Complexes trans-[RuCl2(nic)(4)] and trans-[RuCl2(i-nic)(4)] as free radical scavengers

This study evaluates the action of the new ruthenium complexes trans-RuCl2( nic)(4)] (I) and trans-[RuCl2(i-nic)(4)] (II) as free radical scavengers. I n our experiments, both compounds acted as scavengers of superoxide anion ( O-2(.-)), hydroxyl radicals (HO.) and nitrogen monoxide (formally known as 'nitric oxide'; NO.). In addition, complexes I and II potentiated the relea se of NO. from S-nitroso-N-acetyl-DL-penicilamine (SNAP), a NO. donor. Comp lex E, but not I, also decreased the nitrite levels in culture media of act ivated macrophages. A hypsochromic shift of lambda (max) and a significant change in half-wave potential (E-1/2) was observed when NO. was added to th e Complex II. Thiobarbituric reactive substance (TBARS) levels were signifi cantly reduced in rats treated for 1 week with Complex H plus tert-butylhyd roperoxide, when compared to rats treated only with tert-butylhydroperoxide . None of the complexes showed cytotoxicity. These findings support the sug gestion that the new ruthenium complexes, especially trans-[RuCl2(i-nic)(4) ] or its derivatives, might provide potential therapeutic benefits in disor ders where reactive nitrogen (RNS) or oxygen (ROS) species are involved. (C ) 2001 Elsevier Science B.V. All rights reserved.