Hydroquinone glucoside

Clarys P, Barel A. Efficacy of topical treatment of pigmentation skin disorders with plant hydroquinone glucosides as assessed by quantitative color analysis. J Dermatol 1998 25(6) 412-14. 

UDP-glucose - - hydroquinone — UDP hydroquinone glucoside UDP-glucose - - phenol ct-glucoside — UDP + phenol -gentiobioside UDP-glucose -f- anthranilic acid — o-aminobenzoyl glucoside - - UDP... 

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... 

Bearberry Arctostaphylos uva-ursi (L.) Spreng is a small shrub, whose leaves contain arbutin, a hydroquinone heteroside, that yields hydroquinone after degradation by a j3-glucosidase enzyme. Hydroquinone acts by inhibiting the tyrosinase enzyme, which initiates the biochemical synthesis of melanin. At present, the use of this hydroquinone glucoside is becoming less and less frequent because of the restrictions on the use of synthetic hydroquinones for cosmetic applications and because of its well-known irritant effects on the skin (Maeda and Fukuda, 1991, 1996). 

Arbutin (= Hydroquinone-P-D-glucopyranoside) (phenol glucoside) Rhodiola sacra (Crassulaceae), Origanum majorana (Lamiaceae), Pyrus communis (Rosaceae) PEP (391 pM) [115]... 

Derivation A glucoside found in the leaves of the cranberry, blueberry, and manzanita shrubs, and in the roots, trunks, and leaves of most pear species. Pure arbutin can be prepared synthetically from ace-tobromoglucose and hydroquinone in the presence of alkali. 

Arbutin (Hydroquinone-B-D-glucoside) fits neither category. It is not widely distributed in plants, but is found in pears. 

Of the three isomers, catechol is the only member to occur naturally, namely in the leaves and branches of the oak and willow, in apples, onions, and crude sugar beet and in the tannin layer of mycorrhizas (ref.28). Its derivatives are widely distributed in higher plants. Hydroquinone occurs as the glucoside arbutin (4-hydroxyphenyl-D-glucopyranose) and resorcinol only in pyrolysis products in, for example, cigarette smoke. 

The formation of aryl D-glucosides is characteristic of insects as well as of plants. An enzyme has been prepared from the fat body of the locust which will catalyze the synthesis of arbutin from hydroquinone and uridine 5-(a-D-glucopyranosyl pyrophosphate),and homogenates of cockroach hepatic coecum have been shown to catalyze the formation of o-aminophenyl, S-D-glucopyranoside from the same glycosyl nucleotide and o-aminophenol. ... 

Quinol, hydroquinone, C6H4(OH)2(l, 4), may be obtained from arbutin, which is a glucoside of quinol, by hydrolysis with dilute acids, or by the action of emulsin. It is prepared by reducing quinone, C6H4O2 (677), by means of sulphur dioxide and water. 

Hydroquinone (39) and the glucoside arbutin (40) are derived variously from acetate-malonate, shikimic acid, or from tyrosine (Fig. 7.14). 

An effect of administration of the drug uva ursae is to cause darkening of the urine. Although leuco-anthocyanins are present in the plant, the effect is probably due to the glucoside of hydroquinone, arbutin, that the plant, in common with many Ericaceae, also contains. 

Simple phenols occur in higher plants much less frequently than was earlier supposed. The most important are hydroquinone and its glucoside arbutin (Fig. 104). Both also occur as their methyl ethers. They are known... 

Key abbreviation AA, ascorbic acid ADP, ascorbyl dipalmitate AG, ascorbyl glucoside AP, ascorbyl palmitate ARB, arbutin AZA, azelaic acid HQ, hydroquinone HQDM, hydroquinone dimethyl ether HQMB, hydroquinone monobenzyl ether HQME, hydroquinone monoethyl ether HQMM, hydroquinone monomethyl ether HQMP, hydroquinone monopropyl ether HQMPh, hydroquinone monophenyl ether KA, kojic acid MAP, magnesium ascorbyl phosphate. 

---