STEROLS (synonym sterola) — organic matters of group of steroids, alcohols of a tsiklopentanpergidro-phenanthrene row; in a human body and animals are important participants of a lipometabolism, the content of nek-ry sterols serves as additional diagnostic test at the diseases which are followed by disturbances in blood serum and urine lipometabolism (see), frustration of endocrine system, etc. Free S. and S. in the form of ethers with fatty acids (see) are a part of cellular membranes (see Membranes biological). Some sterols use as pharmaceuticals.
Pages are formed in all animals and vegetable organisms. In scientific literature they are divided into S. of animals (zoosterins), by S. of plants (phytosterols) and S. of mitselial-ny fungi and yeast (mycosterols). Are not synthesized by S.'s bacteria. More than 100 individual Pages are allocated.
The major zoosterin is cholesterol (see). Contains in a human body on average apprx. 140 g (0,2% of body weight) of cholesterol, and the amount of free cholesterol prevails over amount of its ethers. Much less in a human body contains other S. — products of biosynthesis and a catabolism of cholesterol — a holestanol, a 7-degidrokholestanol, a desmosterin, a 7-degidrokholesterin, coprosterol (a product of microbic recovery of cholesterol in a large intestine). The most important phytosterols are the stigmasterol making 12 — 25% of not saponifiable fraction of soybean oil and being (along with beta sitosterol) the most available material for synthesis steroid hormones (see), and the beta sitosterol which found application as the hypolipidemic medicine interfering absorption of cholesterol in intestines. Widespread mycosterol is the ergosterol used along with other connections for synthesis of vitamin D (see. Calciferols ).
Pages represent colourless crystal substances, water-insoluble and soluble in organic solvents. S.'s allocation from natural sources is carried out by extraction with the subsequent hromatografichesky division and crystallization. S.'s analysis is based on S.'s ability like cholesterol to give Libermann's reaction — Burkharda with acetic anhydride and a chamois to - that, Chugayev's reaction at effect of mix of chloride acetyl and zinc chloride, etc. consists in determination of optical density of the formed painted product (see. Colorimetry ). Pages form slightly soluble complexes with saponins (see). Sludge formation with one of them — digitonin — is used for the separate analysis of free S. and their ethers in mix. The most modern method of the analysis of S. is thin layer and gas-liquid chromatography (see).
Initial products of biosynthesis of S. are acetic and low-new to - you in shape atsetil-KOA and malonil-KOA, and the first specific intermediate compound — mevalonovy to - that. At animals and the person a mode of formation mevalonovy to - you limit synthesis of cholesterol. Get to an animal organism of S. also with food: cholesterol — with animal products, phytosterols — with vegetable products.
See also Steroids .
Bibliography: Akhrem A. A. and Titov Yu. A. Full synthesis of steroids, M., 1967; F and z e r L. and F and z e p M. Steroids, the lane with English, M., 1964; Briggs M. H. a. Brotherton J. Steroid biochemistry and pharmacology, L. — N. Y., 1970; Nes W. R. The biochemistry of plant sterols, Advanc. Lipid Res., v. 15, p. 233, 1977.
A. H. Klimov, D. V. Ioffe.