A tannin from the Indian gooseberry ( Phyllanthus emblica ) with a protective action on ascorbic acid

Abstract

IN a communication on the ascorbic acid content of Indian plant materials [Damodaran and Srinivasan, 1935], attention was drawn to the fact that different plant juices showed marked variations in the rate of oxidation of the ascorbic acid present in them. As a striking instance mention was made of the fruit of the Indian gooseberry (Phyllanthus emblica), which according to the Tillmans-Harris titration method had an ascorbic acid content of about 4-6 mg. per g. of the material. The undiluted press-juice of this fruit was extremely resistant to atmospheric oxidation and, in contrast to most other plant juices which rapidly deteriorated in their ascorbic acid content on standing, retained its titre undiminished even after a week's exposure to the air. The suggestion was therefore made that Phylktnthus emblica possibly contained some mechanism which prevented or retarded the oxidation of ascorbic acid. Further evidence for this view was found in the fact that in the gooseberry a considerable proportion of the ascorbic acid remained unaffected even when the fruits were dried. The existence of such a protective mechanism in animal tissues has been demonstrated by Mawson [1935] who, however, could find no evidence of its counterpart in plants. The distinguishing characteristics of the gooseberry press-juice in comparison with most other plant juices examined were a strong acid reaction and the presence of a large amount of tannin substances with characteristic colour reactions, which were not quantitatively precipitated from solution by normal lead acetate, but which could be completely removed by means of mercuric acetate.