Glycosides solubility

Vitamin rarely occurs in plants. However, Solanumglaucophjllum Solanum malacoyyhn Cestrum diumum and TrinetumJlavescens have been shown to contain water-soluble glycosides of vitamin D analogues with 1 a,25-dihydroxy-vitarnin D activity (16—22). The vitamin D content in various plant and animal materials is shown in Table 3. Vitamin D occurs naturally in all animals (24). 

Crocin is a yellow-orange glycoside that is freely soluble in hot water, slightly soluble in absolute alcohol, glycerol, and propylene glycol, and insoluble in vegetable oils. Crocin melts with decomposition at about 186°C and has absorption maxima in methanol at about 464 nm and 434 nm. 

Benzaldehyde Cyanohydrin. This cyanohydrin, also known as mandelonitrile [532-28-5] is a yellow, oily Hquid, insoluble in water, but soluble in alcohol and diethyl ether. Mandelonitrile is a component of the glycoside amygdalin [29883-15-6] a precursor of laetdle [1332-94-7] found in the leaves and seeds on most Prunus species (plum, peach, apricot, etc). In 1832, mandelonitrile was the first cyanohydrin to be synthesized. 

Nucleosides are much more water-soluble than the free bases because of the hydrophilicity of the sugar moiety. Like glycosides (see Chapter 7), nucleosides are relatively stable in alkali. Pyrimidine nucleosides are also resistant to acid hydrolysis, but purine nucleosides are easily hydrolyzed in acid to yield the free base and pentose. 

Under aqueous conditions, flavonoids and their glycosides will also reduce oxidants other than peroxyl radicals and may have a role in protecting membranal systems against pro-oxidants such as metal ions and activated oxygen species in the aqueous phase. Rate constants for reduction of superoxide anion show flavonoids to be more efficient than the water-soluble vitamin E analogue trolox (Jovanovic et al, 1994), see Table 16.1. 

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. 

The solubility of iridoids depends on their state (free, glycosylated, acetylated), but usually they are extracted with polar solvents methanol, ethanol, aqueous alcohols, and rarely acetone. Iridoid glycosides are more or less stable some of them are very sensitive to acids and alkalis. Some iridoid glycosides such as aucubin suffer color modification after chemical or enzymatic hydrolysis they give first a blue to green... 

Many solvents such as methanol, acetone, ethanol, and water are used for anthocyanin extraction due to their polar character since most anthocyanins occur naturally as glycosides. Anthocyanin glycosides have higher solubility in water than the corresponding aglycons. In addition, in most fruits and vegetables, anthocyanin pigments are located in cells near the surface. " ... 

A traditional system for the preparation of table olives, involves a treatment of the fresh fruit with a solution of NaOH to hydrolised the bitter glycoside oleuropein, followed by a lactic fermentation in brine. The modifications that take place on pectic polysaccharides of olives (Manzanilla variety) during this process was smdied. Processing induced a net loss of polysaccharides soluble in sodium carbonate and a paralel accumulation of water and Imidazole/HCl soluble polysaccharides. A general decrease of the apparent molecular weight of water and carbonate soluble polysaccharides was also detected. 

Polychaete worms belonging to the genera Nereis and Scolecolepides have extensive metabolic potential. Nereis virens is able to metabolize PCBs (McElroy and Means 1988) and a nnmber of PAHs (McElroy 1990), while N. diversicolor and Scolecolepides viridis are able to metabolize benzo[a]pyrene (Driscoll and McElroy 1996). It is worth noting that apart from excretion of the toxicant, polar, and mnch more water-soluble metabolites such as the glycosides formed from pyrene by Porcellio sp. (Larsen et al. 1998) may be mobile in the interstitial water of the sediment phase. 

With the death of the bean, cellular structure is lost, allowing the mixing of water-soluble components that normally would not come into contact with each other. The complex chemistry that occurs during fermentation is not fully understood, but certain cocoa enzymes such as glycosidase, protease, and polyphenol oxidase are active. In general, proteins are hydrolyzed to smaller proteins and amino acids, complex glycosides are split, polyphenols are partially transformed, sugars are hydrolyzed, volatile acids are formed, and purine alkaloids diffuse into the bean shell. The chemical composition of both unfermented and fermented cocoa beans is compared in Table 1. 

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