L-CARNOSINE (BETA-ALANYL-L-HISTIDINE) AND CARCININE (BETA-ALANYLHISTAMINE) ACT AS NATURAL ANTIOXIDANTS WITH HYDROXYL-RADICAL-SCAVENGING ANDLIPID-PEROXIDASE ACTIVITIES

Carnosine (beta-alanyl-L-histidine) and carcinine (beta-alanylhistamin e) are natural imidazole-containing compounds found in the non-protein fraction of mammalian tissues. Carcinine was synthesized by an origin al procedure and characterized. Both carnosine and carcinine (10-25 mM ) are capable of inhibiting the catalysis of linoleic acid and phospha tidylcholine liposomal peroxidation (LPO) by the O-2(-->)-dependent ir on-ascorbate and lipid-peroxyl-radica,-generating linoleic acid 13-mon ohydroperoxide (LOOH)-activated haemoglobin systems, as measured by th iobarbituric-acid-reactive substance. Carcinine and carnosine are good scavengers of OH. radicals, as detected by iron-dependent radical dam age to the sugar deoxyribose. This suggests that carnosine and carcini ne are able to scavenge free radicals or donate hydrogen ions. The iod ometric, conjugated diene and t.l.c. assessments of lipid hydroperoxid es (13-monohydroperoxide linoleic acid and phosphatidylcholine hydrope roxide) showed their efficient reduction and deactivation by carnosine and carcinine (10-25 mM) in the liberated and bound-to-artificial-bil ayer states. This suggests that the peroxidase activity exceeded that susceptible ro direct reduction with glutathione peroxidase. Imidazole , solutions of beta-alanine, or their mixtures with peptide moieties d id not show antioxidant potential. Free L-histidine and especially his tamine stimulated iron (II) salt-dependent LPO. Due to the combination of weak metal chelating (abolished by EDTA), OH. and lipid peroxyl ra dicals scavenging, reducing activities to liberated fatty acid and pho spholipid hydroperoxides, carnosine and carcinine appear to be physiol ogical antioxidants able to efficiently protect the lipid phase of bio logical membranes and aqueous environments.