_Kino_, _Gum Kino_, _East Indian Kino_; F. and G. _Kino_.
=Botanical Origin=—_Pterocarpus Marsupium_ Roxb., a handsome tree 40 to
80 feet high, frequent in the central and southern parts of the Indian
Peninsula and also in Ceylon, and affording a valuable timber. In the
Government forests of the Madras Presidency, it is one of the _reserved
trees_, the felling of which is placed under restrictions.
_Pt. indicus_ Willd., a tree of Southern India, the Malayan Peninsula
and the Indian and Philippine Islands, is capable of yielding kino, and
is the source of the small supplies of that drug that were formerly
shipped from Moulmein.
Several other plants afford substances bearing the name of _Kino_,
which will be noticed at the conclusion of the present article.
=History=—The introduction of kino into European medicine is due to
Fothergill, an eminent physician and patron of economic botany of
the last century. The drug which Fothergill examined was brought from
the river Gambia in West Africa as a rare sort of Dragon’s Blood, and
was described by him in 1757[766] under the name of _Gummi rubrum
astringens Gambiense_. It had been noticed at least twenty years before
as a production of the Gambia, by Moore, factor to the Royal African
Company, who says that the tree yielding it is called in the Mandingo
language _Kano_.[767] Specimens of this tree were sent to England in
1805 by the celebrated traveller Mungo Park, and recognized some years
later as identical with the _Pterocarpus erinaceus_ of Poiret.
It seems probable that African kino continued to reach England for some
years, for we find “_Gummi rubrum astringens_” regularly valued in the
stock of a London druggist[768] from 1776 to 1792.
Duncan in the _Edinburgh Dispensatory_ of 1803, while asserting
that “_kino is brought to us from Africa_,” admits that some, not
distinguishable from it, is imported from Jamaica. In a later edition
of the same work (1811), he says that the African drug is no longer
to be met with, and alludes to its place being supplied by other
kinds, as that of Jamaica, that imported by the East India Company,
and that of New South Wales derived from _Eucalyptus resinifera_ Sm.
It will thus be seen that at the commencement of the present century
several substances, produced in widely distant regions, bore the name
of _Kino_. That however which was principally used in the place of
the old African drug, was _East Indian_ Kino, the botanical origin of
which was shown by Wight and by Royle[769] (1844-46) to be _Pterocarpus
Marsupium_ Roxb.,—a tree which, curiously enough, is closely allied to
the kino tree of Tropical Africa.
This is the drug which is recognized as legitimate kino in all the
principal pharmacopœias of Europe. It appears to have been first
prepared for the European market in the early part of the present
century, on a plantation of the East India Company called Anjarakandy,
a few miles from Tellicherry on the Malabar Coast; but as we learn from
our friend Dr. Cleghorn, it was not grown there but on the ghats a
short distance inland.
=Extraction=—Kino is the juice of the tree, dried without artificial
heat.[770] As it exudes, it has the appearance of red currant
jelly, but hardens in a few hours after exposure to the air. In the
Government forests of the Malabar Coast whence the supplies are
obtained, permission to collect the drug is granted on payment of a
small fee, and on the understanding that the tapping is performed
skilfully and without damage to the timber. The method pursued is
this:—A perpendicular incision with lateral ones leading into it, is
made in the trunk, at the foot of which is placed a vessel to receive
the outflowing juice. This juice soon thickens, and when sufficiently
dried by exposure to the sun and air, is packed into wooden boxes for
exportation.
=Description=—Malabar kino[771] consists of dark, blackish-red,
angular fragments rarely larger than a pea, easily splitting into
still smaller pieces, which are seen to be perfectly transparent, of a
bright garnet hue, and amorphous under the microscope. In cold water
they sink, but partially dissolve by agitation, forming a solution
of very astringent taste, and a pale flocky residue. The latter is
taken up when the liquid is made to boil, and deposited on cooling in
a more voluminous form. Kino dissolves almost entirely in spirit of
wine (·838), affording a dark reddish solution, acid to litmus paper,
which by long keeping sometimes assumes a gelatinous condition. It is
readily soluble in solution of caustic alkali, and to a large extent in
a saturated solution of sugar.
[766] _Medical Observations and Inquiries_, i. (1757) 358.
[767] _Travels into the Inland Parts of Africa_, by Francis Moore,
Lond. 1737. pp. 160. 209. 267.
[768] J. Gurney Bevan, Plough Court, Lombard Street.—The drug was
priced in 1787 as having cost 16_s._, and in 1790-92, 21_s._ per lb.
[769] _Pharm. Journ._ v. (1846) 495.
[770] Cleghorn, _Forests and Gardens of South India_, 1861. 13.—Also
from information communicated by him orally.
[771] Our sample obtained from _Pt. Marsupium_ Roxb. on the Sigúr Ghat,
Feb. 1868, was kindly submitted to us by Mr. McIvor of Ootacamund.—We
find it to agree with commercial East Indian Kino.
=Chemical Composition=—Cold water forms with kino a reddish solution,
which is at first not altered if a fragment of ferrous sulphate is
added. But a violet colour is produced as soon as the liquid is
cautiously neutralized. This can be done by diluting it with common
water (containing bicarbonate of calcium) or by adding a drop of
solution of acetate of potassium. Yet the fact of kino developing an
intense violet colour in presence of a proto-salt of iron, may most
evidently be shown by shaking it with water, and iron reduced by
hydrogen. The filtered liquid is of a brilliant violet, and may be
evaporated at 100° without turning green; the dried residue even again
forms a violet solution with water. By long keeping the violet liquid
gelatinizes. It is decolorized by acids, and turns red on addition
of an alkali, whether caustic or bicarbonated. Catechu, as well as
crystallized catechin, show the same behaviour, but these solutions
quickly turn green on exposure to air.
Solutions of acids, of metallic salts, or of chromates produce copious
precipitates in an aqueous solution of kino. Ferric chloride forms a
dirty green precipitate, and is at the same time reduced to a ferrous
salt. Dilute mineral acids or alkalis do not occasion any decided
change of colour, but the former give rise to light brownish-red
precipitates of _Kino-tannic Acid_. By boiling for some time an aqueous
solution of kino-tannic acid, a red precipitate, _Kino-red_, is
separated.
Kino in its general behaviour is closely allied to Pegu catechu,
and yields by similar treatment the same products, that is to say,
it affords _Pyrocatechin_ when submitted to dry distillation, and
_Protocatechuic Acid_ together with _Phloroglucin_ when melted with
caustic soda or potash.
Yet in catechu the tannic acid is accompanied by a considerable amount
of catechin, which may be removed directly by exhaustion with ether.
Kino, on the other hand, yields to ether only a minute percentage
of a substance, whose scaly crystals display under the microscope
the character of _Pyrocatechin_, rather than that of catechin, which
crystallizes in prisms. The crystals extracted from kino dissolve
freely in cold water, which is not the case with catechin, and this
solution assumes a fine green if a very dilute solution of ferric
chloride is added, and turns red on addition of an alkali. This is the
behaviour of catechin as well as of pyrocatechin; but the difference
in solubility speaks in favour of the crystals afforded by kino being
pyrocatechin rather than catechin.
We thought pyrocatechin must also occur in the mother plant of kino,
but this does not prove to be the case, no indication of its presence
being perceptible either in the fresh bark or wood.[772]
Etti (1878) extracted from kino colourless prisms of _Kinoïn_ by
boiling the drug with twice its weight of hydrochloric acid, about 1·03
sp. gr. On cooling, kino-red separates, very little of it remaining in
solution together with kinoïn. The latter is extracted by exhausting
the liquid with ether, which by evaporation affords crystals of kinoïn.
They should be recrystallized from boiling water; they agree with the
formula C₁₄H₁₂O₆, which is to be regarded as that of a methylated
gallic ether of pyrocatechin, viz., C₆H₄ (OCH₃) C₇H₅O₅.
Kinoïn by heating it to 130° C. gives off water and turns red: