Chemistry of Essential Oils

$26 THE CHEMISTEY OF ESSENTIAL OILS

Jowefct and Pyman

l

found the oil to contain a phenol having the

odour of eugenol, free fatty acids, and a sesquiterpene having the follow-

ing values:—

Specific gravity. 0'897

Refractive index.. 1'4916

Optical rotation + 14-9°

CISTINE/E.

OIL OF LADANUM.

Ladanum or labdanum resin is a secretion from the leaves of several
species of Cistus, especially Cistus creticus and Cistus ladaniferus. Cistus
creticus is the Cretan rock rose, a native of rocky ground in Macedonia,
Thrace, Greece, and the islands of Crete, Bhodes, Sicily, and Cyprus.
Its botanical relationships are hardly decided, as it is regarded by some
as being merely a variety of Cistus villosus Linn. In Cyprus the
ladanum (labdanum) is chiefly collected by the shepherds from the
fleeces of the sheep, who unconsciously collect it from the plants whilst
pasturing, the leaves becoming very viscid with the secretion.
There seems to be a considerable amount of confusion as to the exact
botanical relationships of Cistus ladaniferus, but this has recently been
cleared up by E. M. Holmes^2 in dealing with the source of Spanish
ladanum. He finds that the plant used for collecting the oleo-resin in
Spain is Cistus ladaniferus, var. macellatus. There are about sixteen
species of Cistus known in Spain, and the name Cistus ladaniferus has
been applied by different botanists to at least four different species, so
that a few remarks on the distinctive characters of the true Cistus
ladaniferus may be useful.
The plant figured under this name in Curbis's Botanical Magazine,
tab. 1112, is Cistus Cyprius Lam. and is a native of Cyprus.
Cistus ladaniferus of Gouan is Cistus Ledon of Lamarch and the
Cistus glaucus of Poures, and is a native of the South of France.
Cistus ladaniferus of Stokes's Botanical Materia Medica, vol. iii., p.
209, is Cistus polymorphus Wilkoum, and the Cistus creticus of Limnoeus.
From all these the true Cistus ladaniferus of Limnoeus is distinguished
by the ovary having ten cells; in the other five only are present.
The true Cistus ladaniferus has been described in Stokes's Botanical
Materia Medica under the name of Cistus viscosus, and by Hoffmansegg
under the name of Cistus ladanosma.
The oleo-resin yields from 07 to 20 per cent, of essential oil having
the following characters:—

Boiling point 50° to 185° at 15 mm.

Specific gravity 0-928 to 1-011

Refractive index ....... 1-5100 „ 1-5140

On keeping the oil becomes oxidised somewhat rapidly and deposits a
considerable amount of crystals.
According to Masson,
3
the oil contains acetophenone, a compound
not hitherto found naturally occurring in essential oils; a second ketone
of the formula C 9 H 16 O, and having the following characters:—

(^1) Pharm. Jour., 91 (1913), 129.
2
3 P. andE.O.R. (1911), 155.
Comptes Rendus, 154 (1912), 517.