Бучу

The plant

Agathosma betulina is known by the common name round leaf buchu. It is a flowering plant native to the lower elevation mountains of western South Africa, where it occurs near streams in fynbos habitats. It is an evergreen shrub growing to 2 m tall. The leaves are opposite, rounded, about 20 mm long and broad, glossy, and fragrant. The flowers are white or pale pink, with five petals. The fruit is a five-parted capsule that splits open to release the seeds.

The very similar Agathosma crenulata is known as the oval leaf buchu and has been used for the same purposes. The two are chemically distinct, however: A. betulina contains quercetin-dimethyl ether-glucoside, while A. crenulata does not. Both species are endemic to the Western Cape mountains of South Africa and are cultivated on a commercial basis for their essential oils.

The genus

Agathosma is a genus of about 140 species of flowering plants in the family Rutaceae, native to the southern part of Africa. Common names of the genus include buchu, boegoe, bucco, bookoo and diosma. The genus name means "good fragrance". In colloquial use, the term buchu is applied to a wider set of fragrant shrubs or substitutes.

Chemistry

More than 120 components have been identified in buchu oil, among them pulegone, diosphenol and 8-mercapto-p-menthan-3-one. The two primary chemical constituents of the oils of A. betulina are isomenthone and diosphenol. Buchu is the only genus that produces diosphenol. 8-Mercapto-p-menthan-3-one is a sulphur-containing terpene responsible for the flavour and aroma of the oil.

Pulegone is the key component for identifying the oils of A. betulina, A. crenulata and their hybrids. A. betulina has a pulegone content of 2.4% to 4.5%, the hybrids have 7.6% to 27.8%, and A. crenulata has 31.6% to 73.2%. Two chemotypes of A. betulina have been described, depending on the diosphenol and isomenthone content. No chemotypes were found for A. crenulata. The isomenthone chemotype of A. betulina is restricted to the Piketberg mountain range.

Sourcing and uses

The essential oil of buchu is now used in food, cosmetics and pharmaceuticals. The essential oils and extracts of the leaves are used as flavoring for teas, candy, and a liquor known as buchu brandy in South Africa. Pharmacological experiments of the early 2000s were mostly carried out with hydro-distilled essential oils and/or methanol-dichloromethane extracts of both species. Buchu is an important source of local income for people in the region. The plant thrives in dry conditions and can be cultivated on hills where other crops do not do as well.

Wild plants of this species are still plentiful but are being harvested faster than they can reproduce. The threat of the wild plants becoming scarce has led to efforts to cultivate them. Companies using native biological resources such as buchu in research, product development and commercialisation need permits, as well as benefit sharing agreements.

History

The Khoi and San indigenous peoples used buchu for stomach ailments, as an antiseptic and mixed with animal fat for cosmetic applications. Dutch settlers in early times used Agathosma betulina to make a brandy tincture, and the tincture is still used today.

Bottled agathosma infusions were widely sold in English-speaking countries as "buchu tea" in the 1860s and 1870s. "Buchu vinegar" is a traditional remedy used for example in compresses and also taken internally. Its traditional use in urinary tract infections made buchu a popular remedy in the US in the 19th century, but with the advent of antibiotics it became largely obsolete.

In 1999, the Agricultural Research Council of South Africa initiated a project to cultivate buchu commercially to prevent it from becoming extinct.

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