Oxidatire Breakdown of Hyaluronic and Chondroitin Sulphuric Acid.

Abstract

Summary. The viscosity of hyaluronic acid solutions is markedly reduced by ascorbic acid in the presence of atmospheric oxygen. Cu++ highly increases this effect, which is on the other hand completely inhibited by diethyldithiocarbamate, or cyanide. Catalase does not inhibite the action of ascorbic acid. Dehydroascorbic acid obtained by oxidation of ascorbic acid with molecular oxygen + Cu++ has, under aerobic conditions, the same effect as ascorbic acid + Cu++. The effect of ascorbic acid is also greatly increased by hydrogen peroxide, which itself although relatively slowly, reduces the viscosity of hyaluronic acid solutions. In the presence of hydrogen peroxide the ascorbic acid is also active anaerobically. The mechanism of the action of ascorbic acid is discussed. A viscosity decreasing effect is brought about also by molecular oxygen (at + 100° C), potassium permanganate, and, in the presence of atmospheric oxygen, by hydroquinone, pyrogallol and cysteine + Cu++. The effect of oxygen is inhibited by diethyl‐dithiocarbamate and cyanide. The products formed from hyaluronic acid during its oxidative breakdown are non‐reducing and dialysable. The decrease of the viscosity is accompanied by the disappearance of the double refraction of flow shown by the native hyaluronic acid solution. The oxidative depolymerisation of hyaluronic acid is connected with the formation of titratable acid groups in an amount approximately corresponding to one carboxylic group for each disaccharide unit of glucuronic acid and N‐acetylglucosamine. Determinations of glucosamine and glucuronic acid in the solution of the dissociated products suggest that the main reaction product might be a “disaccharide” of glucuronic acid and N‐acetylglucosaminic acid. Chondroitin sulphuric acid is broken down in the same way as hyaluronic acid by ascorbic acid and hydrogen peroxide. The reaction is, however, slower and does not proceed as far as that of hyaluronic acid under the experimental conditions employed. Heparin, starch and cellulose could be similarly broken down to some extent by ascorbic acid.