NOTES ON THE ORGANIC ACIDS OF PYRUS CORONARIA, 

 RHUS GLABRA, AND ACER SACCHARUM 



By Charles K. Sando, Junior Chemist, Office of Plant Physiological and Fermentation 

 Investigations, Bureau of Plant Industry, United States Departjnent of Agriculture, 

 and H. H. BarTLETT, Collaborator, Office of Plant Physiological and Fermentation 

 Investigations, Bureau of Plant Industry, United States Department of Agriculture, 

 and Professor of Botany, University of Michigan 



During the study of other compounds found in the plants in question, 

 we have incidentally isolated and identified the organic acids of the 

 fruits of the wild American crab apple {Pyrus coronaria L.) and the 

 smooth sumac {Rhus glabra L-.). We have also made an examination of 

 the product known as " maple sand " (found to be impure calcium malate) 

 which is formed as a granular deposit in the pans during the process of 

 boiling down sap of the sugar maple {Acer saccharum Marsh.) to make 

 maple sirup. Every precise record of the distribution of plant products 

 is distinctly worth while, and rather than hold our data on the acids of 

 these three plants for incidental mention in papers dealing with other 

 matters, we have thrown them together in the following notes. 



OCCURRENCE OF MALIC ACID IN PYRUS CORONARIA, AND ITS 

 TRANSFORMATION INTO SUCCINIC ACID 



As might have been predicted from the botanical relationship of Pyrus 

 coroiiaria to the common apple, the very sour fruit of the American crab 

 apple was found to contain malic acid. It was also found that in water 

 extracts of this fruit, made without heat, there is a transformation of 

 malic into succinic acid, apparently through the action of enzyms of 

 the fruit itself. This discovery will be of no little interest if further in- 

 vestigations substantiate our belief that microorganisms were not con- 

 cerned in the process. 



Cold water extractions of crab apples collected near Ann Arbor, Mich., 

 were made in the presence of both chloroform and toluol, with the 

 expectation of obtaining solutions of the fruit acids free from pectin 

 and other colloidal substances. The extractions were made in large 

 stone jars, tightly packed with sliced fruits and filled to the top with 

 water saturated with chloroform and toluol. At the bottom there was 

 an excess of chloroform and at the top an excess of toluol. The solution 

 quickly became intensely sour. The extraction was allowed to take 

 place for several weeks, at the end of which time the apple tissues were 

 as green and hard as when collected, showing no change whatever in 

 appearance. The infusion was brown at the surface layer, but clear and 

 of a pale straw color below. Only the non-oxidized lower part of the 



Journal of Agricultural Research, Vol. XXJI, No. 4 



Washington, D. C. Oct. 22, 1921 



aad Key No. G-249 



(221) 



