On the Occurrence of Free-galacturonic Acid in Apples and Tomatoes.

Abstract

The fraction of the fresh fruit soluble in 70% 2-propanol was concentrated and the anions collected on an anion exchange resin (Duolite A-4). The anions were eluted with 20% formic acid and analyzed by paper chro-matography. Aniline-trichloracetate in glacial acetic acid was used as a dip reagent which gave fluorescent spots with glucuronic and man-nuronic acids, but not with galacturonic or guluronic. The single uronic acid found in all samples was identified as galacturonic on the basis of the above color test and co-chromatography. An unknown acid giving color tests for uronic acid, pentose, and hexose was found also in smaller amount in the apple samples. Quantitative analysis of the resin eluates, using the carbazole test for uronic acids, gave the following values for unripe, ripe, and overripe apples respectively: 4-12, 12, 390-470, ([mu]g/g fresh weight). Similar assays on tomatoes gave: 14, 140, 170.