Flavonoids biological activities

Key Word Index - glycoside Citrus fruit biological activity flavonoid glycoside phenylpropanoid glycoside. 

Many plant extracts contain a complex mixture of flavonoids, some of which might contribute directly to particular biological properties of the extract, such as antioxidant, free radical scavenging, or estrogenic activity. The isolation of individual biologically active flavonoids from a complex mixture requires a systematic approach involving a carefully considered selection of solvents and chromatographic stationary supports. 

Bioflavonoids, also known as vitamin P (the permeabihty vitamin) are a group of biologically active flavonoids (flavonol and... 

Flavonoids are the class of plant polyqthenols with a wide spectrum of biological activities. Flavonoids protect plants against different kinds of stress. They act as a UV-filter, function as a signal molecules, antimicrobial defensive compounds, etc. [8]. 

Havonoids have a benzopyranone-ring system at their core, and a number of solid-phase and combinatorial approaches have been explored to synthesize and introduce diversity to this scaffold (such approaches have been reviewed ) with the aim of discovering novel biologically active flavonoids, flavones, and other related compounds. As with other natural products discussed herein, stmetures can be built up on resin, or preformed scaffolds can be loaded and modified... 

HARDWICK W F, KALYANARAMAN B, PRITSOS C A and PARDINI R S (1988) The production of hydroxyl and semiquinone free radicals during the autoxidation of redox active flavonoids, in Simic MG, Taylor K A, Ward J F and von Sonntag C Oxygen Radicals in Biology and Medicine, Plenum Press, New York, 149-52. 

These structurally diverse compounds exhibit a range of biological activities in vitro that may explain their potential health-promoting properties, including antioxidant and anti-inflammatory effects and the induction of apoptosis (Hooper and others 2008). Most of the recent interest in flavonoids as health-promoting compounds is related to their powerful antioxidant properties. The criteria to establish the antioxidant capacity of these compounds is based on several structural characteristics that include (a) the presence of o-dihydroxyl substituents in the B-ring (b) a double bond between positions 2 and 3 and (c) hydroxyl groups in positions 3 and 5. 

Flavonoids in general are extensively metabolized by enterocyte and hepatic cell enzymes and by intestinal microflora. Therefore, it is necessary to explore the biological activity of flavonoids and their metabolites in specific tissues, because the metabolites found in the blood flow or any specific organ may differ among themselves and from... 

Li J and Jiang Y. 2007. Litchi flavonoids isolation, identification and biological activity. Molecules 12(4) 745-758. 

Similarly to carotenoids, flavonoids also show considerable biological activity. Their beneficial effect in cancer and heart diseases has been proven many times [86-89], It has further been established that flavonoids improve cardiovascular remodelling and vascular function in NO-deficient hypertension [90], Moreover, flavonoid intake reduces the risk of chronic diseases [91], and beneficially influences inflammations [92], and ulcer formation [93,94],... 

Besides the great pigment classes such as carotenoids, flavonoids, anthocyanins and chlorophylls a wide variety of other pigments have been separated, quantitated and identified by different liquid chromatograpchic techniques. The chemical structures of these pigments show high diversity. Unfortunately, in the majority of cases the biological activity of these... 

The biological activity of flavonoids has attracted much interest in the part twenty years and a few compounds of this class have been shown to have AChEI effects. The flavanone naringenin (74) from Citrus junos (Rutaceae) ameliorated scopolamine-induced amnesia in mice, which may be related to an antiAChE effect, since naringenin was shown to inhibit AChE in vitro dose dependently. A recent theoretical study has shown that flavonoids and xanthones exhibit polyvalent effects such as antioxidant, amyloid reduction and cholinesterase inhibition, which made them interesting candidates for further studies. 

The structures used for the alkaloids in this chapter are numbered conventionally for the flavonoid or noreugenin moiety. The carbon atoms of the nitrogen-containing ring are numbered separately T, 2, etc. These alkaloids are of interest due to their amphoteric nature, being both bases and phenols, and also because of the reputed biological activity of some of the plants which contain them. 

Supramolecnlar derivatives containing crown ether [228], calixarenes [264, 265] or dendrimers [267, 279] have been synthesized with the precursors shown in Table 4.10. Fullerene-flavonoid [268] or the fuUerene glycoconjugate [258] derived from 237 and 235, respectively, are expected to show biological activity. 

Many constituents with potential biological activity have been extracted from the flowers and leaves, the parts of the plant used for medicinal purposes. These include naphthodianthrones, flavonoids, phlorogluci-nols, and xanthones. Hypericin, one of the naphthodianthrones, has traditionally been considered the main active ingredient, but it is not known whether this is the compound with antidepressant activity. Recent data suggest that a component called hyperforin may be more important than hypericin for the antidepressant activity. 

Andersen, 0.M. et al., Chive, a specialised flavonoid producer in Biologically-Active Phytochemicals in Food, Special publication — Royal Society of Chemistry, 269, 171, 2001. 

Miksicek RJ. Estrogenic flavonoids. Structural requirements for biological activity. Proc. Soc. Exp. Biol. Med. 208, 44-50, 1995. 

Hodek, P., Trefil, P., and Stiborova, M., Flavonoids potent and versatile biologically active compounds interacting with cytochromes P450, Chem. Biol. Interact., 139, 1, 2002. 

Karton, Y. et al.. Synthesis and biological activities of flavonoid derivatives as adenosine receptor antagonists, J. Med. Chem., 39, 2293, 1996. 

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