_Semen Ajavæ vel Ajouain_; _Ajowan_, _True Bishop’s weed_.
=Botanical Origin=—_Carum Ajowan_ Bentham et Hooker (_Ammi copticum_
L. _Ptychotis coptica_ et _Pt. Ajowan_ DC.)—an erect annual herb,
cultivated in Egypt and Persia, and especially in India where it is
well known as _Ajvan_ or _Omam_.
=History=—The minute spicy fruits of the above-named plant have been
used in India from a remote period, as we may infer from their being
mentioned in Sanskrit writings, as, for instance, by the grammarian
Pānini, in the third century B.C. (or later?), and in Susruta.
Owing to their having been confounded with some other very small
umbelliferous fruits, it is difficult to trace them precisely in many
of the older writers on materia medica. It is however probable that
they are the _Ammi_ which Anguillara[1154] met with in 1549 at Venice,
where it had then, exceptionally, been imported in small quantity from
Alexandria. It is also, we suppose, the _Ammi perpusillum_ of Lobel
(1571), in whose time the drug was likewise imported from Egypt, as
well as the _Ammi alterum parvum_, the seed of which Dodonæus (1583)
mentions as being “minutissimum, acre et fervidum.” Dale,[1155] who
says it is brought from Alexandria, reports it as very scarce in the
London shops. Under the name of _Ajave Seeds_, the drug was again
brought into notice in 1773 by Percival,[1156] who received a small
quantity of it from Malabar as a remedy for colic; and still more
recently, it has been favourably spoken of by Fleming, Ainslie,
Roxburgh, O’Shaughnessy, Waring and other writers who have treated of
Indian materia medica.
=Description=—Ajowan fruits, like those of other cultivated
_Umbelliferæ_, vary somewhat in size and form. The largest kind much
resemble those of parsley, being of about the same shape and weight.
The length of the large fruits is about ⅒, of the smaller form scarcely
¹/₁₆ of an inch. The fruits are greyish brown, plump, very rough on the
surface, owing to numerous minute tubercles (_fructus muriculatus_).
Each mericarp has five prominent ridges, the intervening channels being
dark brown, with a single vitta in each. The commissural side bears two
vittæ. The fruits when rubbed exhale a strong odour of thyme (_Thymus
vulgaris_ L.), and have a biting aromatic taste.
=Microscopic Structure=—The oil-ducts of ajowan are very large, often
attaining a diameter of 200 mkm. The ridges contain numerous spiral
vessels; the blunt tubercles of the epidermis are of the same structure
as those in anise, but comparatively larger and not pointed. The tissue
of the albumen exhibits numerous crystalloid granules of albuminous
matter (aleuron), distinctly observable in polarized light.
=Chemical Composition=—The fruits on an average afford from 4 to
4·5 per cent. of an agreeable aromatic, volatile oil; at the same
time there often collects on the surface of the distilled water a
crystalline substance, which is prepared at Oojein and elsewhere in
Central India, by exposing the oil to spontaneous evaporation at a low
temperature. This stearoptene, sold in the shops of Poona and other
places of the Deccan, under the name of _Ajwain-ka-phul_, i.e. _flowers
of ajwain_, was showed by Stenhouse (1855) and by Haines (1856) to be
identical with
{OH
Thymol, C₆H₃ {CH₃, as contained in Thymus vulgaris.
{C₃H₇
We obtained it by exposing oil of our own distillation, first rectified
from chloride of calcium, to a temperature of 0° C., when the oil
deposited 36 per cent. of thymol in superb tabular crystals, an inch
or more in length. The liquid portion, even after long exposure to a
cold some degrees below the freezing point, yielded no further crop.
We found the thymol thus obtained began to melt at 44° C., yet using
somewhat larger quantities, it appeared to require fully 51° C. for
complete fusion. On cooling, it continues fluid for a long time, and
only recrystallizes when a crystal of thymol is projected into it.
[1154] _Semplici_, Vinegia, 1561. 130.
[1155] _Pharmacologia_, 1693. 211.
[1156] _Essays, Medical and Experimental_, ii. (1773) 226.
Thymol is more conveniently and completely extracted from the oil by
shaking it repeatedly with caustic lye, and neutralizing the latter.
The oil of ajowan, from which the thymol has been removed, boils
at about 172°, and contains cymene (or cymol), C₁₀H₁₄, which, with
concentrated sulphuric acid, affords cymen-sulphonic acid, C₁₀H₁₃SO₂OH.
The latter is not very readily crystallizable, but forms crystallized
salts with baryum, calcium, zinc, lead, which are abundantly soluble
in water. In the oil of ajowan no constituent of the formula C₁₀H₁₆
appears to be present; mixed with alcohol and nitric acid (see p. 279)
it at least produces no crystals of terpin.
The residual portions of the oil, from which the cymene has been
distilled, contains another substance of the phenol class different
from thymol.
We have found that neither the thymol nor the liquid part of ajowan oil
possesses any rotatory power.
=Uses=—Ajowan is much used by the natives of India as a
condiment.[1157] The distilled water which has been introduced into
the _Pharmacopœia of India_, is reputed to be carminative, and a good
vehicle for nauseous medicines. It has a powerful burning taste, and
would seem to require dilution. The volatile oil may be used in the
place of oil of thyme, which it closely resembles.
Ajowan seeds are largely imported into Europe since thymol has been
universally introduced into medical practice (see Folia Thymi). They
have proved much more remunerative for the manufacture of thymol than
Thymus vulgaris. The largest quantities, we believe, of thymol have
been made from ajowan at Leipzig.
=Substitutes=—Under the name _Semen Ammi_, the very small fruits of
_Ammi majus_ L. and of _Sison Amomum_ L. have been often confounded
with those of Ajowan; but the _absence of hairs_ on the two former,
not to mention some other differences, is sufficient to negative any
supposition of identity.
The seeds of _Hyoscyamus niger_ L. being called in India
_Khorāsāniajwān_, a confusion might arise between them and true
ajowan; though the slightest examination would suffice to show the
difference.[1158]
[1157] Roxburgh, _Flor. Ind._ ii. (1832) 91.
[1158] To such a mistake may probably be referred the statement of
Irvine (_Account of the Mat. Med. of Patna_, 1848, p. 6) that the seeds
of henbane are “used in food as carminative and stimulant”!