What is it?
An extract of the leaves of buchu, an evergreen shrub native to South Africa, listed on labels under its older name Barosma betulina; botanists now call it Agathosma betulina. Buchu belongs to the citrus family (Rutaceae), and its leaf oil, with a distinctive blackcurrant-like flavor, is used in perfumes and food flavorings. In cosmetics the extract is used for skin conditioning and fragrance.
Key information
- Buchu leaf oil contains pulegone, which made up 2.13 to 7.81 percent of batches analyzed for the European Food Safety Authority.
- IARC classifies pulegone as possibly carcinogenic to humans (Group 2B), based on animal studies.
- EFSA considers the concentrated buchu leaf oil a skin and eye irritant and a skin and respiratory sensitizer for people who handle it.
- Pulegone does not dissolve in water, so water-based buchu extracts are expected to contain little of it.
More information
The name buchu covers two South African shrubs, Agathosma betulina and A. crenulata. Buchu leaves were a popular remedy for urinary complaints in the 19th century, especially in the U.S., but that use faded with the arrival of antibiotics. Today buchu is valued mainly for its essential oil in perfumes and as a flavoring. It is the only genus that produces diosphenol, the compound behind its blackcurrant-like flavor.
Buchu leaf oil is steam-distilled from dried leaves. In batches analyzed for the European Food Safety Authority (EFSA), its main constituents were isomenthone, limonene and diosphenol, and it contained 2.13 to 7.81 percent pulegone, plus small amounts of menthofuran (0.22 to 0.37 percent) and methyleugenol (0.09 to 0.17 percent). The other species, A. crenulata, contains much more pulegone.
Pulegone is the main concern. At high doses it damages the liver, and buchu oils at high doses were toxic to the liver in rats. The U.S. National Toxicology Program found clear evidence that pulegone causes cancer in mice and female rats, and IARC classifies it as possibly carcinogenic to humans. The European Medicines Agency concluded that these effects have a threshold, occurring only at doses high enough to deplete the liver’s protective glutathione. EFSA found no concern for consumers from buchu oil used as a feed flavoring, but classed the concentrated oil as a skin and eye irritant and a skin and respiratory sensitizer for workers.
How much pulegone a cosmetic leaf extract contains depends on how it is made; because pulegone does not dissolve in water, water-based extracts should carry little. We found no safety assessment of buchu leaf extract by the Cosmetic Ingredient Review or the EU’s Scientific Committee on Consumer Safety. On labels it appears as Barosma Betulina Leaf Extract.
Sources: Frontiers in Pharmacology (2022): Buchu (Agathosma betulina and A. crenulata): rightfully forgotten or underutilized?; EFSA Journal (2022): Safety and efficacy of a feed additive consisting of an essential oil from the leaves of Agathosma betulina (buchu leaf oil) for all animal species
