_Baccæ Rhamni, Baccæ Spinæ cervinæ; Buckthorn Berries_; F. _Baies de
Neprun_; G. _Kreuzdornbeeren_.
=Botanical Origin=—_Rhamnus cathartica_ L., a robust diœcious shrub
with spreading branches, the smaller of which often terminate in a
stout thorn. It is indigenous to Northern Africa, the greater part of
Europe, and stretches eastward to the Caucasus and into Siberia. We
have seen stems 50 years old, having a diameter of 8 inches, sent from
the government of Cherson, Southern Russia. In England the buckthorn
though generally distributed is abundant only in certain districts;
in Scotland it occurs wild in but a single locality. Yet in Norway,
Sweden, and Finland it grows much further north.
The fruit which ripens in the autumn is collected for use chiefly in
the counties of Hertfordshire, Buckinghamshire, Oxfordshire, and also
from Wiltshire. The collectors usually prefer to supply the juice as
expressed by themselves.
=History=—The Buckthorn was well known to the Anglo-Saxons, and is
mentioned as _Hartsthorn_ or _Waythorn_ in their medical writings and
glossaries dating before the Norman conquest. The Welsh physicians of
Myddfai (“Meddygon Myddvai”) in the 13th century prescribed the juice
of the fruit of buckthorn boiled with honey as an aperient drink.
As _Spina Cervina_ the shrub is referred to by Piero de’ Crescenzi of
Bologna[643] about A.D. 1305.
[641] The analysis alluded to in the _Pharm. of India_ (p. 444)
concerns _Khaya_ (_Swietenia_) _senegalensis_, and not the present
species, as my friend Dr. Overbeck has informed me.—F. A. F.
[642] Beddome, _Flora Sylvatica_, Madras, part i. (1869) 8,—also
information communicated direct.
[643] _Trattato dall’ Agricoltura_, Milano, 1805, 10. iii. c. 58.
The medicinal use of the berries was familiar to all the writers on
botany and materia medica of the 16th century. Syrup of buckthorn first
appeared in the London Pharmacopœia of 1650; it was aromatized by means
of aniseed, cinnamon, mastich and nutmeg.
=Description=—The fruits, which are only used in the fresh state, are
small, juicy, spherical drupes the size of a pea, black and shining,
bearing on the summit the remnants of the style, and supported below
by a slender stalk expanded into a disc-like receptacle. Before
ripening the fruit is green and distinctly 4-lobed, afterwards smooth
and plump. It contains 4 one-seeded nuts[644] meeting at right angles
in the middle. The seed is erect with a broad furrow on the back: in
transverse section the albumen and cotyledons are seen to be curved
into a horseshoe form with the ends directed outwards.
The fresh juice is green, has an acid reaction and a sweetish,
afterwards disagreeably bitter taste, and repulsive odour. It is
coloured dingy green by ferric chloride, yellow by alkalis, red by
acids. According to Umney[645] it should have a sp. gr. of 1·070 to
1·075, but is seldom sold pure. By keeping the juice gradually turns
red.
=Microscopic Structure=—The epidermis consists of small tabular cells,
followed by a row of large cubic cells and then by several layers of
tangentially-extended cells rich in chlorophyll. This thick epicarp
passes into the loose thin-walled and large-celled sarocarp. Besides
chlorophyll it exhibits numerous cells each containing a kind of sac,
which may be squeezed out of the cell. These sacs are violet, turning
blue with alkalis. Similar, yet much more conspicuous bodies occur also
in the pulp of the Locust Bean (_Ceratonia Siliqua_ L.).
=Chemical Composition=—The berries of buckthorn and other species
of _Rhamnus_ contain interesting colouring matters, which have been
the subject of much chemical research and controversy. Winckler
in 1849 extracted from the juice _Rhamnocathartin_, a yellowish
uncrystallizable bitter substance, soluble in water but not in ether.
Alkalis colour it golden yellow; perchloride of iron, dark greenish
brown.
In 1840 Fleury, a pharmacien of Pontoise, discovered in buckthorn
juice a yellow substance forming cauliflower-like crystals to which
he gave the name of _Rhamnine_. This body has been recently studied
by Lefort,[646] who identified it with the _Rhamnetine_ of Galletly
(1858) and the _Chrysorhamnine_ of Schützenberger and Bertèche (1865).
Though obtainable from the berries of all kinds of _Rhamnus_ used in
dyeing (including the common buckthorn), it is got most easily and
abundantly from Persian Berries. When pure, and crystallized from
absolute alcohol, it is described as forming minute yellow translucent
tables. It is scarcely soluble in cold water, though colouring it pale
yellow; is soluble in hot alcohol, insoluble in ether or bisulphide of
carbon. It is very soluble in caustic alkalis, forming uncrystallizable
reddish-yellow solutions. From alkaline solutions it is precipitated
by a mineral acid in the form of a glutinous magma resembling hydrated
silica. Lefort assigns to it the formula C₁₂H₁₂O₅ + 2H₂O.
[644] In _Rh. Frangula_ L., the other British species, the fruit has 2
nuts.
[645] _Pharm. Journ._ Nov. 23 (1872) 404, and July 11 (1874) 21.
[646] _Sur les graines des Nerpruns tinctoriaux._—_Journ. de Pharm._
iv. (1866) 420.—See also the investigations of Liebermann and Hörmann,
1879.
This chemist has likewise found in the berries of _Rhamnus_, though
not with certainty in those of _R. cathartica_, a neutral substance
isomeric with rhamnine, to which he has given the name of _Rhamnegine_.
Unlike rhamnine it is very soluble in cold water, but in all other
respects it agrees with that body in chemical and physical properties.
The two substances have the same taste, almost the same tint, the same
crystalline form, and lastly they give rise to the same reactions with
chemical agents.
The conclusions of Lefort have been contested by Stein (1868) and by
Schützenberger (1868), the latter of whom succeeded in decomposing
rhamnegine and proving it a glucoside having the formula C₂₄H₃₂O₁₄. Its
decomposition gives rise to a body named _Rhamnetin_, C₁₂H₁₀O₅, and
a crystallizable sugar isomeric with mannite. Schützenberger admits
that the berries contain an isomeric modification of rhamnegine; but
in addition another colouring matter insoluble in water, which appears
to be the _Rhamnine_ of Lefort, but to which he assigns a different
formula, namely, C₁₈H₂₂O₁₀. This is also a glucoside capable of
being split into rhamnetin and a sugar. There are thus, according to
Schützenberger, two forms of rhamnegine which may be distinguished as α
and β, and there is the substance insoluble in water, named by Lefort
_Rhamnine_.
The question of the purgative principles of buckthorn, it will be
observed, has not been touched by all these researches.
=Uses=—From the juice of the berries is prepared a syrup having
strongly purgative properties, much more used as a medicine for animals
than for man. The pigment _Sap Green_ is also made from the juice.