Coloring matter occurring in various Juglandaceae spp: Brissemoret, Combes, Compt. Rend. 141, 838 (1905). Isoln from walnut shells: Combes, Bull. Soc. Chim. 1(4), 800 (1907). Isoln and description of sedative properties in fish, mammals: B. A. Westfall et al., Science 134, 1617 (1961). Isoln from pecans and identification as inhibitory agent of mycelial growth of Fusicladium effusum: P. A. Hedin et al., J. Agric. Food Chem. 28, 340 (1980). Synthesis: Bernthsen, Semper, Ber. 20, 938 (1887); Willsttter, Wheeler, Ber. 47, 2798 (1914); Teuber, Gtz, Ber. 87, 1236 (1954); C. Grundmann, Synthesis 1977, 644. Tumor-promoting activity study: B. L. Van Duuren et al., J. Med. Chem. 21, 26 (1978). Use as pH indicator: S. S. Sawhney, B. M. L. Bhatia, J. Indian Chem. Soc. 57, 438 (1980).