Glycosides arbutin

The plants of the family Ericaceae are used therapeutically. The active principle is hydroquinone, which is the hydrolytic product in alkaline urine of the glycosides arbutin and methylarbutin (both inactive), which occur in the two Ericaceae drugs ... 

The three isomeric dihydroxybenzenes, C6H4(OH)2, are catechol (pyro-catechin) discovered by H. Reinsch resorcinol by Hlasiwetz and Barth by fusing guaiacum, galbanum, or ammoniacum resins with caustic potash and quinol (hydroquinone) by Pelletier and Caventou (1820) and Wohler (1844 see p. 326). Hydroquinone had been obtained by A. Kawalier, who called it arctuvin , by hydrolysis of the glycoside arbutin (Ci2Hie07) which he discovered in the leaves of the bear-berry. The orientations of the three di-hydroxybenzenes were established by Th. Petersen. Resorcinol was synthesised from benzene by Korner. ... 

N.A. Flavonoid glycosides, chimpahilin, sesquiterpenes, arbutin, ursolic acid.186 Anti-inflammatory, relieve pain, improve myocardial circulation. 

Two catechins, ( + )catechin and ( — )epicatechin, and two leucoanthocyanins were isolated from Bartlett pears by Nortje (165).. Durkee et al. (166) identified arbutin (p-hydroxphenyl-/ -D-glucoside) in mature and immature pears. Several flavanol glycosides such as quercetin 3-glucoside, isorhamnetin-3-glucoside, isorhamnetin-3-rutinoside, isorham-netin-3-galactoside, and quercetin-7-xyloside were identified by Duggan (167). 

For phenolics in fruit purees and jams (54), an HPLC condition similar to that used for apple juice, but with acidified water (5% formic acid) and methanol, was utilized as a solvent system. In most cases, detection was achieved with diode array detection, at UV 280 nm and 320 nm. The different phenolic compounds were identified by their UV spectra and by chromatographic comparisons with authentic standards. Several classes of phenolic compounds (cinnamic acids, catechins, dihydrochalcones, and flavonol glycosides) could be detected along with arbutin in... 

Chlorogenic acid (43-108 mg/kg fw. as caffeic acid) [19] and arbutin (1-gucosyl-1,4-dihydroxy-benzene) are the main non-flavonoid phenolics. Catechin and, especially, epicatechin (7-12 mg/kg) have also been found in pears [19]. In the peels, a complex flavonoid pattern of quercetin and isorhamnetin 3-glycosides has been detected. The occurrence of characteristic flavonols acylated with dicarboxylic acids in pears has recently been reported [28]. 

The simple phenol hydroquinone (see above) is derived from hydroxybenzoic acid. Upon glucosylation, arbutin, a simple phenol glycoside, is formed. 

Pears (Pyrus communis) were cultivated by the Phoenicians and later by the Romans. There are now in excess of 500 named varieties worldwide. The total phenolic content of some cultivars of pears has been shown to be between 1235 and 2500 mg/kg in the peel and 28-81 mg/kg in the flesh (Galvis-Sdnchez etal. 2003). The phenolic composition of pears is very similar to that of apples containing 5-0-caffeoylquinic acid, 4-O-p-coumaroylquinic acid, procyanidins and quercetin glycosides. The main difference in the phenolic content of apples and pears is the presence of hydroquinone glucoside (arbutin) (Figure 7.24) in pears and the hydroxychalcones in apples (Spanos and Wrolstad 1992). The average... 

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