Origin and Production. The curcuma plant, Curcuma longa, L. (family Zingiberaceae), is indigenous to southern Asia and is cultivated in India, also in southern and eastern China because of the yellow pigment contained in the roots. Upon distillation with water vapor these roots yield 3 to 5,5 p.c. of a volatile oil.
Properties. Turmeric oil is an orange-yellow, slightly fluorescing liquid, the odor of which reminds one faintly of curcuma, and the specific gravity of which fluctuates between 0,942 and 0,961. The optical rotation of the oil varies. An oil distilled from old roots of unknown source had aD +22°2'; an oil from Madras roots, - 23°. When the optical rotation was re-determined after 7 and 4 years, respectively, the first showed aD +34°15'; the second, 18° 55'. Hence in both oils a decided increase of the dextro rotation was noticeable. A.V. 1,6 to 3,1; E.V. 7,8 to 16; E.V. after acetylation 30 to 53. With 1/2 to 1 vol. of 90 p.c. alcohol it yields a clear solution which occasionally becomes milky upon the addition of more alcohol.
1) Report of Schimmel & Co. October 1912, 87. 2) Americ. Journ. Pharm. 83 (1911), 2.
A turmeric oil distilled in the Philippines by F. Bacon 1) with a yield of 2,4 p.c. was soluble in all proportions in 75 p.c. or stronger alcohol; d30/30o 0,930; aD30o8,6° (+?); nD30o1,5030; E.V.81.
Composition. According to Bolley, Suida and Daube2), turmeric oil begins to boil at about 220°, and boils actively at 250°; later, decomposition sets in. Upon the addition of ammonium sulphide to fraction 230 to 250°, crystals separated which the investigators regarded as carvone hydrosulphide. F.A.Fluckiger3), however, obtained no hydrogen sulphide compound with any of the fractions, which proves the absence of carvone.
From roots exhausted with water and redried ). Kachler1) obtained by extraction with carbon disulphide 8 p.c. of a viscid oil which could not be saponified.
C. L. Jackson and A. E. Menke3), also Jackson and W. H. Warren6) examined an oil not obtained by steam distillation but by extraction with ligroin. Hence their product was always contaminated with petroleum hydrocarbons. After repeated fractionation in vacuo, they isolated, as principal constituent, an alcohol which they named turmerol and to which, according to analysis, either the formula C13H180 or C14H20O should be assigned. Turmerol has the following properties: b.p. 158 to 163° (11 to 12mm.); d24/4o 0,9561; [a] D + 24,58°. Hydrogen chloride or phosphorus trichloride converted it into a chloride, and sodium into a sodium derivative. The latter reacted with isobutyl iodide with the formation of an ether. Upon oxidation with dilute nitric acid, paratoluic acid resulted (m.p. 178°); with potassium permanganate, terephthalic acid.
1) Philippine Journ. of Sc. 5 (1910), A, 262.
2) Journ. f. prakt. Chem. 103 (1868), 474.
3) Berl. Berichte 9 (1876), 470.
4) Ibidem 3 (1870), 713.
5) Americ. chem. Journ. 4 (1882), 368; Pharmaceutical Journ. III. 18 (1883), 839; Chem. Zentralbl. 1883, 438.
6) Americ. chem. Journ. 18 (1896), 111; Chem. Zentralbl. 1896, I. 757.
When oxidized with chromic acid the products are very different. Thus Ivanow-Gajevsky1) obtained valeric and capronic acids from fraction 280 to 290°.
The latest investigations have been carried out by H.Rupe2) together with E. Luksch3), A. Steinbach and j. Burgin. They failed to obtain turmerol in a pure state, neither were they successful in preparing the sodium compound and ether, nor the chloride described by Jackson. In all instances the curcumone, to be described later, could be isolated after treatment with sodium, hydrogen chloride, or phosphorus trichloride. This curcumone, however, is not contained in the original oil. If the principal fraction of turmeric oil which, after repeated fractionation distils between 155 and 158° (11 mm.), is treated with acid or alkali, there results a ketone C13H180, the curcumone, an isomer of turmerol. For the preparation of this compound the oil itself may be used as starting point. 100 g. of curcuma oil are heated for 3 hours with an equal volume of alcohol and 30 p.c. potassium hydroxide solution in a flask connected with a reflux condenser. After cooling, the mixture is diluted with water and extracted 3 to 4 times with ether. The ethereal solution is washed with dilute phosphoric acid and dried over potassa. The crude ketone, boiling between 115 and 130° (10 mm.), is purified by means of the bisulphite addition product.
Curcumone is a colorless, not perfectly limpid oil with a penetrating, ginger-like odor, and has the following constants: b.p. 119 to 122° (8 to 11 mm.); d20o0,9566; [a]D20o + 80,55°; nD 1,50526; mol. refr. found 58,98, calculated 58,93. Of derivatives the following have been prepared: the oxime (b.p. 159° under 11 mm.), phenylhydrazone (m.p. 92°), p-bromophenylhydra-zone (m.p. 71°), benzylidene curcumone (m.p. 106°), piperonal curcumone (m.p. 113°), and the condensation product with anisic aldehyde (m.p. 77 to 78°).
1) Berl. Berichte 5 (1872), 1102.
2) Ibidem 40 (1907), 4909; 42 (1909), 2515; 44 (1911), 584, 1218.
3) E. Luksch, Uber Curcumaol. Inaug. Dissert., Basel 1906.
Upon oxidation of curcumone with potassium permanganate there resulted terephthalic acid (m.p. of the methyl ester 140°), p-tolylmethyl ketone (m. p. of semicarbazone 204 to 205° when heated very slowly), and p-acetyl benzoic acid (m.p. of benzyl-idene compound 232 to 233°). With hypobromous acid there resulted, in addition to bromoform, an acid which was volatile with water vapor and which was purified by means of its calcium salt. It revealed the following constants: m.p. 33 to 34°; b.p. 168 to 170° (12 mm.); [a]D20o + 31,15° (9,9 p.c. alcoholic solution). The acid named curcumic acid has the composition C12 H16 02 and results from the curcumone C13H180 upon oxidation of the Coch3 group to Cooh. The synthesis of 7-methyl-;'-/?-tolyl butyric acid and of p-tolylmethyl ethyl acetic acid have shown the non-identity of these two acids with curcumic acid.
In the residue obtained after steam distillation of curcumic acid there was contained a small amount of an acid which, after regeneration from its calcium salt, crystallized in large, shiny needles melting at 150 to 151°. It is probably a hydroxy-curcumic acid. When heated with permanganate solution it yields terephthalic acid.
When curcumic acid is oxidized with potassium permanganate, there results p-totyl methyl ketone, which is volatile with water vapor (m.p. of semicarbazone 204 to 205°). In the residue left after the steam distillation, the presence of a dicarboxylic acid, C12H1404, was established, melting at 226 to 228°.
The lowest fractions of turmeric oil contained d-a-phellan-drene1) (m.p. of nitrite 108°)2).