This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
The official buchu leaves are obtained from Barosma betulina, Bartling & Wendland (N.O. Butaceœ), a small shrubby plant indigenous to Cape Colony. The drug, the use of which appears to have been learnt from the Hottentots, was introduced in 1821 but this was probably not derived from the species now official. The branches, collected while the plant is flowering and fruiting, are dried, and beaten to separate the leaves which are exported from Cape Town.
Fig. 16. - Buchu leaves (B. betulina), showing the shape, margin, and recurved apex. Natural size.
The leaves of Barosma betulina, commercially known as 'short' buchu, average from 1 to 2 cm. in length, and are of a pale green colour. They have a very characteristic, rhomboid-obovate outline, and a blunt, strongly recurved apex. They are rigid and brittle when quite dry, but cartilaginous when moist. The surface is glabrous or very nearly so, short hairs being often present on the midrib near the base; the upper surface presents small wart-like prominences due to the elevation of the epidermis by subjacent oil-glands; the lower surface is finely wrinkled. The margin is provided with numerous, minute, sharp teeth. When examined with a lens by transmitted light the lamina exhibits scattered oil-glands, one being situated at the base of each marginal indentation.
The leaves have a characteristic odour recalling peppermint, and a strong aromatic taste.
The student should carefully observe
(a) The rhomboidal outline and recurved apex,
(b) The oil-glands and their distribution,
(c) The characteristic odour and taste; and should compare the official variety with the other commercial buchu leaves mentioned below, as well as with
Bearberry leaves, which are rounded at the apex, spathulate in outline, and destitute of oil-glands.
The principal constituents of buchu leaves are volatile oil and mucilage, the former being contained in the oil-glands, whilst the latter is deposited on the inner walls of the epidermal cells. They contain in addition a yellow crystalline substance, hesperidin, which is found in several other Rutaceous plants, but does not markedly contribute to the physiological action of the drug; this substance forms sphero-crystals in the epidermal cells. The volatile oil (1.3 to 2 per cent.) deposits about 30 per cent, of crystalline diosphenol, C10H16O2, when it is cooled. Diosphenol has antiseptic properties, and is considered by some to be the most important constituent of buchu; its absence from the variety known as long buchu has led to the exclusion of the latter from the British Pharmacopoeia. The oil also contains a ketone, probably identical with menthone, to which the peppermint-like odour is due.
Fig. 17. - Buchu leaves (B. serratifolia). Natural size.
Diosmin, which has been reported as a constituent of buchu, is probably impure hesperidin.
The leaves of this plant, which, like B. betulina, is also a native of South Africa, are imported in considerable quantity, and known commercially as ' long buchu.' They are about 2.5 to 4 cm. long and linear-lanceolate in outline. The margin is serrate, and the apex distinctly truncate.
The leaves contain oil-glands similar to those of short buchu, one being distinctly visible in the truncate apex when examined with a lens. In odour and taste they resemble short buchu; they contain mucilage and about 1 per cent, of volatile oil, which, however, as previously mentioned, does not yield diosphenol when cooled.
The leaves of this plant are also imported from the Cape of Good Hope, but in smaller quantity than either of the preceding varieties of the drug. They are rather broader than the long buchu, varying in outline from lanceolate to oval-oblong. The margin is minutely serrate, and the apex is blunt but not recurved (as in B. betulina). In odour and taste they resemble the official leaves; they yield about 1.6 per cent, of volatile oil, which also contains diosphenol.
Empleurum serrulatum, Aiton; resemble long buchu under which name they have been offered for sale; apex acute without oil gland, colour usually yellowish green, taste bitterish, odour different.
Fig. 18. - Buchu leaves (B. crenulata). Natural size.
Agathosma Cerefolium, Bartling and Wendland, A. microphylla, Meyer, A. variabilis, Sonder, have a distinct anise odour; A. chortopila, Ecklon and Zeyher, has a cummin odour.
B. Eckloniana, Bartling; rather broader than B. crenulata, more distantly crenate-serrate, apex very obtuse and without gland.
B. venusta, Ecklon and Zeyher; small, obovate or oblanceolate.
B. pulchella, Bartling and Zeyher; 7-12 mm. long, 5-8 mm. broad, ovate or ovate-lanceolate, margin thickened, apex obtuse, taste different.
B. ericifolia, Andr., B. succulenta, Thunberg; leaves heath-like, linear.
B. lanceolata, Sonder; rather narrower than B. crenulata, margin entire, recurved.
Psoralea obliqua, Meyer; lamina oblique, apiculus recurved, veins hairy.
Adenandra fragrans, Roemer and Schultes; oblong, obtuse, caraway odour.
Buchu is regarded as possessing a tonic and diuretic action; it is used in inflammatory conditions of the urinary tract.