Glycosides, also known asGlycoside，Glycosides, is made of sugar or sugar derivativesTerminal basecarbon atomCompounds formed by connecting with another class of non sugar substances (called aglycones, ligands or aglycones).Most glycosides are colorless, odorless and bitter.Minority glycosides such asXanthone glycoside, anthracene glycosideAnthocyaninEtc.A few have sweet taste, such asGlycyrrhizin。
3．Glycosidic bondPyrolysis of: Glycosides are easily exposed to dilute acid orEnzymatic hydrolysisProduce sugar and aglycone.However, there are several sugar molecules in the original glycosides in some plants, which are called primary glycosides. During hydrolysis, some sugar molecules can be removed first to generate secondary glycosides with fewer sugar molecules, and the secondary glycosides can be further hydrolyzed to obtain sugar and aglycones.After glycosides are hydrolyzed into glycosides, their solubility and efficacy in water are often greatly reduced. Therefore, during collection, processing, storage and manufacturingGlycosidesWhen the ingredients of Chinese herbal medicine are used, care must be taken to prevent hydrolysis.For example, try to reduce the breakage of plant body during collection, dry it as soon as possible after collection, keep it dry during storage, and do not place it in aqueous solution or acid solution for a long time during extraction.
4. Natural glycosides generally have certain optical activity, namelyoptical rotationMost of them are left-handed and not reducible.After hydrolysis, due to the formation ofreducing sugar, tends to become dextral andReducibility。This property can be used to identify glycosides in Chinese herbal medicine.The reducibility before and after hydrolysis is usually checked by Fehling test.
5．Identification: Some glycosides such assaponin、Xanthone glycosideEquivalencyLead acetateorBasic lead acetateThe reagent generates precipitation, which can be restored to the original glycosides after lead removal.This property can be used for the extraction of glycosides.
（3）Cyanoside(cyanogic glycosides): mainly refers to a class with α-HydroxynitrileGlycosides of.It is characterized by easy hydrolysis, especially with dilute acid andEnzyme catalysisWhen hydrolysis is faster, the generated aglycone α - hydroxynitrile is very unstable and can be immediately decomposed into aldehydes (or ketones) andHydrocyanic acid。Mainly distributed in RosaceaeRanunculaceae、Lonicera、leguminous、Lineaceae、EuphorbiaceaeandCrassulaceaeAnd other plants.for exampleRosaceaeMaturity of plantsfruitThe bitter almond。Small dosage has the effect of relieving cough and asthma, but large dosage will cause the danger of poisoning, so it should be used with caution.
（5）indoleIndox yl glycosides: are glycosides condensed from the hydroxyl group in aglycone indolyl alcohol and sugar.For example, indosine.
S-glucoside
Hydroxyl group of sugar terminal and aglyconeMercapto groupGlycosides condensed, mainly distributed inCruciferaeIn plants.for exampleTurnip glycoside, garlic, with special smell.(Specific to sulfhydryl compounds)
sugarTerminal baseCarbon is directly related toAglyconeuppercarbon atomConnected glycosides.The aglycones that make up the carbon glycosides areFlavonoids、anthraquinoneandgallic acidEtc.The formation of carbon glycosides is activated by the phenolic hydroxyl group of aglyconeAdjacencyOr the para hydrogen is dehydrated and condensed with the terminal hydroxyl group of the sugar.asVitexinandIsomangiferin。
