Inosit

Inosit, C₆H₁₂O₆+H₂O, formerly called muscle sugar due to its sweet taste and identical elementary composition with hexoses (C₆H₁₂O₆), is in fact not a carbohydrate but belongs to hydroaromatic compounds and represents hexahydro-hexaoxy-benzol. It was discovered by Scherer; synthetically it can be obtained by reduction of hexa-oxy-benzol. It is soluble in 7.5 parts of cold water, insoluble in strong alcohol and ether. It does not give the typical reduction reactions of carbohydrates, is not fermented; upon distillation with phosphoric anhydride it yields a certain amount of furfural. When a solution of I. is evaporated with nitric acid, the residue is moistened with ammonia and a solution of CaCl₂ and again evaporated, a pink coloration results (Scherer's inosit test); when evaporated with mercuric nitrate, a yellowish residue is obtained which acquires a bright red color upon heating (Gallois test). I. belongs to the nitrogen-free extractive substances, occurring besides muscle tissue where it was first discovered, in almost all other tissues and cells (liver, spleen, leukocytes, brain, normal and pathological urine, etc.). I. is widely distributed in the plant kingdom, occurring here both in free form (leaves, immature bean pods) and in the form of an ester with phosphoric acid - phytin. The biological significance of I. remains unclear, as well as its relationship to carbohydrates. The above-mentioned formation of furfural speaks to its closeness to carbohydrates; upon introduction of large amounts to an animal, lactic acid appears in the urine. In the animal body, I. apparently originates not only from I. and phytin of food, but can also be synthesized. It is also synthesized in the developing chicken embryo upon introduction of large amounts of glucose into the egg (Needham).