Cholesterol glycoside

Neutral alumina is generally recommended for separation of alkaloids, polyaromatic hydrocarbons, cholesterol, glycosides, vitamins and various pharmaceuticals. Acidic alumina yields a good separation of fats and waxes, fatty acids, morphine derivatives, and food dyestuffs, while basic alumina plays an essential role in the separation of alkaloids, biogenic amines, phenothiazines, hydrocarbons, insecticides, and some synthetic bases. 

CD spectra of tautomeric and protonated cyclic adenosine derivatives e.g. 73 have been described. A review of the chiroptical properties of cholesterol glycosides and chirality distinction has appeared (e.g. D-glucose and L-glucose lead to red and blue shifts respectively). CD has been used for chirality determination of dideoxy-g/yccro-mannonopyranose-derived 74. The C2 chir-... 

Cholesterol is probably the best known steroid because of its association with atherosclerosis. However, biochemically it is also of significance because it is the precursor of a large number of equally important steroids that include the bile acids, adrenocortical hormones, sex hormones, D vitamins, cardiac glycosides, sitosterols of the plant kingdom, and some alkaloids. 

There has been considerable discussion regarding the mode of action of the sea cucumber and starfish saponins. Both the triterpene and steroidal glycosides inhibit both Na/K ATPase and Ca/Mg ATPase 06) possibly as a result of their aglycone structures. However, their detergent properties cause membrane disruption which will influence the activity of membrane-bound enzymes such as the ATPases. In investigating the actions of saponins on multilamellar liposomes, it was found that cholesterol serves as the binding site for such saponins and that cholesterol-free lip-somes are not lysed by saponins 107). 

Steroids, compounds with a cyclopenta[a]phenanthrene skeleton (15), include a wide range of natural products such as sterols (e.g., cholesterol), sex hormones, adrenocorticoid hormones, cardiac glycosides and vitamin D [31]. Sterols are steroids having a hydroxyl group at position 3 of the basic skeleton. Steroids can be found both in plants and in animals. 

The polyene antibiotic nystatin (5 25pg/mL, 10 minutes) and the cardiac glycoside digitoxin (5 pg/mL, 10 minutes) bind cholesterol and can remove it from cell membranes, which leads to inhibition of caveolae uptake (60). Regarding its effect on clathrin uptake, no comment can be given at this time. 

Sterols are widely distributed in both plants and animals. Many are of vital importance to animal physiology, such as cholesterol, the bile acids, vitamin D, sex hormones, and corticoid hormones. Many have value as medic-inals, such as the cardiac glycosides, hormones, and steroidal antibiotics. The occurrence and physiological properties of representative steroids are included in Table 30-2. 

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