_Concrete Oil of Mangosteen_, _Kokum Butter_.
=Botanical Origin.=—_Garcinia indica_ Choisy (_G. purpurea_ Roxb.
_Brindonia indica_ Dup. Th.), an elegant tree with drooping branches
and dark green leaves.[355] It bears a smooth round fruit the size of a
small apple, containing an acid purple pulp in which are lodged as many
as 8 seeds. The tree is a native of the coast region of Western India
known as the Concan, lying between Daman and Goa.
=History=—The fruit is mentioned by Garcia d’Orta(1563) as known to
the Portuguese of Goa by the name of _Brindones_. He states that it
has a pleasant taste though very sour, and that it is used in dyeing;
and further that the peel serves to make a sort of vinegar. Several
succeeding authors (as Bauchin and Ray) have contented themselves with
repeating this account.
As to the fruit yielding a fatty oil, we find no reference to such
fact till about the year 1830, when it was stated in an Indian
newspaper[356] that an oil of the seeds is well known at Goa and often
used to adulterate ghee (liquid butter). It was afterwards pointed out
as the result of some experiments that the oil was of an agreeable
bland taste and well adapted for use in pharmacy. A short article on
Kokum Butter was published by Pereira[357] in 1851. With the view of
bringing the substance into use for pharmaceutical preparations in
India, it has been introduced into the _Pharmacopœia of India_ of 1868.
[352] _Report from H. M. Consul-General in Siam for 1875_. 9.
[353] Spenser St. John, _op. cit._
[354] _Flora Sylvatica_, Madras, part xv. (1872) tab. 173.
[355] Fig. Bentley and Trimen, _Medic. Plants_, part 31 (1878).
[356] Quoted by Graham, _Catal. of Bombay Plants_, 1839. 25.
[357] _Pharm. Journ._ xi. (1852) 65.
=Preparation=—The seeds are reniform, somewhat crescent-shaped or
oblong, laterally compressed and wrinkled, ⁶/₁₀ to ⁸/₁₀ of an inch
long by about ⁴/₁₀ broad. Each seed weighs on an average about eight
grains. The thick cotyledons, which are inseparable,[358] have a mild
oily taste. Examination under the microscope shows them to be built
up of large reticulated cells containing a considerable proportion of
crystalline fat readily soluble in benzol. In addition globular masses
of albuminous matter occur which with iodine assume a brownish yellow
hue. With perchloride of iron the walls strike a greenish-black.
The process followed by the natives of India (by whom alone the oil
is prepared) has been thus described:—The seeds having been dried by
exposure for some days to the sun are bruised, and boiled in water. The
oil collects on the surface, and concretes when cool into a cake which
requires to be purified by melting and straining.
=Description=—Kokum Butter is found in the Indian bazaars in the form
of egg-shaped or oblong lumps about 4 inches long by 2 inches in
diameter, and weighing about a quarter of a pound. It is a whitish
substance, at ordinary temperatures, firm, dry, and friable, yet greasy
to the touch. Scrapings (which are even pulverulent) when examined in
glycerin under the microscope show it to be thoroughly crystalline.
They have a mild oily taste, yet redden litmus if moistened with
alcohol.
By filtration in a steam-bath, kokum butter is obtained perfectly
transparent and of a light straw-colour, concentrating again at 27·5°
C. into a white crystalline mass: some crystals appear even at 30°.
Melted in a narrow tube, cooled and then warmed in a water bath, the
fat begins to melt at 42·5 C., and fuses entirely at 45°. The residue
left after filtration of the crude fat is inconsiderable, and consists
chiefly of brown tannic matters soluble in spirit of wine.
When kokum butter is long kept it acquires an unpleasant rancid smell
and brownish hue, and an efflorescence of shining tufted crystals
appears on the surface of the mass.
=Chemical Composition=—Purified kokum butter boiled with caustic soda
yields a fine hard soap which, when decomposed with sulphuric acid,
affords a crystalline cake of fatty acids weighing as much as the
original fat. The acids were again combined with soda and the soap
having been decomposed, they were dissolved in alcohol of about 94
per cent. By slow cooling and evaporation crystals were first formed
which, when perfectly dried, melted at 69·5° C.: they are consequently
_Stearic Acid_. A less considerable amount of crystals which separated
subsequently had a fusing point of 55°, and may be referred to
_Myristic Acid_.
A portion of the crude fat was heated with oxide of lead and water,
and the plumbic compound dried and exhausted with ether, which after
evaporation left a very small amount of liquid oil, which we refer to
_Oleic Acid_.
Finally the sulphuric acid used at the outset of the experiments was
saturated and examined in the usual manner for volatile fatty acids
(butyric, valerianic, &c.) but with negative results.
[358] The embryo, according to Bentley and Trimen (_l. c._) consists
chiefly of the _thickened_ radicle, and is almost devoid of cotyledons.
The fat of the seeds of _G. indica_ was extracted by ether and examined
chemically in 1857 by J. Bouis and d’Oliveira Pimentel.[359] It was
obtained to the extent of 30 per cent., was found to fuse at 40° C. and
to consist chiefly of stearin (tristearin). The seeds yielded 1·72 per
cent. of nitrogen. Their residue after exhaustion by ether afforded to
alkaline solutions or alcohol a fine red colour.
=Uses=—The results of the experiments above-noted show that kokum
butter is well suited for some pharmaceutical preparations. It might
also be advantageously employed in candle-making, as it yields stearic
acid more easily and in a purer state than tallow and most other fats.
But that it is possible to obtain it in quantities sufficiently large
for important industrial uses, appears to us very problematical.