1. _Barosma crenulata_ Hook. (_B. crenata_ Kunze).—Oblong, oval, or
obovate, obtuse, narrowed towards the base into a distinct petiole;
margin serrulate or crenulate; dimensions, ¾ to 1½ inches long, ³/₁₀ to
⁴/₁₀ of an inch wide.
2. _B. serratifolia_ Willd.—Linear-lanceolate, equally narrowed towards
either end, three-nerved, apex truncate always furnished with an
oil-cell; margin sharply serrulate; 1-1½ inches long by about ²/₁₀ of
an inch wide.
3. _B. betulina_ Bartling.—Cuneate-obovate, apex recurved; margin
sharply denticulate, teeth spreading; ½ to ¾ of an inch long by ³/₁₀
to ⁵/₁₀ wide. Substance of the leaf more harsh and rigid than in the
preceding.
_B. crenulata_ and _B. betulina_ grow in the Divisions of Clanwilliam
and Worcester, north and north-east of Cape Town, and the former even
on Table Mountain close to the capital; _B. serratifolia_ is found in
the Division of Swellendam farther south.
=History=—The use of Buchu leaves was learnt from the Hottentots by the
colonists of the Cape of Good Hope. The first importations of the drug
were consigned to the house of Reece & Co., of London, who introduced
it to the medical profession in 1821.[428] The species appears to have
been _B. crenulata_.
=Description=—In addition to the characters already pointed out, we may
observe that buchu leaves of either of the kinds mentioned are smooth
and glabrous, of a dull yellowish-green hue, somewhat paler on the
under side, on which oil-cells in considerable number are perceptible.
[426] _Am. Journ. of Pharm._ 1874. 50; also _Yearbook of Pharm._ 1874.
91.
[427] From βαρὺς, _heavy_, and ὀσμὴ, _odour_.
[428] R. Reece, _Monthly Gazette of Health_ for Feb. 1821. 799.
The leaves of _B. crenulata_ vary in shape and size in different
parcels, in some the leaves being larger and more elongated than
in others, probably according to the luxuriance of the bushes in
particular localities. Those of _B. serratifolia_ and _B. betulina_
present but little variation. Each kind is always imported by itself.
Those of _B. betulina_ are the least esteemed, and fetch a lower price
than the others, yet appear to be quite as rich in essential oil.
Buchu leaves have a penetrating peculiar odour and a strongly aromatic
taste.
=Microscopic Structure=—The essential oil is contained in large
cells close beneath the epidermis of the under side of the leaf. The
oil-cells are circular and surrounded by a thin layer of smaller cells;
they consequently partake of the character of the oil-ducts in the
aromatic roots of _Umbelliferæ_ and _Compositæ_. The latter, however,
are elongated.
The upper side of the leaf of _Barosma_ exhibits an extremely
interesting peculiarity[429]. There is a colourless layer of cells
separating the epidermis from the green inner tissue (mesophyllum).
If the leaves are examined under alcohol or almond oil the colourless
layer is seen to be very narrow, and the thin walls of its cells
shrunken and not clearly distinguishable. If the transverse sections
are examined under water, these cells immediately swell up, and become
strongly distended, giving off an abundance of mucilage, the latter
being afforded by the solution of the very cell-walls. The mucilage of
buchu leaves thus originates in the same way as in flax seed or quince
seed, but in the former the epidermis is thrown off without alteration.
We are not aware that other mucilaginous leaves possess a similar
structure, at least not those of _Althæa officinalis_ and of _Sesamum_
which we examined[430].
=Chemical Composition=—The leaves of _B. betulina_ afforded us by
distillation 1·56 per cent, of volatile oil[431], which has the odour
rather of peppermint than of buchu, and deviates the ray of polarized
light considerably to the left. On exposure to cold it furnishes a
camphor which, after re-solution in spirit of wine, crystallizes in
needle-shaped forms. After repeated purification in this manner, the
crystals of _Barosma Camphor_ have an almost pure peppermint odour;
they fuse at 85° C., and begin to sublime at 110° C. After fusion
they again solidify only at 50° C. Submitted to elementary analysis,
the crystals yielded us 74·08 per cent. of carbon and from 9 to 10
per cent. of hydrogen[432]. Barosma camphor is abundantly soluble in
bisulphide of carbon.
The crude oil from which the camphor has been separated has a boiling
point of about 200° C., quickly rising to 210° or even higher. That
which distilled between these temperatures was treated with sodium,
rectified in a current of common coal gas and submitted to elementary
analysis, afforded us 77·86 per cent, of carbon and 10·58 of hydrogen.
The formula C₁₀H₁₆O would require 78·94 of carbon and 10·53 of hydrogen.
Wayne’s experiments[433] appear to indicate that the oil also contains
a substance capable of being converted into _salicylic acid_. An
aqueous infusion of buchu leaves turns beautifully yellow if it is
mixed with alkali.
[429] Flückiger in _Schweiz. Wochenschrift für Pharm._ Dec. 1873, with
plate.
[430] See also Radlkofer, _Monographie der Sapindaceen-Gattung
Serjania_, München, 1875, p. 100-105.
[431] Messrs. Allen and Hanburys operating on larger quantities
obtained 1.63 per cent.—_Barosma serratifolia_ appears to be less rich,
according to Bedford (1863).
[432] Our supply of the substance having been exhausted by two analyses
we cannot regard the above figures as sufficient for the calculation of
a formula.
[433] _Am. Journ. of Pharm._ 1876. 19.
On addition of perchloride of iron the infusion assumes a dingy
brownish-green colour changing to red by an alkali. The infusion
added to a concentrated solution of acetate of copper causes a yellow
precipitate[434] which dissolves in caustic potash, affording a green
solution. This may be due to the presence of a substance of the
quercitrin or rutin class.
When the leaves are infused in warm water, the mucilage noticed under
the microscope may easily be pressed out. It requires for precipitation
a large amount of alcohol, being readily miscible with dilute alcohol.
Neutral acetate of lead produces a yellow precipitate in an infusion of
the leaves; the liquid affords a precipitate by a subsequent addition
of _basic_ acetate of lead. The latter precipitate is (probably) due to
the mucilage, that afforded by neutral acetate partly to mucilage and
partly, we suppose, to rutin or an allied substance. Yet the mucilage
of buchu leaves is of the class which is not properly dissolved by
water, but only swells up like tragacanth.
The leaves of _B. crenulata_ afforded us upon incineration 4·7 per
cent. of ash. Jones (1879) obtained on an average 4·54 per cent. from
the same species; 5·27 from _B. serratifolia_; and 4·49 from _B.
betulina_. He pointed out the presence of manganate in this ash.
The _Diosmin_ of Landerer[435] is entirely unknown to us.
=Commerce=—The export of buchu from the Cape Colony in 1872 was 379,125
lb., about one-sixth of which quantity was shipped direct to the United
States.[436]
=Uses=—Buchu is principally administered in disorders of the
urino-genital organs. It is reputed diuretic and diaphoretic. In
the Cape Colony the leaves are much employed as a popular stimulant
and stomachic, infused in water, sherry, or brandy. They are also
extensively used in the United States, both in regular medicine and by
the vendors of secret remedies.
=Substitutes=—The leaves of _Empleurum serrulatum_ Ait., a small shrub
of the same order as _Barosma_ and growing in the same localities,
have been imported rather frequently of late and sold as _Buchu_. They
have the same structure as regards mucilage, and nearly the same form
as those of _B. serratifolia_, but are easily distinguished. They are
still narrower, and often longer than those of _B. serratifolia_,
devoid of lateral veins, and terminate in an _acute_ point _without an
oil-duct_. They have a bitterish taste and a less powerful odour than
those of Barosma, even in fresh leaves as imported in London. The odour
of _Empleurum_ is moreover distinctly different from that of the leaves
of Barosma. The flowers of _Empleurum_ are still more distinct, for
they are apetalous and reddish-brown. The fruit consisting of a single,
compressed, oblong carpel, terminated by a flat-shaped horn, is quite
unlike that of buchu.
The leaves of _Barosma Eckloniana_ Berg (regarded by Sonder[437] as
a form of _B. crenulata_) have to our knowledge been imported on one
occasion (1873). They are nearly an inch long, oval, _rounded at the
base_, strongly crenate, and grow from _pubescent_ shoots.
[434] It seems _green_ as long as it is in the blue cupric liquid.
[435] Gmelin’s _Chemistry_, xviii 194.
[436] _Blue Book_ published at Cape Town, 1873.
[437] Harvey and Sonder, _Flora Capensis_, i. (1859-60) 393.
We have seen other leaves which had been imported from South Africa and
offered as buchu; but though probably derived from allied genera they
were not to be mistaken for the genuine drug.