Ester, estrogen fatty acid

In the case of androgens as with estrogens there is occasionally need for treatment of patients with chronic sustained doses of these drugs. Resort is made to esters of the androgen with long-chain fatty acids in order to provide oil-soluble agents ... 

Sterols are a class of lipids that consist of a steroid and an alcohol. The most physiologically abundant sterol in humans is cholesterol, which is an integral part of the plasma membranes, confaring the fluidity of the lipid bilayer. Due to its amphipathic nature, cholesterol is an important structural component of cell membranes and the outer layer of plasma lipoproteins. Cholesterol plays an essential role both in the structure of cells and as a precursor to corticosteroids, mineral corticoids, bUe acids, vitamin D, and sex hormones such as testosterone, estrogen, and progesterone. As excess free cholesterol has cytotoxicity in cells, it is estrailied to a fatty acid to become a cholesteryl ester, a neutral form of cholesterol. Cholesteryl esters can be stored in the hpid droplets of cells without cytotoxicity, and therefore cholesterol esterification is increased whrai free cholesterol content in cells becomes excessive. 

Figure 1.4 The core structure and representatives of sterol lipids, (a) The core structure of the majority of the sterol species or from which the sterol species are resulted, (b) The representative structures of cholesterol (R = H) and cholesteryl esters (R = a fatty acyl), (c) A representative structure of the steroid subgroup species (i.e., estrogen), (d) A representative structure of the secosteroid subgroup (i.e., vitamin Dj). (e) A representative structure of the species among the bile acid subgroup of sterol (i.e., cholic acid).

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