Glycoside acylation

Acyclic diterpene glycosides Acyl flavonol di-gycoside Adenine... 

Flavone glycosides often occur as acylated derivatives either with aliphatic or aromatic acids. Hydroxy-cinnamic acid derivatives are the most frequent in nature and MS fragmentations of these types of compounds show ions produced by the loss of 146,162,176, or 206 m.u., corresponding to the losses of the acyl residues />-coumaroyl, caffeoyl, femloyl, or sinapoyl, respectively. Brassicaceae species are rich in flavonoid glycosides acylated with hydroxyl-cinnamic derivatives, and most of them... 

Keywords Plant sterol phytosterol sterol conjugate steryl ferulate gamma-oryzanol steryl glycoside acylated steryl glycoside steryl ester free sterol. 

Purification of anthocyanins extracted fi om berries is not deemed necessary if measurement of UV/VlS-absorption (>500 nm) for quantification is used. Except in cases of adulteration with red or blue food colorants the measurement wave lengths are selective enough to quantify anthocyanins in crude extracts. If berry anthocyanins are extracted from complex matrices (dietary supplements or food products) removal of other ingredients extracted is advantageous [125, 126]. For structural elucidation, for the analysis of the specific glycosidation/acylation pattern or the requirement to enrich anthocyanins from low content sources, crude extracts need to be purified and eventually fractionated [63, 67, 114, 118, 127-131]. 

The type of solvent to be used for the extraction of flavonoids from solid foods depends mainly on the type of compounds to be extracted, that is whether they are aglycones, glycosides, acylated or methoxylated flavonoids, etc., which might affect their polarity and thus their solubility on the selected solvent. Also, the degree of polymerization of proanthocyanidins or the cationic nature of anthocyanidins should be taken into account when selecting the extraction solvents. 

Mannosides are difficult to obtain since here a 2-O-acyl group blocks the -position. 2-O-Benzyl-a-mannosyl bromides give, however, high yields of pure -glycosides with a heterogeneous silver silicate catalyst preventing anomerization and SnI reaction of the bromide H. Paulsen, 1981 B, Q. 

Derivatives. Many derivatives of acylated phlorogluciaols that bear a benzene ring substituent or an ether or glycoside linkage occur ia aature. Examples are cotoia [479-21-0] (52) ia coto bark and conglomerone [480-25-1] (53) ia Eucalyptus conglomerata. 

Pyridazine-3(2H)-thione, 4,5,6-triphenyl-ring contraction, 3, 29 Pyridazineth lones acylation, 3, 37 glycosides... 

Note. Acyl substituents on anomeric OH are designated (as above) by 0-acyl prefixes. However, anomeric 0-alkyl derivatives are named as glycosides (see 2-Carb-33). 

Anthocyanins are water-soluble pigments, as acylation of the carbon skeleton by glycosides increases the polarity of these molecules. Furthermore, according to the pH conditions, the heterocyclic oxygen atom may be found in cation form, further increasing the molecule s polarity. 

Six anthocyanidins are commonly found in plants and plant-derived foods and beverages pelargonidin, cyanidin, delphinidin, peonidin, petunidin, and malvidin. Their structures differ in the number and position of hydroxyl and methoxyl groups on the flavan nucleus. The most commonly occurring anthocyanidin is cyanidin, and all these anthocyanidins are found in plants as glycosides with or without acylation, leading to around 400 different stractures. 

Naito, K. et al., Acylated pelargonidin glycosides from a red potato. Phytochemistry, Al, 109, 1998. 

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