Flavanoid

FIa.VOnoIOxida.tlon, The fermentation process is initiated by the oxidation of catechins (1) to reactive catechin quinones (13), a process catalyzed by the enzyme polyphenol oxidase (PPO) (56). Whereas the gaHocatechins, epigaHocatechin, and epigaHocatechin gaHate, are preferred, polyphenol oxidase can use any catechin (Table 2) as a substrate. This reaction is energy-dependent and is the basis of the series of reactions between flavanoids that form the complex polyphenoHc constituents found in black and oolong teas. 

Catechin and epicatechin are two flavanols of the catechin family. They are enantiomers. The capillary zone electrophoresis (CE) methods with UV-detection were developed for quantitative determination of this flavanols in green tea extracts. For this purpose following conditions were varied mnning buffers, pH and concentration of chiral additive (P-cyclodextrin was chosen as a chiral selector). Borate buffers improve selectivity of separation because borate can make complexes with ortho-dihydroxy groups on the flavanoid nucleus. 

Polyphenols and flavanoids in rat liver microsomal fractions have been demonstrated to inhibit glucuronidation of estrone and estradiol in vitro (Zhu et al, 1998). In addition, flavonoids have also been found to induce phase I and II enzymes in rats including UDP-glucuronosyl transferase (Seiss et al, 1996). However, the effects of phytoestrogens have not been evaluated for either their inhibition or induction of glucuronosyl transferase activity. 

Important reductions are involved in the anaerobic transformations of steroid and flavanoids ... 

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. 

In the case of the low abundance of some compounds, there are difficulties with signal overlap. To overcome these difficulties, there have been developments involving NMR hyphenation with techniques such as HPLC and mass spectrometry. In LC/NMR methods of analysis, NMR is used as the detector following LC separation and this technique is capable of detecting low concentrations in the nanogram range. This technique has been reported for the detection and identification of flavanoids in fruit juices and the characterization of sugars in wine [17]. 

Now that an haustorial inducing factor has been characterized in a host plant that could be grown in the laboratory, the levels of the compounds actually exuded could be analyzed. John Steffens and Rody Spivey focused on developing methods that would allow for suitable quantitation. Efforts were made to quantitate not only the terpenoid components, but also the flavanoid, genistein (4, 5,7-trihydroxyiso-flavone), which was found to be a major isoflavone of Lespedeza. Genistein was analyzed to gain an estimate of levels of phenylpro-... 

The syntheses of flavanoid alkaloids also rest on A-l-pyrroline chemistry and on Friedel-Crafts-type reactions. In Govindachari s pioneering synthesis of ficine (167), pyrrolidine 126 is formed by condensation of trimethoxybenzene and y-aminobutyric acid in the presence of PPA (Scheme 19). Although the mechanism of this reaction has not been precisely determined, it may involve a A-l-pyrrolinium cation. These conditions were later used by Koch et al. in their synthesis of vochysine (Scheme 20) (108). 

Kootstra A (1994) Protection from UV-B-induced DNA damage by flavanoids. Plant Mol Biol 26 771-774... 

Natural colours include annatto, anthocyanins, beetroot red (betalaines), caramel, carotenoids, cochineal and lac pigments, flavanoids, chlorophylls and tumeric. There is a trend towards encapsulating natural colours for food use, but this is not yet reflected in the extraction techniques described in the published analytical methods. Lancaster and Lawrence (1996) described the extraction and... 

Rahim, A.A., Rocca, E., Steinmetz, J., Adnan, R. and Kassim, M.J., 2004, Mangrove tannins as corrosion inhibitors in acidic medium-Study of flavanoid monomers. In Proceedings of the European Corrosion Conference (EUROCORR 2004), 12-16 September, Nice, Paper No. 41. 

This limitation is well Illustrated by the failure of those methods to uncover the presence of another important group, the flavanoid, coumarin and cinnamic acid phenols (85 - 117). On the other hand, some 32 of these compounds were identified when isolation procedures specific for these types of compounds were employed. Using isolation and identification techniques which are particularly useful for alkaloids, it would be possible to determine whether any representatives of this class are present and, if so, to conduct subsequent studies for structure determination. 

Biflavanoids in vegetables and fruits play a vital role in the storage of ascorbic acid in leukocytes, in the core of adrenal glands and in other organs. It also causes more effective expenses under ascorbic acid s deficiency in the organism. Phenolic compounds present in the organism, activate detoxication processes in the liver. The flavanoids exceed the tocopherols and carotenoids in terms of antioxidant effect. 

Building blocks Gallic acid, galloyl ester, ester-linked with glucose Flavanoid units (Procyanidins), catechin... 

This specificity seemed quite remarkable since Agalinis parasitizes a broad spectrum of hosts. Nevertheless, flavanoids and phenolics have frequently been cited as playing a role in allelopathy (15). Xenognosin A has also been found in Pisum as a... 

---