title: Beetroot betalain inhibits peroxynitrite-mediated tyrosine nitration and DNA strand cleavage.
abstract: Two major betalains, red-purple betacyanins and yellow betaxanthins, were isolated from red beetroots (Beta vulgaris L.), and their peroxynitrite (ONOO(-)) scavenging capacity was investigated. Apparent colours of the betalains were bleached by the addition of ONOO(-), and the absorbance decreases were suppressed in the presence of glutathione, a ONOO(-) scavenger. After bleaching, a new absorption maximum was observed at 350 nm in the spectrum of the resulting reaction mixture. New peaks were detected from HPLC analysis of the reaction products of betanin, a representative constituent of red beetroot betacyanins, treated with ONOO(-) monitoring at 350 nm, and the intensity of the major peak was positively correlated with ONOO(-) concentration. Betanin inhibited the ONOO(-) (0.5 mM)-dependent nitration of tyrosine (0.1 mM). Additionally, the IC(50) value of betanin (19.2 μM) was lower than that of ascorbate (79.6 μM). The presence of betanin (0.05-1.0 mM) also inhibited ONOO(-) (0.5 mM)-dependent DNA strand cleavage in a concentration-dependent manner. These results suggest that betalains can protect cells from nitrosative stress in addition to protecting them from oxidative stresses.
authors.affiliation: Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan. sakihama@abs.agr.hokudai.ac.jp
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Sakihama
authors.forename: Makiko
authors.initials: M
authors.lastname: Maeda
authors.forename: Makoto
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tahara
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Hashidoko
mesh_terms: D027461:Beta vulgaris / Q000737:chemistry; D050858:Betalains / Q000302:isolation & purification / Q000494:pharmacology*; D053960:DNA Breaks; D016166:Free Radical Scavengers / Q000302:isolation & purification / Q000494:pharmacology*; D009566:Nitrates / Q000737:chemistry / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000037:antagonists & inhibitors* / Q000737:chemistry; D017382:Reactive Oxygen Species; D014443:Tyrosine / Q000031:analogs & derivatives / Q000737:chemistry* / Q000378:metabolism
chemical_list: D016166:Free Radical Scavengers; D009566:Nitrates; D017382:Reactive Oxygen Species; D030421:Peroxynitrous Acid; D050858:Betalains; D014443:Tyrosine