title: Evaluation of a method to quantify quercetin aglycone in onion (Allium cepa) by single- and multi-laboratory validation studies.
abstract: Official Methods of Analysis of AOAC International (OMA) 2006.07 was originally designed for quantifying flavonol aglycones in ginkgo dietary supplements.  To determine whether the method is applicable to the quantification of flavonol aglycones in lyophilized onion samples, single- and multi-laboratory validation studies were performed.  Triplicated measurements on 3 different days revealed that the mean quercetin content was 3.48 g/kg dry weight, and the relative repeatability standard deviation (RSD(r)) and the relative intermediate standard deviation (RSD(int)) were 0.8 and 1.8%, respectively.  The recovery of quercetin-3-O-glucoside spiked at 3 different amounts (1.56, 3.12, and 6.24 g/kg dry weight of onion) ranged from 98.42 to 100.31%, and the RSD(r) and RSD(int) ranged from 2.2 to 5.9%, and from 3.4 to 5.2%, respectively.  A multi-laboratory validation study showed that the mean quercetin contents were 2.80 and 6.61 g/kg dry weight, and that satisfactory inter-laboratory precision (RSD(r) and RSD(R) ranged from 0.41 to 0.92%, and from 6.73 to 7.62%, respectively); all HorRat values were less than 2.  These results indicate that OMA 2006.07 is applicable to the determination of the quercetin content of lyophilized onion samples.
authors.affiliation: National Food Research Institute, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305–8642, Japan. nabej@affrc.go.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Watanabe
authors.forename: Jun
authors.initials: J
authors.lastname: Takebayashi
authors.forename: Yuko
authors.initials: Y
authors.lastname: Takano-Ishikawa
authors.forename: Akemi
authors.initials: A
authors.lastname: Yasui
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D007753:Laboratories / Q000592:standards*; D019697:Onions / Q000737:chemistry* / Q000592:standards; D011794:Quercetin / Q000032:analysis* / Q000592:standards
chemical_list: D011794:Quercetin