Bound Ascorbic Acid in Liver

THE existence of bound ascorbic acid in pork liver was reported by Sumerwell and Sealock 1 . Their method was, however, criticized by Lewis, Chiang and Gross 2 . In my search for the existence of bound ascorbic acid in different animal tissues, goat liver was studied in the present investigation. Liver was brought to the laboratory direct from the slaughter-house in a ‘Cellophane’ bag in a ‘Thermos’-flask containing ice. It was then disintegrated in a previously cooled Waring blender with cold 95 per cent ethanol saturated with carbon dioxide and centrifuged. The residue was similarly extracted twice again and all the extracts were mixed. An aliquot of this mixture was titrated with 2: 6-dichlorophenol indophenol and another aliquot was heated on a boiling water-bath for 10 min with metaphosphoric acid (5 per cent) in an atmosphere of carbon dioxide, cooled, made to a definite volume and titrated with the indophenol dye. The former would give the quantity of free ascorbic acid and the latter of total ascorbic acid. The difference in the two values would give the quantity of bound ascorbic acid, which releases ascorbic acid on hydrolysis. Total ascorbic acid was also determined for comparison by Roe and Kuether's method. Results are given in Table 1.