title: Development of a signal-ratio-based antioxidant index for assisting the identification of polyphenolic compounds by mass spectrometry.
abstract: A new concept, called the signal-ratio-based antioxidant index (SRBAI), is proposed for the identification of antioxidants. The SRBAI is derived from the signal ratio of free-radical scavenging to polyphenolic chromophore absorbance. Each SRBAI value corresponds to a specific antioxidant under the same antioxidant assay condition. Hence, the SRBAI can be used as an identification card of the antioxidant, which can resolve even components with the same retention time or with similar mass fragmentation spectra. We employed onion and several quercetin glycosides as models. There are four major peaks of onion with free-radical scavenging ability. One of the peaks failed to be identified; for the authentic compounds, quercetion-3-glucoside (SRBAI = 8.98) and quercetin-3-rutinoside (SRBAI = 3.01) eluted at the same retention time as the unknown peak. However, the unknown was considered to be quercetin-3-glucoside for its SRBAI was 8.91. SRBAI values also can be applied to differentiate the unknown peaks with the same parent ion of m/z 463 and collision-induced dissociation (CID) spectra as the two authentic compounds, quercetin-3-glucoside and quercetin-4'-glucoside. This newly introduced SRBAI can act as an efficient and precise identification tool, especially for online identification of similar polyphenolic isomers.
authors.affiliation: Department of Applied Chemistry, National Chiayi University, Chiayi City 60004, Taiwan.
authors.forename: Che-I
authors.initials: CI
authors.lastname: Liao
authors.forename: Kuo-Lung
authors.initials: KL
authors.lastname: Ku
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D059808:Polyphenols / Q000032:analysis*; D011794:Quercetin / Q000031:analogs & derivatives / Q000032:analysis; D012431:Rutin / Q000032:analysis; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000975:Antioxidants; D059808:Polyphenols; C016527:isoquercitrin; D012431:Rutin; D011794:Quercetin