background tyrosinase is a copper-containing enzyme, which is widely distributed in microorganisms, animals and plants. it is also a key enzyme in melanin biosynthesis, which plays a crucial role in determining the color of mammalian skin and hair. in addition, unfavorable enzymatic browning of plant-derived foods by tyrosinase causes a decrease in nutritional quality and economic loss of food ...

Some intervention studies have shown that quercetin supplementation can regulate certain biomarkers, but it is not clear how the doses given relate to dietary quercetin (e.g. from onion). We conducted a two-period, two-sequence crossover study to compare the bioavailability of quercetin when administered in the form of a fresh red onion meal (naturally glycosylated quercetin) or dietary supplem...

This study proposes to investigate quercetin antitumor efficacy in vitro and in vivo, using the P39 cell line as a model. The experimental design comprised leukemic cells or xenografts of P39 cells, treated in vitro or in vivo, respectively, with quercetin; apoptosis, cell-cycle and autophagy activation were then evaluated. Quercetin caused pronounced apoptosis in P39 leukemia cells, followed b...

Epidemiological data suggest that those who consume a diet rich in quercetin-containing foods may have a reduced risk of CVD. Furthermore, in vitro and ex vivo studies have observed the inhibition of collagen-induced platelet activation by quercetin. The aim of the present study was to investigate the possible inhibitory effects of quercetin ingestion from a dietary source on collagen-stimulate...

were isolated from the roots of Verbascum lasianthum Boiss. ex Bentham. In addition, 2 phenylethanoid glycosides, verbascoside {=acteoside, [β-(3,4-dihydroxyphenyl)-ethyl]-(3′-O-α-L-rhamnopyranosyl)-(4′ O-caffeoyl)-β-D-glucopyranoside} (4) and poliumoside {= [β-(3,4-dihydroxyphenyl)-ethyl]-(3′,6′-O-αL-dirhamnopyranosyl)-(4′ -O-caffeoyl)-β-D-glucopyranoside} (5), were also isolated. The structur...

PURPOSE Quercetin is a potent chemotherapeutic drug. Clinical trials exploring different schedules of administration of quercetin have been hampered by its extreme water insolubility. To overcome this limitation, this study is aimed to develop liposomal quercetin and investigate its distribution in vivo and antitumor efficacy in vivo and in vitro. EXPERIMENTAL DESIGN Quercetin was encapsulate...

12 Some intervention studies have shown that quercetin supplementation can regulate certain biomarkers, 13 but it is not clear how the doses given relate to dietary quercetin (e.g. from onion). We conducted a 14 two-period, two-sequence crossover study to compare the bioavailability of quercetin when 15 administered in the form of fresh red onion meal (naturally glycosylated quercetin) or dieta...

Chronic inflammation in adipose tissue may contribute to depot-specific adipose tissue expansion, leading to obesity and insulin resistance. Dietary supplementation with quercetin or botanical extracts containing quercetin attenuates high fat diet (HFD)-induced obesity and insulin resistance and decreases inflammation. Here, we determined the effects of quercetin and red onion extract (ROE) con...

Understanding the cellular effects of flavonoid metabolites is important for predicting which dietary flavonoids might be most beneficial in vivo. Here we investigate the bioactivity in dermal fibroblasts of the major reported in vivo metabolites of quercetin, i.e. 3'-O-methyl quercetin, 4'-O-methyl quercetin and quercetin 7-O-beta-D-glucuronide, relative to that of quercetin, in terms of their...

BACKGROUND Part of quercetin flows into the colon after escaping the absorption of the small intestine and will be degraded by colonic microbiota. The catabolites in the colon partially determine the physiological activity of quercetin. METHODS Seven gut bacteria isolated from human feces were utilized to in vitro ferment quercetin. Their catabolites were analyzed with high-performance liquid...