From leaves of Ampelopsis meliaefolia Kudo, Vitaceae: Kotake, Kubota, Ann. 544, 253 (1940); from bark of Pinus contoria Dougl., Pinaceae: Hergert, J. Org. Chem. 21, 534 (1956); US 2870165 (1959 to Rayonier); from Erythrophleum africanum (Welw.) Harms, Caesalpiniaceae: Hansel, Klaffenbach, Arch. Pharm. 294, 158 (1961). Synthesis from myricetin, q.v.: Kotake, Kubota, J. Inst. Polytech. Osaka City Univ. 1, no. 2, 47 (1950), C.A. 46, 2052e (1952).