Flavonol myricetin

There are several mechanisms involved in the vasodilator effect of flavonoids. The main mechanism seems to be related to the inhibition of protein kinase C or some of the processes activated by this protein. The inhibition of other protein kinases and cyclic nucleotide phosphodiesterase activity and blockage of calcium entry can also contribute to this effect to a greater or lesser extent (Alvarez Castro and Orallo, 2003 Herrera and others 1996). Certain flavonoids, like the flavonol myricetin, have a two-phase action on blood vessels vasoconstrictor in lowest active concentrations and vasodilator in higher concentrations (Alvarez Castro and Orallo, 2003). 

Vuorinen, H., Maatta, K. and Torronen, R. (2000) Content of the flavonols myricetin, quercetin, and kaempferol in Finnish berry wines, /. Agric. Food Chem., 48(7),... 

Flavonoids Flavonols Myricetin Quercetin Kaempferol Isorhamnetin Apples, apricots, grapes, plums, bilberries, cranberries, olive, elderberries, currants, cherries, blackberries, and blueberries [10]... 

FIGURE 13.5 Structures of the increasingly polar flavonols kaempferol, quercetin, and myricetin. 

Effects of Allelochemlcals on ATPases. Several flavonoid compounds inhibit ATPase activity that is associated with mineral absorption. Phloretin and quercetin (100 pM) inhibited the plasma membrane ATPase Isolated from oat roots (33). The naphthoquinone juglone was inhibitory also. However, neither ferulic acid nor salicylic acid inhibited the ATPase. Additional research has shown that even at 10 mM salicylic acid inhibits ATPase activity only 10-15% (49). This lack of activity by salicylic acid was substantiated with the plasma membrane ATPase Isolated from Neurospora crassa (50) however, the flavonols fisetln, morin, myricetin, quercetin, and rutin were inhibitory to the Neurospora ATPase. Flavonoids inhibited the transport ATPases of several animal systems also (51-53). Thus, it appears that flavonoids but not phenolic acids might affect mineral transport by inhibiting ATPase enzymes. 

Flavonols Quercetin, kaempferol, myricetin, isorhamnetin, Apples, berries, broccoli, cabbages, chives, cranberries, grapes, kale, onions, peppers, spinach, Swiss chard, tomatoes, watercress... 

Jimenez M and Garcia-Carmona F. 1999. Myricetin, an antioxidant flavonol, is a substrate of polyphenol oxidase. J Sci Food Agric 79(14) 1993-2000. 

Fig. 2.67. A typical chromatogram of flavonols in tea leaves. The chromatographic conditions are described in the text. 1 = myricetin 2 = quercetin 3 = kaempferol. Reprinted with permission from. H. Wang et al. [182],...

Quercetin is the most common flavonol in fruits, elderberries (17.0 mg/100 g), lingonber-ries (12.6 mg/100 g), and cranberries (13.0 mg/100 g) being particularly rich sources. Berries and currants are also the fruits containing most kaempferol and myricetin. For example, these two flavonols account for 29 and 18%, respectively, of the total flavonol content of the bilberry. Although kaempferol and myricetin have also been identified in fruits such as peaches and pears, concentrations are generally too low to be readily quantified in the whole fruit. The skin of these fruits contains these flavonols in significant amounts however, their flesh, which constitutes >70% of the fresh weight, does not. Consequently, when analyzed as normally eaten only trace levels are present. 

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