Effects of virgin olive oil phenolics on scavenging of reactive nitrogen species and upon nitrergic neurotransmission

The major phenolics from the polar fraction of virgin olive oil (caffeic ac id, oleuropein, tyrosol and hydroxytyrosol) have well-established antioxida nt activities but their effects on reactive nitrogen species and nitrergic neurotransmission have not been fully investigated. The three catechol comp ounds were active as scavengers of nitric oxide generated spontaneously fro m the decomposition of sodium nitroprusside (approximate to 50% inhibition achieved at 75 muM), and had similar ability to scavenge chemically generat ed peroxynitrite, as determined by an alpha (1)-antiproteinase inactivation assay (67.2 %-92.4 % reduction when added at 1mM). Tyrosol was less active in these tests, but does not possess the catechol functionality. Despite t heir ability to interact with chemically prepared nitric oxide, neither ole uropein nor hydroxytyrosol at 5 muM altered NO. -mediated relaxations of th e nerve-stimulated rat anococcygeus preparation, but this may be because th e nitrergic transmitter is protected from the effects of externally applied scavengers. In conclusion, the phenolics found in virgin olive oil possess ability to scavenge reactive oxygen and nitrogen species that are implicat ed in human pathologies, but their impact may be restricted to those specie s present in the extracellular environment. (C) 2001 Elsevier Science Inc. All rights reserved.