Quercetin catechin and

Morel et al. (1993) have reported that three flavanoids (catechin, quercetin and diosmetin) are cytoprotective on iron-loaded hepatocyte cultures. Their cytoprotective activity (catechin > quercetin > diosmetin) correlated with their iron-chelating ability (Morel et al., 1993). These compounds should also be good phenolic antioxidants so iron chelation may only be part of the story. 

Morel, I., Lescoat, G., Cogrel, P., Sergent, O., Pasdeloup, N., Brissot, P., Cillard, P. and Cillard, J. (1993). Antioxidant and iron chelating activities of the flavonoids catechin, quercetin and diosmetin on iron-loaded rat hepatocyte cultures. Biochem. Pharmacol. 45, 13-19. 

Auger C, Teissedre PL, Gerain P, Lequeux N, Bomet A, Serisier S, Besancon P, Caporiccio B, Cristol JP, Rouanet JM. 2005. Dietary wine phenolics catechin, quercetin, and resveratrol efficiently protect hypercholesterolemic hamsters against aortic fatty streak accumulation. J Agric Food Chem 53 2015-2021. 

Soleas GJ, Yan J, Goldberg DM. 2001b. Ultrasensitive assay for three polyphenols (catechin, quercetin and resveratrol) and their conjugates in biological fluids utilizing gas chromatography with mass selective detection. J Chromatogr B Biomed Sci Appl 757 161-172. 

Afanas ev et al. demonstrated the ability of rutin to form a stable complex with Fe2+ at physiological pH [142]. The absorption spectrum of the Fe2+-rutin complex did not change during 8 hours [142]. Morel et al. investigated radiochemically the capacity of three flavonoids (catechin, quercetin and diosmetin) and desferrioxamine - a powerful chelator of Fe3+ - to remove Fe3+ from iron-loaded hepatocytes [18, 143]. Nitrilotriacetic acid - a low affinity iron-chelator - was used to maintain Fe3+ in a soluble state. The iron-chelating ability decreased in the following order desferrioxamine > catechin > quercetin > diosmetin (which had a very low activity) [18, 143]. 

In the 70s and 80s, balance studies with radioactively labelled flavonoids were performed to quantify the rate of absorption of different compounds including catechins, quercetin and flavanones (aglycones in all cases) in different mammals including man. Different absorption rates were detected depending on the flavonoid type. Thus, catechin was well absorbed since 47% to 58% of the administered radioactivity was excreted in urine. Quercetin was less well absorbed than catechins and only 4-13% of the administered radioactivity was recovered with urine, while around 40% was excreted with faeces. The absorption of flavanones was higher with 30% being excreted with urine [137]. 

Absorption of trans-resveratrol and other related compounds in rats was investigated [36]. Male Wistar rats (350 g) were used in a bioavailability study of [ H]trans-resveratrol administered by gavage together with (+ )-catechin, quercetin, and unlabeled trans-resveratrol in matrices of 10% ethanol, V8 vegetable homogenate mixture, and white grape juice. Whole blood, blood serum, urine, feces, and tissue... 

Unnikrishnan et al. [100] reported the fabrication of a selective voltammetric sensor for the determination of chlorpromazine (an antipsychotic drug) using GCE modified with MWCNT-PEI, in the presence of uric acid (UA), Do, and acetaminophen. The GCE/MWCNT-PEI platform was also employed for the quantification in batch of flavonoid compounds in onion samples [135] and peanut hull samples [136], and as a detector in capillary electrophoresis, for the simultaneous detection of eight polyphenols (t-resveratrol, (-i-)-catechin, quercetin and /)-coumaric, caffeic, sinapic, ferulic, and gallic acids) in Spanish white wines [137]. 

Table 10.14. Effect of catechins, quercetin and a-tocopherol on the oxidation of phosphatidylcholine (PC) liposomes or solutions initiated by AAPH ...

Hamameli tannin, gallotannins (>12) catechins, quercetin, and kaempferol glycosides... 

As a result of the low concentration of flavanols in blood fractions such as plasma when food level doses are consumed, there are only a few techniques that have sufficient sensitivity. The first of these is gas chromatography coupled to a mass spectrometer for detection [88]. This technique is quite sensitive and provides the assurance of accurate identification of the analyte when the molecular and major fragmentation ions are monitored. The drawbacks are that it is necessary to derivatize the flavanols to achieve sufficient volatility and the technique cannot be adapted for analysis of glucuronide and sulfate conjugates. This method has been used to quantify the plasma levels of catechin and its methylated derivatives after wine consumption, and a modified version is able to detect catechin, quercetin, and resveratrol simultaneously [89]. 

The chemical formulae for a variety of plant phenols are given in Fig. 16.2, including examples of simpler phenols, such as cinnamic acid derivative, and of tocopherols, flavonoids, flavonoid glycosides and anthocyanidins. The flavonoids include the following subclasses flavanones (taxifolin), flavones (luteolin), flavonols (quercetin) and flavanols (catechin/epicatechin). The... 

Red wine contains quercetin, rutin, catechin, and epicatechin, among other flavonoids (Frankel and others 1993). Quercetin and other phenolic compounds isolated from wines were found to be more effective than a-tocopherol in inhibiting copper-catalyzed LDL oxidation. It has been determined that quercetin has also several anti-inflammatory effects it inhibits inflammatory cytokine production (Boots and others 2008), inducible NO synthase expression and activation of inflammatory transcription factors (Hamalainen and others 2007), and activity of cyclooxygenase and lipooxygenase (Issa 2006), among others. 

The effects of flavonoids on in vitro and in vivo lipid peroxidation have been thoroughly studied [123]. Torel et al. [124] found that the inhibitory effects of flavonoids on autoxidation of linoleic acid increased in the order fustin < catechin < quercetin < rutin = luteolin < kaempferol < morin. Robak and Gryglewski [109] determined /50 values for the inhibition of ascorbate-stimulated lipid peroxidation of boiled rat liver microsomes. All the flavonoids studied were very effective inhibitors of lipid peroxidation in model system, with I50 values changing from 1.4 pmol l-1 for myricetin to 71.9 pmol I 1 for rutin. However, as seen below, these /50 values differed significantly from those determined in other in vitro systems. Terao et al. [125] described the protective effect of epicatechin, epicatechin gallate, and quercetin on lipid peroxidation of phospholipid bilayers. 

Numerous studies were dedicated to the effects of flavonoids on microsomal and mitochondrial lipid peroxidation. Kaempferol, quercetin, 7,8-dihydroxyflavone and D-catechin inhibited lipid peroxidation of light mitochondrial fraction from the rat liver initiated by the xanthine oxidase system [126]. Catechin, rutin, and naringin inhibited microsomal lipid peroxidation, xanthine oxidase activity, and DNA cleavage [127]. Myricetin inhibited ferric nitrilotriacetate-induced DNA oxidation and lipid peroxidation in primary rat hepatocyte cultures and activated DNA repair process [128]. 

Flavonoids exhibit protective action against LDL oxidation. It has been shown [145] that the pretreatment of macrophages and endothelial cells with tea flavonoids such as theaflavin digallate diminished cell-mediated LDL oxidation probably due to the interaction with superoxide and the chelation of iron ions. Quercetin and epicatechin inhibited LDL oxidation catalyzed by mammalian 15-lipoxygenase, and are much more effective antioxidants than ascorbic acid and a-tocopherol [146], Luteolin, rutin, quercetin, and catechin suppressed copper-stimulated LDL oxidation and protected endogenous urate from oxidative degradation [147]. Quercetin was also able to suppress peroxynitrite-induced oxidative modification of LDL [148],... 

Another study employed a similar RP-HPLC method for the determination of trails- and d.v-rcsvcratrol, catechin, epicatechin, quercetin and rutin in wines and musts. Wine samples were filtered and diluted when necessary and used for analysis without any other pretreatment. Separation was performed in an ODS column (150 X 4 mm i.d. paricle size 5 71m) at ambient temperature. The gradient began with ACN-5 per cent aqueous acetic acid (9 91, v/v) for 0-10 min to 25 75 in 1 min hold for 11 min to 70 30 in 1 min, hold for 5 min. The flow rate was 1 ml/min. Analytes were detected by DAD. Fluorescence detection used 280/315 nm (excitation/emission) for catechin and epicatechin 314/370 nm for fims-resveratrol and 260/370 nm for d.v-rcsvcratrol. Chromatograms of a red wine sample obtained at different... 

Fig. 2.90. Electropherograms of sterile root exudate before (a) and after incubation with Mesorhizobium loti (b) and Rhizobium leguminosarum bv. trifolii (c). From their UV spectra, peaks 1-6 were identified as resorcinol, rhamnetin, catechin, quercetin glycoside, quercetin aglycone and hesperidin. Differences in the retention times of the same compounds in different samples could be due to the variations in buffer temperature or sample composition. Reprinted with permission from H. L. Steele et al. [213].

Fruit juice contains both catechins and flavonols. Apple juice is one of the richest juice sources of catechins (containing 6.3 mg (—)-epicatechin/100 ml and 0.8 mg (+)-catechin/ 100 ml) whereas cranberry juice contains the most flavonols, mainly in the form of quercetin and myricetin (17.5 mg/100 ml and 4.7 mg/100 ml, respectively). 

The flavonoid content of plant foods may be affected by growing conditions.For example, red wine produced in the warm, dry, and sunny conditions prevalent in the New World tend to contain more quercetin and myricetin (but less catechin) than the wines produced in the cooler and damper regions of Northern Europe.Similar regional and climatic effects on... 

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