Studies on Essential Oil of Sea Weeds-III
The Constituents of the Oil of Dictyota dichotoma
1953 Volume 19 Issue 6 Pages 717-721
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1953 Volume 19 Issue 6 Pages 717-721
The brown alga, Dictyota dichotoma gives on steam distillation a viscous oil of yellowish brown tinge with peculiar beach smell. The constituents of this oil were studied by the author with the following results
I) The acidic part. Free acids were divided into solid and liquid acids in the proportion of 46% to 54% by means of the alcoholic-lead method. Palmitic acid was isolated from the solid acids. The liquid acids, upon addition of bromine, converted into the bromides soluble in ether and also in petroleum ether. The debrominated acids yielded dihydroxypalmitic acid on oxidation by Hazura's method, therefore, the original acids is presumed to consist mainly of hexadecenoic acid.
II) The neutral part. Neutral oil obtained after removal of free acids consisted chiefly of sesquiterpene and sesquiterpene alcohol, and in addition to them, it contained a small quantity of normal paraffines.
1. n-Paraffines By employing the method of forming complexes with urea, two kinds of n-paraffines were obtained, namely, the liquid paraffin freezing at -10°C and the crystalline one melting at 41-2°C.
2. Sesquiterpene On fractional distillation of the neutral oil after removal of n-paraffines, the sesquiterpenic fraction with b. p. 147-153°C/4.5mm. was obtained. On its dehydrogenation with selenium, 1.6-dimethylnapatalene which converted into picrate, m. p. 110-111°C, and a large quantity of liquid giving no picrate were produced.
3. Sesquiterpene alcohol The fraction with b. p. 160-170°C/3.5mm. was proved to correspond to a tirtialy sesquiterpene alcohol. On its dehyerogenation, the same products as in the case of sesquiteroene were obtained. and in addition to them, a blue azulene and the needle crystalline with m.p. 127-8°C giving no picrate were also produced.
In view of the results of dehydrogenation, those sesquiterpenic compounds are presumed to be not of cadalene-type, but to have a constitution closely connected with the occurrence of 1.6-dimethylnaphthalene, and the fraction of sesquiterpene alcohol is probably mixtures of azulene-type and non-cadalene-type.
