Cerebrosides

CEREBROSIDES (galactolipins), substances from the group of lipoids, first described by Müller in 1858; obtained by the splitting of protagon by alkalis. C. apparently enter into the composition of all tissues of the organism, but in the greatest quantity they are found in brain tissue (up to 7.3% according to some data and from 2% to 9% according to others, calculated by weight of the dry organ). The amount of C. in different parts of the brain is not the same: in gray matter there is less of them than in white matter, in which they make up 2.9% of the weight of fresh brain and 13% of dry matter. Gray matter of the subcortical ganglia of the brain is richer in C. than the gray matter of the cortex. Differ from each other in the quantitative content of C. and such parts of the brain as the cerebral hemispheres, the pons Varolii, the medulla oblongata, the spinal cord, and the cerebellum. The content of C. is also not the same in functionally different areas of the human cerebral cortex. Studies by Linnert speak of rather significant differences in the content of C. in the brains of different species of animals. The highest content of C. is in the brain of the horse, then the pig, ox, rabbit, cat, monkey and finally the dog. C. were not found in the brain of fish. In the process of embryonic development of the brain, along with changes in its chemical composition, there is also a change in the content of C. in it; in the brain of the embryo they are also absent and appear in the first weeks after birth, and with age their quantity increases. Upon hydrolysis, sphingosine, galactose, and a higher fatty acid are formed. The structure of C. can be represented by the following formula: Individual C. differ from each other in the nature of the fatty acid residue included in their composition. Thus, kerazin contains the residue of lignoceric acid CH₃.(CH₂)₇.CH₂.CH₂(CH₂)₁₂. .CH₂.COOH, cerebron - the residue of α-hydroxy-lignoceric acid CH₃.(CH₂)₇.CH₂.CH_£. .(CH₂)₁₂.CHOH.COOH, nervon - the residue of α-unsaturated nervonic acid CH₃.(CH₂)₇.CH:CH. .(CH₂)₁₂.CH₂.COOH, hydroxynervon - the residue of α-hydroxynervonic acid CH₃.(CH₂)₇. .CH:CH.(CH₂)₁₂.CHOH.COOH. Apparently there exist C. containing other acid radicals as well. By chemical properties, C. are very close to each other. The C. described in the literature under various names are often identical, often represent not chemical individuals, but a mixture of substances. The most studied are cerebron, kerazin, and nervon. Cerebron [phrenosine Thudicum], pseudocerebrin Gamgee, C₄₈H₉₃NO₉, can be obtained directly from the brain by extraction with a mixture of alcohol and chloroform or alcohol and benzene at t° 50°. Cerebron is insoluble in ether, in alcohol, acetone, benzene it dissolves only when heated. Cerebron fuses at about 130°, releasing drops of liquid (liquid crystals?); at 212° it completely turns into a liquid. Cerebron rotates to the right. For 5% solutions in 75% methyl alcohol containing chloroform, [α]D = +7.6°. A 10% solution in pyridine at 20° gives [α]D = +3.74°. Reactions for cerebron can be: 1) yellow, turning into red-purple coloring upon the action of concentrated H₂SO₄; 2) when heating traces of cerebron with 0.5 cm³ of water and after cooling adding 2 drops of 2% alcoholic solution of α-naphthol and 1 cm³ of pure concentrated H₂SO₄, so that the liquids do not mix, a violet stripe is formed at the place of contact; 3) when boiling cerebron with orcin and concentrated, iron-containing HCl, green and blue coloring occurs. The purity of cerebron preparations is tested by the following reactions: 1) completely pure cerebron even in large amounts after ashing with soda and nitric acid does not give reactions for phosphoric acid; 2) crystallization test; completely pure cerebron when boiled with a small amount of methyl alcohol or with methyl alcohol containing 10% chloroform, after some time turns into crystals resembling cholesterol; 3) examination in a polarizing microscope with a gypsum plate allows to detect kerazin in the presence of cerebron and cerebron in the presence of kerazin. Kerazin (homocerebrin) discovered by Thudicum, very close in chemical properties to cerebron, differs by greater solubility in hot alcohol, which is used for its separation from cerebron. Kerazin can also be separated from cerebron in the form of a benzoylated derivative. Kerazin is precipitated from solutions upon cooling in the form of a jelly-like mass, which after drying in vacuum turns into a powder, when dried in the air - into a transparent waxy mass. Like cerebron, when heated at t° 100-180° kerazin passes into a liquid state. Rotates to the left: a 10% solution in pyridine at 18° has [α]D = -2.5°. Kerazin gives the same reactions as cerebron; to distinguish them, the test with a gypsum plate in a polarizing microscope can be used. Nervon was isolated by Frankel and Kafka from a brain extract with petroleum ether after the removal of cholesterol by adding a weakly alkaline solution of lead sugar. [α]D = -4.33° for a 9.45% solution of not quite pure preparation. Nothing is known regarding the physiological significance and changes of C. in the organism. There are observations that in the disease of Gaucher in the liver and spleen the amount of C. increases. When C. are introduced into the organism of a dog, the excretion of sphingosine with urine was observed. Under the action of pancreatic lipase and emulsin, C. are not split. In the brain, the enzyme cerebrosidase was found, capable of hydrolyzing C. C. apparently take an active part in the life process of the brain. States of rest, excitation and irritation of the central nervous system are characterized by different content of C. in it. In some mental diseases, for example, in progressive paralysis, their amount in the brain significantly decreases. Under the influence of a number of narcotic and hypnotic substances, such as urethane, scopolamine, chloral hydrate, etc., the breakdown of C. in the isolated frog brain decreases. The basis of the methods for quantitative determination of C. is the determination of the reducing ability of the alcoholic extract before hydrolysis and after it by the Hagedorn-Jensen method or Bertrand method; from the obtained difference, the amount of galactose is calculated and converted to cerebrosides.

M. Karyagina.