3058
Vot. 64
COMMUNICATIONS T O T H E EDITOR THE TOXIC PRINCIPLES OF POISON IVY
an unsaturated acid (or acids, hydrogenation yielding a solid, m. p. 66-67’, depressed by palWe have investigated the active principles of mitic but not stearic acid; C, 73.4; H, 12.3; poison ivy and find that the toxic oil is a complex amide m. p. 1O5-10tio, depressed by palmitamide of a t least three active components and several but not stearamide; therefore stearic acid4) and a phenolic oil, log e 263 mp = 3.02, log E 273 mp = innocuous concomitants. 3.09 in absolute ethanol. In twenty-four hours Hill and his co-workers’ isolated a toxic yellow absorption decreased to log L 263 mp = 2.72 and oil from poison ivy with the stated boiling point the ferric chloride test became negative in the of 210’ (0.3 mm.), and presented evidence to original concentration, 0 mgm./100 cc. This sugprove that i t was identical with urushiol, the gests that the presence of drying oils in the boiling point of which was quoted as 210’ (0.4vesicant-bearing sap accounts a t least in part for 0.6 mm.). From this toxic oil they prepared a the extraordinary stability of the toxic prinseries of derivatives, identical when crystallizable ciples in their natural environment. with those prepared from urushiol, but no yields Chromatographed on alumina (Alorco) dewere reported. activated with (JOY0 ethanol, fraction l yielded “Urushiol” is a name first applied by Majima2 six bands, from the top: orange, four colorless to an extract of Japan lac which boiled over a with bright blue-white fluorescence under ultrarange of 210-222’ ((0.4-0.6 mni.), and, upon violet light, and yellow. One fluorescent band, redistillation, from 195’ to “above 2 1 0 O . ” It eluted with 90% ethanol, was phenolic and autowas shown to consist of four components3 the oxidized with extreme rapidity. The other structures of which were partially elucidated. Since i t is known that plants of the Anacardia- fluorescent bands could not be removed without ceae family, t o which both poison ivy and Japan major destruction, but were shown to be highly lac belong, elaborate a number of vesicant mono- toxic, while the remaining fractions were not. and dihydric alkyl phenols with fifteen and We conclude that a t least three toxic components seventeen carbon side chains, the derivatives are present, and are engaged in improving this prepared by Hill only prove the presence of a technique and elucidating the structures of the compound or compounds with R 3-pentadeca- toxic compounds. The exigencies of the day have catechol skeleton in the distillate. This is a required this short report a t this time. (.:I We are indebtcd t o Dr. k t h l l r T. Ness for the microchernicdl property it possesses in common with urushiol. analyaea. Essentially we followed Hill’s method of isolaSECTION OF DERMATOSES INVESTIGATIONS tion; our concentrate boiled over a range, the DIVISIONOF INDUSTRIAL HYGIENE INSTITUTE OF HEALTH HOWARD S. MASON major portion distilling a t 185-250’ (2 microns) NATIONAL BETHESDA, MARYLAKD LOUISSCHWARTZ with considerable resinification. Kedistillatioti RECEIVED OCTOBER 21, 1942 in a Hickman molecular still yielded three frac-_________ tions a t bath temperatures up to 12;i”, 1fi.S‘ and THE MECHANISM OF THE DIELS-ALDER 170’, the principal superficial difference being one REACTION of color. The products, although containing Sir: innocuous concomitants, were all toxic, 0.5 I t is noteworthy that in the usual case the Dielsgamma of oil per sq. cm. of hypersensitive skin Alder reaction involves, on the one hand, a subbeing sufficient to elicit a strong characteristic stance, e . g., a diene, of relatively low ionization poison ivy reaction. potential and, on the other, a molecule of high Chromatographed under nitrogen on barium electron affinity, e. g., an a,B-unsaturated carcarbonate--Hyflo Super Cel (Johns Mansville bonyl compound. We may therefore expect an Sales Corporation7, fraction 1 was separated into electron-transfer from the diene to the dienophile 1 1 13111, hIdttacUtt1 dlld Graham, ’1 H I S J O U R ~ A I . . 66, 27J(b (1‘)-
