Phloridzin and phloretin

In apple, the glycoside phloridzin (1.27) and its aglycone phloretin are thought to inhibit the apple scab fungus Venturia inaequalis. Phloridzin is also an ort/20-dihydroxyphenolic compound, and, like chlorogenic acid, can also be easily converted to a reactive quinone upon attack by a pathogen. Raa (1968) demonstrated that oxidation products of phloridzin inhibit fungal 

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Chalcones and dihydrochalcones have been reported in a restricted number of foods (Robards and others 1999 Tomas-Barbcran and Clifford 2000). Chalconaringenin occurs in tomato skin, but the acid extraction conditions of the usual polyphenol analyses convert the chalcone to the corresponding flavanone (naringenin) in the tomato. The most common dihydrochalcones found in foods are phloretin glucoside (phloridzin) and phloretin xylogalactoside, which are characteristic of apples (see Table 2.2) and derived products such as apple juice, cider, and pomace (Robards and others 1999 Tomas-Barbcran and Clifford 2000). 

Nelson JAS, Falk RE (1993) The efficacy of phloridzin and phloretin on tumor cell growth. Anticancer Res 13 2287... 

Mizuma T, Awazu S. Inhibitory effect of phloridzin and phloretin on glucuronidation of p-nitrophenol, acetaminophen and 1-naphthol kinetic demonstration of the influence of glucuronidation metabolism on intestinal absorption in rats. Biochim Biophys Acta 1998 1425 398-404. 

The most characteristic compounds of apple are the dihydrochalcones, analysis of which can be applied to apple-derived food characterisation (juices, jams, purges, cider, etc.). Phloretin 2 -glucoside (phloridzin) (Fig. 5) and phloretin 2 -(2"-xylosylglucoside) are the only dihydrochalcones reported in apple so far [20]. 

During degradation phloridzin is cleaved to glucose and phloretin which either... 

The occurrence of species-specific constituents is also analytically useful. The composition of the plant phenols of individual fruits can be analyzed quickly and very accurately by using HPLC. These data have shown that certain compounds are suitable indicators of adulteration (Table 18.42). These indicators must be fixed with great care. In fact, phloretin-2-glucoside (phloridzine) and isorhamnetinglucoside have been proposed as markers for apples and pears. Improvements in the analyses, however, showed that phloridzine and isorhamnetinglucoside widely occur in low concentrations in fruit, and the last mentioned glucoside also occurs in apples, among other fruit. 

Phloridzin (XXXII) is a phenolic glucoside of phloretin. When administered to animals orally or subcutaneously, both phloridzin and its aglu-cone, phloretin, give rise to an intense glycosuria without an accompanying hyperglycemia the blood-sugar level is in fact diminished and the renal... 

Fig. 2.56. HPLC chromatogram of (a) Golden peel and (b) Golden pulp extracts at 280 nm. Peaks 1 = procyanidin B3 2 = procyanidin Bl 3 = ( + )-catechin 4 = procyanin B2 5 = chlorogenic acid 6 = ( — )-epicatechin 7 = caffeic acid 8 = phloretin derivative 9 = phloridzin 10 = rutin 11, 12 and 13 = flavonol glucosides. Reprinted with permission from A. Escarpa et al. [160].

The phenolics ( + )catechin and (— )epicatechin are common flavanols in several fruits (128). Apples and pears contain other phenolic compounds such as quinic, shikimic, chlorogenic, and caffeic acids (39). Durkee and Poapst (162) reported that the two major phenolic constituents of core tissues and seeds of McIntosh apples were chlorogenic acid and phloridzin. After hydrolysis of extracts from core tissues, the identified phenolics were phloretin, caffeic acid, p-coumaric acid, phloretic acid, and trace amounts of ferulic acid. Studies have shown that apple leucoanthocyanins yield catechin, epicatechin, cyanidin, and pelargonidin after hydrolysis (163, 164). Van Buren et al. (164) also reported that a purified leucoanthocyanin from apples was either a dimer or oligomer containing ( —) epicatechin, and 5,7,3, 4 -flavin-3,4-diol. 

Chalcones, such as butein (1.26), are yellow pigments in flowers. An example of a dihydrochalcone is phloridzin (phloretin-2 -0-D-glucoside) (1.27), a compound found in apple leaves, and which has been reported to have anti-tumor activity (Nelson and Falk, 1993). 

The compound must be present in those parts of the plant where the pathogen will come in contact with it. For example, apple leaves contain phloridzin (6.1) and its aglycone phloretin (6.2), but these compounds are not present in the lfuit. 

Phloridzin (D 22.3.3) In infected apple leaves phloridzin is hydrolized to phloretin which is hydroxylated to 3-hydroxy-phloretin and oxidized to the corresponding fungitoxic o-quinone... 

The bio availability of phloretin and its glucoside phloridzin was shown to be similar in rats, except that the kinetics of absorption was delayed for phloridzin (Crespy etal. 2001). About 10% of the ingested dose was excreted in the urine in 24 h, and plasma concentrations were returned to baseline at this timepoint. Plasma metabolites were glucuronidated and/or sulphated forms of phloretin. Intact phloridzin was not recovered. Phloretie acid was also detected in rat urine after phloretin gavage (Monge etal. 1984). 

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