Hazard
Questionable carcinogen.
Chemical Properties
Cholesterol occurs as white or faintly yellow, almost odorless,
pearly leaflets, needles, powder, or granules. On prolonged
exposure to light and air, cholesterol acquires a yellow to tan color.
Chemical Properties
White to faintly yellow cryst. powder
History
Cholesterol was discovered in 1769 by Poulletier dela Salle (1719–1787), who isolated
the compound from bile and gallstones. It was rediscovered by Michel Eugène Chevreul
(1786–1889) in 1815 and named cholesterine. The name comes from the Greek words khole
meaning bile and steros meaning solid or stiff . The “ine” ending was later changed to “ol” to
designate it as an alcohol.
Definition
ChEBI: A cholestanoid consisting of cholestane having a double bond at the 5,6-position as well as a 3beta-hydroxy group.
Definition
cholesterol: A sterol occurringwidely in animal tissues and also insome higher plants and algae. It canexist as a free sterol or esterified witha long-chain fatty acid. Cholesterol isabsorbed through the intestine ormanufactured in the liver. It servesprincipally as a constituent of bloodplasma lipoproteins and of thelipid–protein complexes that formcell membranes. It is also importantas a precursor of various steroids, especiallythe bile acids, sex hormones,and adrenocorticoid hormones. Thederivative 7-dehydrocholesterol isconverted to vitamin D3 by the actionof sunlight on skin. Increased levelsof dietary and blood cholesterol havebeen associated with atherosclerosis,a condition in which lipids accumulateon the inner walls of arteries andeventually obstruct blood flow.
General Description
Cholesterol is a minor sterol present in plants. It is majorly associated with the plant membranes and is a constituent of leaf surface lipids.
Pharmaceutical Applications
Cholesterol is used in cosmetics and topical pharmaceutical
formulations at concentrations of 0.3–5.0% w/w as an emulsifying
agent. It imparts water-absorbing power to an ointment and has
emollient activity.
Cholesterol also has a physiological role. It is the major sterol of
the higher animals, and it is found in all body tissues, especially in
the brain and spinal cord. It is also the main constituent of
gallstones.
Biochem/physiol Actions
Cholesterol is a lipid that makes up about 20-25% of the structural components of the cell membranes. It determines the fluidity and permeability of the membrane, making it permeable to water but not to ions and protons. Cholesterol also regulates the functions of the transporters and signaling proteins present on the plasma membrane. The major sites of cholesterol synthesis are small intestine and liver.
Safety
Cholesterol is generally regarded as an essentially nontoxic and
nonirritant material at the levels employed as an excipient. It has,
however, exhibited experimental teratogenic and reproductive
effects, and mutation data have been reported.
Cholesterol is often derived from animal sources and this must
be done in accordance with the regulations for human consumption.
The risk of bovine spongiform encephalopathy (BSE)
contamination has caused some concern over the use of animalderived
cholesterol in pharmaceutical products. However, synthetic
methods of cholesterol manufacture have been developed.
storage
Cholesterol is stable and should be stored in a well-closed container,
protected from light.
Purification Methods
Crystallise cholesterol from ethyl acetate, EtOH or isopropyl ether/MeOH. [Hiromitsu & Kevan J Am Chem Soc 109 4501 1987.] For extensive details of purification through the dibromide, see Fieser [J Am Chem Soc 75 5421 1953] and Schwenk and Werthessen [Arch Biochem Biophys 40 334 1952], and by repeated crystallisation from acetic acid; see Fieser [J Am Chem Soc 75 4395 1953]. Like many sterols, cholesterol gives colour reactions with conc H2SO4: When cholesterol is dissolved in a small volume of CHCl3 and mixed with conc H2SO4, the colour of the organic layer becomes crimson, then changes to purple and on further standing in air it turns to blue, then green and finally yellow. The H2SO4 layer develops a green fluorescence. [Beilstein 6 III 2607, 6 IV 4000.]
Incompatibilities
Cholesterol is precipitated by digitonin.
Regulatory Status
Included in the FDA Inactive Ingredients Database (injections;
ophthalmic, topical, and vaginal preparations).
Included in nonparenteral medicines licensed in the UK. Included
in the Canadian List of Acceptable Non-medicinal Ingredients.
