Upon distillation of the entire garlic plant, Allium sativum, L., (family Liliaceae) 0,005 to 0,009 p.c. of a volatile oil2) are obtained. It has a yellow color and possesses an intense, very unpleasant garlic odor: d15o 1,046 to 1,057; aD inactive.
As the result of a chemical investigation made in 1844, T. Wertheim5) arrived at the conclusion that garlic oil consists principally of allyl sulphide (C3H6)2S. For nearly 50 years this was the prevailing opinion and without re-examination it found its way into all of the text books.
When Semmler4) in 1892 re-examined the oil, it was found that garlic oil does not contain a trace of allyl sulphide5). In addition to carbon and hydrogen, the analysis of the oil revealed the presence of sulphur1), whereas oxygen and nitrogen were wanting.
1) H. Haensel, Chem. Zentralbl. 1908, I. 1837.
2) Schimmel's Bericht October 1889, 52; Report of Schimmel & Co. October 1890, 33.
3) Liebig's Annalen 51 (1844), 289.
4) Arch, der Pharm. 230 (1892), 434.
5) This also disposes of the statement that other oils, such as the oils of Thlaspi arvense, L. and Alliaria officinalis, L contain garlic oil or allyl-sulphide.
Inasmuch as the oil is decomposed by distillation under ordinary pressure it had to be distilled under diminished pressure. Under 16 mm. pressure it distilled over between 65 and 125°. Semmler isolated the following substances:
1. A disulphide C6H12S2 (abt. 6p.c.) which boils between 66 and 69° under 16 mm. pressure, and which presumably is an allyl-propyl disulphide, C3H5S.Sc3h7;
2. A disulphide C6 H10S2 (60 p. c.) constitutes the bulk of the oil and is the bearer of the pure garlic odor. B. p. 79 to 81° (16 mm.); d14,8o 1,0237. Its constitution is probably C3H5S.Sc3h6;
3. A substance C6H10S3 (20 p.c). B. p. 112 to 122° (16 mm.); d15o1,0845; constitutional formula C3H5S.S.S.C3H5.
The distillation residue reveals an even higher sulphur content and probably has the composition C6H10S4.
Inasmuch as allyl sulphide boils at 36 to 38° under 15,5 mm. pressure, and since the lowest fraction of garlic oil boils at 60 to 65°, the presence of allyl sulphide in the oil is excluded.
Neither was there a sesquiterpene in the oil examined by Semmler2).