Studies on the Browning and Blackening of Plant Tissues. III Occurrence in the Leaves of Dahlia and Several Other Plants of Chlorogenic Acid as the Principal Browning Agent.

1. Leaves of Dahlia variabils, Aralia cordata, Clematis paniculata, Cryptotaenia japonica, Ilex latifolia, Inula salicina, Spiraea japonica var. ovatifolia, and Viburnum Sargentii contain among others chlorogenic acid as the agent, which gives rise to brown substance when subjected to oxidation by poly-phenoloxidase. Dahlia, Clematis, and Viburnum contain besides chlorogenic acid caffeic acid which is also oxidizable by this enzyme. The presence of these acids were detected by paper-chromatography. 2. Leaves of Aucuba japonica do not contain oxidase, although they contain chlorogenic acid. 3. Oxidation of chlorogenic acid by oxidase is inhibited to some extent by ascorbic acid. 4. In the leaves which had been allowed to stand at about 60° for oxidation for 5 minutes and become dark brown, chlorogenic acid and caffeic acid completely disappeared. 5. From leaves of Dablia citric acid and tyrosine were isolated. 6. In leaves which bad changed into dark brown and in which chlorogenic acid bad completely disappeared, glutamic acid almost completely disappeared and the quantity of alanine, which bad been present only in a small amount, considerably increased. [ABSTRACT FROM AUTHOR]