From Big Medical Encyclopedia

POLYPHENOLS (synonym polyhydroxy phenols) — carbocyclic aromatic oxycompounds and their derivatives, regulate the enzymatic and non-enzymatic processes proceeding in a cell with education of free radicals; in medicine are used as pharmaceuticals (Benzonaphtholum, resorcin, etc.), and also for disinfection — cresols (see). Catecholamines (see) and the indolamines relating to P. are biologically active compounds. Items are molecular composition of alkaloids, steroids, flavonoids and other connections. Some P. are substances, irreplaceable in food, and their shortcoming leads to development of fragility of walls of capillaries. P.'s most exerts the expressed impact on cardiovascular system, reduces toxicity of a large number chemical and inf. agents. Items use as antioxidants (see. Antioxidants ) in the food industry, and also in production of food dyes. Items are a part of stabilizers of rubbers, motor fuel. Some P. are poisonous.

Most often P. are derivatives of two - and triatomic phenols (see): pyrocatechin, resorcin, hydrochinone (see), pyrogallol (see), floroglitsina. In a stand-at-ease of P. in the nature meet rather seldom, are more widely widespread their methyl - metoksi-and other derivatives. At plants there are fenoloksikislota — pyrocatechol, gallic, gentisinic, etc., acetophenones, phenyl acetic and hydroxy-cinnamic to - you. At enzymic oxidation of P. high-molecular polymers — lignins, tannins, melanina are formed.

The item — solid matters, well soluble in polar solvents (methanol, butanol) and in solutions of alkalis. All of them possess intensive absorption in the UF-spectral range. Items show properties to - t and with alkalis give phenolates, with ferric chloride form the complex salts having green, blue or brown coloring. This reaction is universal qualitative test on the Item. In the course of P.'s oxidation free radicals turn out (see. Radicals ), the combination to-rykh leads to polymerization (oxidizing condensation) therefore lignins and melanina are formed. Increase in a number of hydroxyl groups in a molecule P. increases P.'s ability to oxidation and to the reactions conducting to a rupture of benzene ring (see. Benzene ). Especially easily oxidation reactions are entered by P. having hydroxylic groups in o-and n-situation.

At an organism of animals there are fat-soluble antioxidants of the polyphenolic nature (phthiocol, vitamin E, ubikhinon) which prevent oxidation of fabric lipids and SH-group of proteins, stabilizing structure and functions of mitochondrial and cellular membranes and membranes of vessels and fabrics. The free radicals formed as a result of P.'s oxidation usually cause delay of both enzymatic, and non-enzymatic oxidation reactions.

P.'s metabolism in an animal organism is studied insufficiently, their such metabolites as methyl ethers and sulfoethers, and also glycosides glucuronic to - t which are removed with urine are known. P. in an organism of animals with participation of enzymes polifenoloksidaz are oxidized.

Qualitative and quantitative test of P. is carried out by spectrophotometric methods (see. Spektrofotometriya ), gas-liquid and liquid chromatography (see), and also their combination with mass spectrometry (see).

Bibliography: Baraby V. A. Biological effect of vegetable phenolic connections, Kiev, 1976; Biochemistry of phenolic connections, under the editorship of J. Har-born, the lane with English, M., 1968; 3 and p r about-metov M. N. Fundamentals of biochemistry of phenolic connections, M., 1974.

N. V. Prokazova.