3 -Methyl quercetin

COMT methylates quercetin to form isorhamnetin and tamarixetin, but quercetin can inhibit COMT methylation of catechol estrogens in human liver and mammary cells102-103 as well as hamster liver and kidney cells.104 In contrast to an acute dose, consumption of quercetin for 10 days by rats altered the position of methylation, as tamarixetin was undetected in the circulation.92... 

Figure 4 The conversion of quercetin to isorhamnetin (3 -0-methyl quercetin) in the whole rat lens. Lenses were incubated in 10 pM quercetin, and flavonoid content was analyzed hy HPLC. Inserts show chromatogram peaks for quercetin (first peak, retention time 19 min) and isorhamnetin (second peak, retention time 21 min) at (A) 1...

Figure 5 Dose-dependent inhibition of the conversion of quercetin to isorhamnetin (3 -0-methyl quercetin) by the catechol-0-methyl transferase inhibitor 3, 5-...

One point should be raised that was not dealt with in the Lauranson and Lebreton (1991) paper. It would appear that the authors examined the concentration values of the individual flavonols at face value without considering likely or possible biosynthetic relationships. In particular, isorhamnetin is produced by 0-methylation of quercetin. Total quercetin produced would then be the sum of quercetin per se plus the amount of isorhamnetin present. This value, reflecting total 3, 4 -dioxygenated flavonols, would be the more accurate measure of allele frequency. 

Harborne, J. B. and Davenport, S. M. 1966. Identification of quercetin 5-methyl ether... 

PEDRiELLi p and SKIBSTED L H (2002) Antioxidant syneigy and regeneration effect of quercetin, (-)epicatechin, and (+)-catechin on a-tocopherol in homogeneous solutions of peroxidating methyl linoleate, JAgric Food Chem, 50, 7138-44. 

PEDRIELLI p, PEDULLi G F and SKIBSTED L H (2001a) Antioxidant mechanism of flavonoids. Solvent effect on rate constant for chain-braining reaction of quercetin and epicatechin in autoxidation of methyl linoleate, JAgric Food Chem, 49, 3034-40. 

The plant is known elaborate a series of quite unusual phenanthrene alkaloid derivatives, of which aristoliukine-C, aristofolin A and E, aristolochic acid-la methyl ester, and aristolochic acid. Other chemical constituents found in this plant are flavonoid glycosides such as kaempferol-3-O-rutinoside and quercetin kaempferol-3-O-rutinoside (3,4). Exposure to Aristolochiaceae family is associated with the development of cancer in humans. A significant advance is the toxicological effects of aristolochic acid has been provided by the work of Pezzuto et al. They showed that aristolochic acid is a mutagen... 

An extract from Lactuca indica showed significant free radical scavenging activity, and protected phixl74 supercoiled DNA against strand cleavage and reduced oxidative stress in human promyelocytic leukemia HL-60 cells. On account of protocatechulic acid, methyl p-hydroxybenzoate, caffeic acid, 3,5-dicaffeoylquinic acid, luteolin 7-O-fT glucopyranoside, and quercetin 3-0-(3-g 1 ucopyranoside are the major antioxidative constituents (111). 

Flavonoids bonded to fibres undergo photodegradation over the course of time their identification in historic textiles is thus often difficult. The analysis of a wool orange fibre (from a nineteenth century Aubusson tapestry) dyed with alum mordant and quercetin enabled the presence of quercetin (at m/z 301) and its decomposition products, 3,4-dihydroxybenzoic acid (at m/z 153) and methyl 3,4-dihydroxybenzoate (at m/z 167), to be confirmed. [30] The samples were hydrolysed with hydrochloric acid and analysed with RPLC MS. 

Flaveria haumanii, Cotinus coggygria, Coreopsis spp. and pre Columbian Andean textiles Okanine, luteolin, butein (as aglycones, glycosides or as methyl ethers), quercetin, isorhamnetin (as sulfate esters), sulfuretin, fisetin, hydroxybenzoic acids HCI/Me0H/H20, HCOOH/MeOH A H20 B ACN C H20 with HCOOH 254, 350 nm/ESI (+) Column C4 7... 

Compounds 1 = 4-hydroxycoumarin 2 = umbelliferon 3 = 4-methyl-esculetin 4 = isopimpinellin 5 = esculin 6 = flavone 7 = a-naphtoflavone 8 = kaempferol 9 = quercetin 10 = isoquercitrin 11 = robinetin 12 = robinin 13 = myricetin 14 = luteolin 7-O-glucoside 15 = rutin 16 = hes-peretin 17 = hespiridin 18 = naringin 19 = pelargonin chloride 20 = polargonin chloride 21 = malvin chloride. 

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