Health and Environmental Sciences, 3-21-378 Kamioki, Maebashi, Gunma 371-0052, Japan c Division of Instrumental Analysis, Life Science Research Center, Gifu University, Gifu 501-1193, Japan d Department of Chemistry, Faculty of Engineering, Gifu University, Gifu 501-1193, Japan Received 3 December 2003; received in revised form 6 April 2004; accepted 21 April 2004 Abstract We investigated the scavenging effects of tertiary selenoamide compounds for super oxide radicals using a highly sensitive and quantitative chemiluminescence method. At 333 nM, tertiary selenoamide compounds scavenged 25.8–81.6% of O 2 - . N-(Phenylselenocarbonyl) piperidine was the most effective scavenger of superoxide radicals. While N,N-diethyl-2-selenonaphthylamide and N,N-diethyl-4-chloroselenobenzamide was a moderately effective scavenger of superoxide radicals. The IC 50 of N-(phenylselenocarbonyl) piperidine and N,N-diethyl-2-selenonaph- thylamide were determined to be 110 and 182 nM, respectively. The results suggest that tertiary selenoamide compounds are useful scavengers of superoxide radicals. © 2004 Elsevier B.V. All rights reserved. Keywords: Tertiary selenoamide; Superoxide radicals; Scavenging effect; Superoxide anion-scavenging activity (SOSA) 1. Introduction Cells in an organism generate a large amount of reactive oxygen species (ROS) as oxygen metabolites. As a result, exposure to ROS is inevitable. ROS, such as superoxide radi- cals (O 2 - ) and hydrogen peroxide (H 2 O 2 ) and hydroxyl rad- icals (OH), cause degeneration of biomacromolecules (i.e., DNA) and induce oxidative stress (Ramirez et al., 2003; Long et al., 1997). It has been suggested that O 2 - is primar- ily generated by mitochondria in various cells and phago- cytes, including granulocytes and monocytes/macrophages in vivo (Fridovich, 1995; Ricci et al., 2003). O 2 - is con- verted to H 2 O 2 in hydrophilic solvents such as water by disproportional reaction (Ueda et al., 1994). In addition O 2 - can react with nitric oxide (NO) and generate highly toxic ROS including ONOO - and nitrogen oxides (NO x )(Hu et al., 2002). Thus, it is important to eliminate O 2 - in vivo. Various antioxidant enzymes including the superoxide dismutases (SODs), catalase, and glutathione peroxidase, ∗ Corresponding author. and antioxidant vitamins (Vitamin C and E) directly scav- enge and eliminate ROS. An important antioxidant enzyme, glutathione peroxidase, contains a selenium molecule in ac- tive domain and effectively scavenges and eliminates H 2 O 2 in vitro and in vivo. In addition, previously studies have demonstrated that selenium compounds such as selenopro- tein protect cells against oxidative stress (Jeong et al., 2002; Taino et al., 2000). It is possible that selenium compounds can effectively scavenge and eliminate ROS. Therefore, this study was performed to determine effectively how tertiary selenoamide (TS) compounds scavenge O 2 - in vitro. 2. Materials and methods 2.1. Materials A chemiluminescent probe for superoxide radicals, which is a Cypridina luciferin analog (2-methyl-6-(p- methoxyphenyl)-3,7-dihydroimidazo-[1,2-a] pyrazin-3-one, or MCLA) was obtained from Tokyo Kasei (Tokyo, Japan), 0928-0987/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ejps.2004.04.011