Flavonol sulfates

Ogundipe, 0.0., Moody, J.O., and Houghton, P.J., Occurrence of flavonol sulfates in Alchornea laxiflora, Pharm. Biol (Lisse, Netherlands), 39, 421, 2001. 

The preferred solvent system used for the separation of flavonoids on reversed-phase stationary phases is methanol-water, followed closely by acetonitrile-water. Usually, acetic or formic acid is added (sometimes phosphoric acid, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and perchloric acid), which enables improved separation and prevention of peak tailing with respect to the phenolic character of the flavonoids. Ion pairing has also been used for improving the separation of neutral glycosides from flavonol sulfates. 

Glycosides of flavonoid sulfates occur in a number of plants (Fig. 11.12) (Harbome, 1991). More than 100 flavone and flavonol sulfates from more than 250 species and 30 families have been characterized compounds of this type may be recognized by examination of their UV spectra before and after addition of HCl and aryl-sulfatase (Barron and Ibrahim, 1988 Harbome, 1991 Varin, 1992). 

Grandmaison, J. Ibrahim, R.K. (1996). Evidence for nuclear protein binding of flavonol sulfate esters in Flaveria chloraefolia. Journal of Plant Physiology, 147, 653-660. 

Three distinct chemotypes were observed. Taxa from each of the three areas noted above exhibited unique combinations of the compounds and compound types, although there was a degree of variation within most groups, as one might expect. The North American chemotype was characterized by very high frequency of the sulfated cinnamic-acid derivatives, a frequency of flavonol derivatives of... 

N.A. Malva mtundifolia L. M. sylvestris L. Flavonol glycosides, gossypin-3-sulfate, mucilage, tannins, anthocyanin, malvin." A demulcent, a poultice to reduce swelling and draw out toxins. Internally to reduce gut irritation, laxative effect. 

The sulfate group can be transferred to other nucleophilic atoms, such as nitrogen or sulfur, resulting in the formation of sulfamates (RR — N — SO3) and thiosulfates (R — S — SO3), respectively, rather than sulfates. The sulfotrans-ferases (STs) that catalyse the sulfonation of drugs, hormones and neurotransmitters in animals, like those in plants that catalyse similar reactions with flavonols as... 

STs are simple phenols such as 4-nitrophenol, phenolic catecholamine neurotransmitters such as dopamine, phenolic steroids such as the estrogens, non-phenolic hydroxy-steroids such as dehydroepiandrosterone (DHEA) and in plants, flavonols such as quercetin. Cytosolic STs are also actively involved in the Al-sulfation of alkyl- and aryl-amines, as well as alkyl- and arylamides leading in some cases to the formation of unstable metabolites. 

A particularly interesting feature is represented by 5-OH substituted flavonols such as quercetin (1) and morin (6, Fig. 5a). In these molecules, the 5-OH group is able to hamper ESIPT from the 3-OH to the carbonyl oxygen favouring internal conversion." These flavonols establish specific interactions with their microenvironment, e.g. upon binding to biomolecu-les"" " or when placed in specific microenvironments such as Sodium Dodecyl Sulfate (SDS) micelles" and in lipid nanocapsules. 

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