Tangeretin

Figure 5.7 Separation of tangeretin and heptamethoxyflavon by recycle HPLC R, recycle C, collected 1, tangeretin 2, heptamethoxyflavon. Reprinted from Essenze Derivati Agrumari, 63, L. Mondello et al., Tsolamento di polimetossiflavoni dagli olii essenziali di arancia dolce e di mandarine mediante cromatografia su colonna e HPLC semipreparativa con riciclo , pp. 395-406, 1993, with permission from Essenze Derivati Agmmari.

Flavonoids in the diet have been widely promoted as important antioxidant contributors. Their neuroprotective properties, because of this effect, have been demonstrated by several workers. However, they have also been demonstrated to have MAOI activity and this has been proposed as part of the explanation of the use of the common herb, St Johns Wort, Hypericum perforatum L., as an antidepressant. This dual role has now been proposed for a variety of flavonoids, such as kaempferol (22) from the leaves of Ginkgo biloba L., a widely used herbal product which has been suggested as a preventative agent against neurodegeneration. Quercetin (23), similarly, has also shown to inhibit MAO-B " and reverse the effects of induced catalepsy, which mimics the bradykinesia associated with PD. Tangeretin (24) also inhibits MAO-B and crosses the blood brain barrier in a rat model. 

Different extracts of Citrus were subjected to SPE on Cig cartridges to remove polar components. The retained flavonoids (mainly flavanones) were eluted with methanol-dimethyl sulfoxide, which enhanced solubility of hesperidin, diosmin, and diosmetin. Recoveries of eriocitrin, naringin, hesperidin, and tangeretin from spiked samples of mesocarp tissue exceeded 96%. Flavones were relatively abundant in the leaves. ... 

Tangeretin C. Clementina, C. tangerine, C. limon Citrus sinensis. Citrus aurantium. vt (23,46)... 

Figure 1 Chemical structure of polyphenolics in citrus. (A) Bergamottin, (B) 6 7 dihydroxybergamottin, (C) Naringenin, (D) Naringin, (E) Rutin, (F) Tangeretin, and (G) Nobiletin.

Quercetin has been found to inhibit P-gp-mediated efflux of ritonavir in Caco-2 cells (47), to reduce the oxidation of acetaminophen in rat liver microsomes and HepG2 cells (48), and to inhibit the metabolism of midazolam and quinidine in human liver microsomes (49). It did not have an effect on CYP3A4-mediated metabolism and P-gp-mediated transport of saquinavir (41). Rutin was demonstrated to moderately increase the uptake of idar-ubicin in an isolated perfused rat lung model, and also the outflow recovery of the major metabolite idarubicinol, possibly by affecting P-gp (45). Nobe-litin and tangeretin were shown to inhibit OATP-B-mediated uptake of estrone-3-sulfate into human embryonic kidney cells (23). 

Flavones contribute to plant tissue color provided that they occur in high concentrations or are complexed with metal ions. Some flavones participate in taste for example, the highly methoxylated aglycones nobiletin, sinensetin and tangeretin are responsible for the bitter taste of citrus peel. On the other hand, some glycosylated flavones (for instance neodiosmin and rhoifolin) reduce the bitterness of some substances (limonin, naringin, caffeine, quinine) [2]. 

Flavones (Figure II. 3.7) are less commonly found in plants, but often occur in citrus. Poly-methoxylated flavones, which include no-biletin, sinensetin, and tangeretin, are the characteristic features in citrus plants. Flavones are generally detected at 360 or 370 nm. The elution order, when analyzed as described in the Basic Protocol, is rhoifolin, luteolin, and apigenin (Table 11.3.1). 

Substantial quantities of luteolin-7-O-glucuronide, luteolin-7-O-glucoside, and luteolin-7-O-rutinoside occur in Red Oak Leaf and Lollo Rosso, two red-leaved varieties of lettuce (Lactuca sativa) [Llorach et al., 2008], Polymethoxylated flavones such as nobiletin, scutellarein, sinensetin, and tangeretin (Fig. 1.8) are found exclusively in citrus species [Crozier et al., 2006c], while diosmetin-7-O-glucuronide has been isolated from the fruits of a Chinese herb, Luffa cylindrical. 

Shikonin (= 1 7 -isomer of Alkannin) (naphthoquinone) Tangeretin (= 5,6,7,8,4 -Pentamethoxyflavone) (flavone)... 

Pericarpium citri reticulatae virde, Pericarpium citri reticulatae, Fructus aurantii, Fructus, aurantii, immaturus Naringin, naringenin, hesperidin, neohesperidin, tangeretin, synephrine ESI-MS, positive ion mode Ding et al., 2007... 

Chemical structures of flavonoids. These flavonoids consisted of three groups flavone (apigenin and lutolin), flavonols (flavonol, kaempferol, quercetin, myricetin, tangeretin, and nobiletin) and isoflavones (daizein, genistein, biochanin A, and equol). 

Most flavonoids are diphenylpropanoids that occur ubiquitously in plant foods that are important constitnents of human diet. The major flavonoids are apigenin, quercetin, tangeretin, nobiletin, kaempferol, myricetin, genistein, daidzein, and luteolin (Fignre 6.2). Althongh flavonoids are generally considered to be nonnutritive agents, interest in flavonoids has arisen because of their potential role in the prevention of human cancer." ... 

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