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 e… Show more
“…Figure 1 illustrates the structures of quercetin aglycone, which lacks a sugar moiety, and of quercetin-β-glucoside, which has been reported to be contained mainly in onions. 14 , 15 Figure 1 Structure of quercetin aglycon ( A ), and quercetin-4ʹ-O-β-D-glucoside ( B ). …”
Section: Chemical Structure and Dietary Source Of Quercetinmentioning
Obesity has become a major risk factor for the development of chronic diseases such as insulin resistance, type 2 diabetes mellitus, and cardiovascular disease. Moreover, obesity induces chronic inflammation in adipose tissue, liver, skeletal muscle, and the vascular system. Quercetin is the major representative of the flavonoid subclass of flavonols, which is ubiquitously contained within natural plants such as green tea, and vegetables, including onions and apples. Researchers have focused greater attention to the beneficial physiological roles of quercetin, which has anti-oxidative, anti-inflammatory, and anti-fibrotic effects on insulin resistance and atherosclerosis in obesity-related diseases. Also, the anti-inflammatory effects of quercetin on intestinal microbiota have been demonstrated in obesity. In addition, there is increasing evidence that quercetin is associated with epigenetic activities in cancer, and in maternal undernutrition during gestation and lactation. In this review, we focus on the chemical properties of quercetin, its dietary sources in obesity, and its anti-inflammatory effects on insulin resistance, atherosclerosis, intestinal microbiota, and maternal under-nutrition with epigenetic activity.
“…Figure 1 illustrates the structures of quercetin aglycone, which lacks a sugar moiety, and of quercetin-β-glucoside, which has been reported to be contained mainly in onions. 14 , 15 Figure 1 Structure of quercetin aglycon ( A ), and quercetin-4ʹ-O-β-D-glucoside ( B ). …”
Section: Chemical Structure and Dietary Source Of Quercetinmentioning
Obesity has become a major risk factor for the development of chronic diseases such as insulin resistance, type 2 diabetes mellitus, and cardiovascular disease. Moreover, obesity induces chronic inflammation in adipose tissue, liver, skeletal muscle, and the vascular system. Quercetin is the major representative of the flavonoid subclass of flavonols, which is ubiquitously contained within natural plants such as green tea, and vegetables, including onions and apples. Researchers have focused greater attention to the beneficial physiological roles of quercetin, which has anti-oxidative, anti-inflammatory, and anti-fibrotic effects on insulin resistance and atherosclerosis in obesity-related diseases. Also, the anti-inflammatory effects of quercetin on intestinal microbiota have been demonstrated in obesity. In addition, there is increasing evidence that quercetin is associated with epigenetic activities in cancer, and in maternal undernutrition during gestation and lactation. In this review, we focus on the chemical properties of quercetin, its dietary sources in obesity, and its anti-inflammatory effects on insulin resistance, atherosclerosis, intestinal microbiota, and maternal under-nutrition with epigenetic activity.
“…The outer dry layers of onion bulbs contain a peculiar variety of polyphenols, many of them considered to derive from quercetin and quercetin glucosides, upon the action of peroxidase (LY et al, 2005;RAMOS et al, 2006;KHIARI & MAKRIS, 2012). The chromatogram of the extract obtained at 40 °C, which was monitored at 290 nm, revealed the presence of 5 major peaks accompanied by several minor substances.…”
Previous reports highlighted the onion solid wastes as abundant, residual material that might contain a signifi cant load of antioxidant polyphenols. Although there have been studies pertaining to polyphenol recovery from onion wastes, the effect of temperature has not been adequately addressed. In this line, this study was undertaken with the aim of establishing a correlation between the extraction yield in total polyphenols and the extraction temperature, using acidifi ed aqueous ethanol as the solvent system. Extraction of polyphenols from onion solid wastes was found to obey 2 nd -order kinetics. On such a basis, the yield in total polyphenols at saturation could be very effectively determined and correlated with temperature using non-linear regression. The results indicated that the extraction yield at saturation is highly correlated with temperature, following a quadratic function. The extract obtained at optimal temperature (40 °C) had a total polyphenol yield of 21.10 mg gallic acid equivalents per gram of dry weight, and it was further analysed by liquid chromatography-mass spectroscopy to characterise its major constituents. The polyphenols detected were quercetin glucosides, as well as quercetin oxidation derivatives, including certain degradation products and dimers. The outcome of this study outlined that temperatures above 40 °C are rather not favourable for polyphenol extraction from onion solid wastes, as suggested by the model established through kinetics. The extract obtained under optimal conditions contained peculiar polyphenolic composition, not encountered in any other food processing residue.
“…Among others, the dried outer skin of onions ( Allium cepa L.), representing the waste of onion consumption and processing, contains a multitude of colored bioactive phenolics, some of which are absent in the edible part of the vegetable [15,16,17]. In depth investigations at a molecular level have revealed that quercetin and its glucosides are the most abundant phenolics in onion outer dry layers, which explains the strong antioxidant effects of the resulting extracts [18,19,20].…”
The aqueous extract of dry onion skin waste from the ‘Dorata di Parma’ cultivar was tested as a new source of biomolecules for the production of colored and biofunctional wool yarns, through environmentally friendly dyeing procedures. Specific attention was paid to the antioxidant and UV protection properties of the resulting textiles. On the basis of spectrophotometric and mass spectrometry analyses, the obtained deep red-brown color was assigned to quercetin and its glycoside derivatives. The Folin–Ciocalteu method revealed good phenol uptakes on the wool fiber (higher than 27% for the textile after the first dyeing cycle), with respect to the original total content estimated in the water extract (78.50 ± 2.49 mg equivalent gallic acid/g onion skin). The manufactured materials showed remarkable antioxidant activity and ability to protect human skin against lipid peroxidation following UV radiation: 7.65 ± 1.43 (FRAP assay) and 13.60 (ORAC assay) mg equivalent trolox/g textile; lipid peroxidation inhibition up to 89.37%. This photoprotective and antioxidant activity were therefore ascribed to the polyphenol pool contained in the outer dried gold skins of onion. It is worth noting that citofluorimetric analysis demonstrated that the aqueous extract does not have a significative influence on cell viability, neither is capable of inducing a proapoptotic effect.
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