Phenols, acid sulfates glycosides

The glycosidic linkage of III bears a physiological resemblance to that of another conjugation product found in urine, the phenolic acid (or ethereal ) sulfate (V). Many phenols can be conjugated with either D-glucuronic acid or sulfuric acid ... 

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. 

Thin-layer analysis of the hydrolysates requires removal of the mineral acid used for hydrolysis. Ion exchange resins are widely used, but some classical procedures are also very useful. After hydrolysis with 1 M sulfuric acid, the acid may be removed as barium sulfate by adding barium carbonate solution. Small amounts of 1 M hydrochloric acid can be removed in vacuo, and larger amounts of this acid can be conveniently removed from an aqueous hydrolysate by repeated washing with a 10% solution of di-n-octylmethylamine in chloroform etc. The hydrolysates plant of plant glycosides usually contain interfering compounds such as phenolics. These can be removed by extracting the hydrolysates with diethyl ether or ethyl acetate (26). 

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