Flavones absorption

Ameer, B., Weinbaub, R. A., Johnson, J., et al., Flavone absorption after naringin, hesperidin and citrus administration, Clin. Phamacol. Ther. (1996) 60(1), 34-40. 

Diphenylboric acid-2-aminoethyl ester reacts to form complexes with 3-hydroxy-flavones with bathochromic shift of their absorption maximum. 

Effects of Allelochemlcals on ATP Supply. Allelochemlcals might decrease the ATP content of tissue by either increasing ATP utilization or decreasing ATP production. Some allelochemlcals that inhibit mineral absorption decrease ATP content of plant tissues. Salicylic acid decreased the ATP content of oat roots in a pH dependent manner (Figure 3). This result suggested that mitochondrial production of ATP was decreased in the tissue. On the other hand, Tillberg (38) found that salicylic acid and cinnamic acid increased the ATP content of Scenedesmus. Various flavonoids inhibited ATP production by mitochondria Isolated from cucumber (Cucumls satlvus L.) hypocotyls (54). Flavones such as kaempferol were more inhibitory than the corresponding flavanones. Substituted cinnamic acids such as caffeic acid were not inhibitory. 

Briggs, L. and Colebrook, L., Infrared spectra of flavanones and flavones. Carbonyl and hydroxyl stretching and CH out-of-plane bending absorption, Spectrochim. Acta, 18, 939, 1962. 

Data on the absorption of flavones (namely luteolin) are limited. Shimoi... 

Electron densities and bond orders for pyran-2-one, pyran-4-one and eight benzologues or dibenzologues have been calculated using the simple Hiickel, the Hiickel autocoherent and the semi-empirical Pople methods (74BSF538). Similar properties have been obtained for flavone and the electronic absorption spectra of some substituted flavones have been examined in detail (74CHE1218). Excitation is accompanied by a transfer of charge from the... 

It is often possible to distinguish the various types of flavonoids by examination, particularly of the band I absorption. Thus, flavones (22) absorb at 300-350 nm, whilst in flavonols (111) this peak occurs in the region 350-385 nm. The general effect of hydroxy groups is bathochromic, although these effects are quite specific. Substitution in ring B leads to a red shift of band I, but leaves band II much the same. Conversely, band II is affected by substitution in ring A. 

Unlike some classes of polyphenols such as flavonols and flavones, flavanols are almost always present in the nonglycosylated form. Removal of glycoside from flavonoids, usually necessary before the transport across the intestinal barrier, is not required in the case of flavanols [Scalbert and Williamson, 2000]. The absorption of procyanidins by the small intestine was investigated by studying 14C-( + )-catechin, dimer, trimer, and procyanidin polymers permeation through Caco-2 cell cultures [Deprez et al., 2001]. There was little difference in permeability between monomer, dimmer, and trimer, based on the measurement of radioactivity present on the basal side of the cultures, whereas the permeability of the polymers was 10 times lower. The authors reported the absence of catechin metabolism but did not determine whether the radioactivity measured on the basal side of the cultures was from the parent dimers to polymers or from their products of degradation or metabolites, which could have resulted from instability of the parent compounds in the culture... 

Neohydnocarpin (80), C24H20O9, showed a UV absorption spectrum typical of a flavone. Detailed NMR spectroscopic analysis led to the proposal of the presence of a luteolin (118) and a coniferyl alcohol moiety (45). Careful examination of the C NMR spectrum showed the absence of oxygen functions at C-7" and C-8", which resonated at 35.2 and 40.9 ppm, compared to those in silybin A (89) at Sc... 

BILBERRY, Myrtilli fructus Bilberry is the fruit of Vaccinium myrtillus, L., family Ericaceae, and contains 5-10% tannins of the catechin-type, anthocyanins, flavone glycosides and organic acids. The tannins in bilberry and in other tannin-containing drugs precipitate proteins in the epithelium of the intestine. In this way the absorption of toxic substances and secretion is diminished. This is the mode of action in the treatment of diarrhoea. 

The threat of nuclear fallout from atomic weapons testing was the impetus for a large number of studies that investigated methods to prevent absorption of radiostrontium, while not adversely affecting the absorption of calcium. Reasonably effective strategies have included alginates, aluminum phosphate, and sulfates. Less effective or less practical strategies have included cold, diet, dietary fiber, flavones, and stable strontium. 

In the living cell these compounds exist in more complex bound forms, interacting with other molecules, for example flavones, and the actual observed colour depends on these interactions. However, it is interesting that even in vitro, simple pH changes bring about extreme changes in the electronic absorption of these molecules. For example cyanidin is red in acidic solution, violet at intermediate pH and blue in weakly alkaline solution, the deep colours being the result of extensive resonance delocalisation in each of the structures. 

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