Combined Ascorbic Acid in Plant Tissues

Abstract

THE letter from Guha and Sen-Gupta recently published in NATURE¹ prompts us to give very briefly the results of some of our own experiments. The technique we have used is based on that described for urine². We find that in cauliflower juice (to quote one experiment) the total indophenol reducing substances amount to about 0·280 m.mol per 100 ml. Of this, free ascorbic acid accounts for some 0·007 m.mol, dehydroascorbic acid for 0·110 m.mol, and combined ascorbic acid (liberated by acid hydrolysis) for 0·150 mol. The non-ascorbic acid reducing substances are almost entirely in the combined form (liberated by acid hydrolysis) and amount to only 0·012 m.mol per 100 ml. of juice. The combined ascorbic acid is non-dialysable and is incompletely precipitated when the proteins are removed by metaphosphoric acid.