The preparation of optically active isocitric acid from Bryophyllum leaf tissue.

d-Isocitric acid’ has, in recent years, attracted much interest as one of the organic acids concerned in reactions catalyzed by the enzymes of various animal and plant tissues. A demand has accordingly arisen for specimens of this rare substance for use in investigations of the enzyme systems involved. The fortunate observation that d-isocitric acid is present in the leaves of succulent plants of the family Crassulaceae in rather large proportions (5-7) suggested that a procedure could be developed whereby suitable preparations might be readily obtained. Such a procedure is described in the present communication. Preparation of Material-Two species, Bryophyllum fedtschenkoi and 3. calycinum, were used exclusively for the present work but other closely allied species would probably serve m well. B. caZycinum2 is commonly available in the greenhouses of university departments of botany, since the leaves are often used for demonstrations of the unusual manner of propagation of this plant; B. fedtschenkoi is less frequently found but has some advantage for the present purpose over B. calycinum, inasmuch as propa-