title: Stability and transformation of major flavonols in onion (Allium cepa) solid wastes.
abstract: Onion solid wastes were analysed using HPLC and LC / MS and the major polyphenols detected were quercetin, quercetin 4'-O-glucoside, accompanied by protocatechuic acid and a benzofuranone derivative. The latter two compounds have been demonstrated as some of the degradation products that might arise as a result of peroxidase-mediated decomposition of quercetin. These four substances, along with two principal enzymes implicated in flavonols breakdown, β-glycosidase and peroxidise, were monitored throughout an examination period of 48 h, in ground onion solid waste. The determinations showed that quercetin 4'-O-glucoside content increased by 13.3%, while quercetin, benzofuranone derivative and protocatechuic acid contents increased by 68.6, 37.5 and 58.4%, respectively. β-Glycosidase activity exhibited fluctuations and increased by 38.2%, whereas the POD showed a constant increasing trend, leading in 21.7% higher activity. On such a ground, a hypothesis was set up to explain transformations of flavonols.
authors.affiliation: Food Quality & Chemistry of Natural Products Programme, Mediterranean Agronomic Institute of Chania (M. A. I. Ch.), P. O. Box 85, 73100 Chania, Greece.
authors.forename: Zied
authors.initials: Z
authors.lastname: Khiari
authors.forename: Dimitris P
authors.initials: DP
authors.lastname: Makris
keywords: Food wastes; Onion; Oxidation; Phenolics; Quercetin
references.citation: J Agric Food Chem. 2005 Oct 19;53(21):8183-9
references.pmid: 16218662
references.citation: J Agric Food Chem. 2007 Dec 12;55(25):10067-80
references.pmid: 17997520
references.citation: Plant Cell Physiol. 2000 Sep;41(9):1021-9
references.pmid: 11100774
references.citation: Anal Biochem. 1976 May 7;72:248-54
references.pmid: 942051
references.citation: J Agric Food Chem. 2006 May 17;54(10):3551-7
references.pmid: 19127724
references.citation: J Physiol Pharmacol. 2005 Mar;56 Suppl 1:183-97
references.pmid: 15800394
references.citation: J Nutr Sci Vitaminol (Tokyo). 2007 Feb;53(1):21-9
references.pmid: 17484375
references.citation: Phytother Res. 2002 Nov;16(7):603-15
references.pmid: 12410539
references.citation: Food Chem. 2008 Jun 1;108(3):907-16
references.pmid: 26065752
references.citation: J Chromatogr A. 2006 Apr 21;1112(1-2):3-22
references.pmid: 16388813
references.citation: J Food Sci Technol. 2010 Jan;47(1):55-60
references.pmid: 23572601
references.citation: J Food Sci. 2010 May;75(4):C383-92
references.pmid: 20546399