Studies on Carbohydrate Metabolism

Previous studies of carbohydrate metabolism have been limited almost exclusively to naturally occurring saturated sugars. Very little attention has been devoted to the fate of the unsaturated and anhydro sugars in the organism. Even though these unsaturated sugars occur very rarely in nature, information concerning their fate in the body would be of value in determining the mechanism of sugar metabolism. Winter (1) reported that glucal injected into hypoglycemic rabbits relieves insulin convulsions, rebalancing the blood sugar level within a short period of time. The close chemical relation between glucal and 2-glucodesose led Winter (2) to a study of the physiological behavior of the latter substance. It proved, however, to be inactive. Kondo (3) showed that glucal after subcutaneous or oral administration was excreted by the rabbit in the urine in the form of 2-glucodesose. 2-Glucodesose itself after being given to rabbits was excreted unchanged. Only 2 to 3 per cent could be recovered from the urine as 2-glucodesose-pnitrophenylhydrazone. With the exception of a study on the physiological action of cr-glucosan (4) no other work has been done on unsaturated and anhydro sugars in respect to their physiological significance. The great chemical reactivity of glucal as a representative unsaturated sugar is illustrated by (I) to (V). Oxidation leads to d-mannose (II) and eventually to d-glucose (III) ; reduction to hydroglucal (IV) ; addition of water finally to 2-glucodesose (V).