Buchu

The Khoi and San peoples of the southwestern Cape used buchu for everyday, ritual and medicinal purposes. They applied the name to several strongly aromatic plants, not to one species ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

The dried leaf was powdered, mixed with fat and rubbed on the body as an anointment and perfume, and it was used in dance rituals ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}. An early eighteenth-century account describes the dried, powdered leaf used for aches ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

As a medicine it was taken for kidney and urinary tract infections, colds, stomach ailments, rheumatism, gout and fever. Externally, leaves steeped in brandy or vinegar were applied to wounds, bruises, sprains and swelling ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

Buchu was also combined with other plants. One such mixture traded in Cape Town, built on the related A. crenulata with Dodonaea viscosa and Eucalyptus globulus, was stronger against bacteria than any of its herbs alone ^{7Reference 7Zonyane S et al. · 2013In vitroAntimicrobial interactions of Khoi-San poly-herbal remedies with emphasis on the combination Agathosma crenulata, Dodonaea viscosa and Eucalyptus globulus — in vitro studyView study →}.

Buchu entered European medicine in the early nineteenth century. It was listed in the Dublin pharmacopoeia in 1826 for its diuretic effect and for genito-urinary infections, and it spread through most European pharmacopoeias ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

Nineteenth-century writers added uses for gout, rheumatism, poor appetite and oedema ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}. The Eclectic physicians also used it as an aromatic stimulant for poor appetite, flatulence and nausea ^{2Reference 2Moolla A · 2008ReviewMoolla A, Viljoen AM. (2008). ‘Buchu’ — Agathosma betulina and Agathosma crenulata (Rutaceae): a review. J Ethnopharmacol. https://pubmed.ncbi.nlm.nih.gov/18725278/View study →}.

In the United States it became one of the best-selling patent medicines of the 1860s ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}. It left the mainstream pharmacopoeias in the twentieth century, once antibiotics replaced it, but it stayed in the British Herbal Pharmacopoeia ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

The leaf is taken as an infusion or tincture for cystitis, urethritis and prostatitis ^{2,3Reference 2Moolla A · 2008ReviewMoolla A, Viljoen AM. (2008). ‘Buchu’ — Agathosma betulina and Agathosma crenulata (Rutaceae): a review. J Ethnopharmacol. https://pubmed.ncbi.nlm.nih.gov/18725278/View study →Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}. Its oil is also used as a blackcurrant flavouring in foods and in perfumery ^{3,11Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →Reference 11Cohen SM et al. · 2020ReviewFEMA GRAS assessment of natural flavor complexes: mint, buchu, dill and caraway derived flavoring ingredients — reviewView study →}.

The essential oil relaxed guinea-pig ileum in vitro. At high concentration it first contracted the muscle and then relaxed it, and the relaxant effect was post-synaptic, not atropine-like, and independent of adrenoceptors or guanylyl cyclase ^{1Reference 1Lis-Balchin M et al. · 2001In vitroBuchu (Agathosma betulina and A. crenulata, Rutaceae) essential oils: their pharmacological action on guinea-pig ileum and antimicrobial activity on microorganisms — in vitro studyView study →}.

The phosphodiesterase inhibitor rolipram increased the effect, pointing to a cyclic-AMP mechanism, and A. betulina oil also appeared to block calcium channels ^{1Reference 1Lis-Balchin M et al. · 2001In vitroBuchu (Agathosma betulina and A. crenulata, Rutaceae) essential oils: their pharmacological action on guinea-pig ileum and antimicrobial activity on microorganisms — in vitro studyView study →}.

The tissue was gut smooth muscle, not bladder or ureter, and the study was a single in vitro experiment.

Increasing urine flow is buchu’s defining traditional use, and it was the basis of its pharmacopoeial listing from 1826 ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}. No controlled study in animals or people has measured a diuretic effect ^{2,3Reference 2Moolla A · 2008ReviewMoolla A, Viljoen AM. (2008). ‘Buchu’ — Agathosma betulina and Agathosma crenulata (Rutaceae): a review. J Ethnopharmacol. https://pubmed.ncbi.nlm.nih.gov/18725278/View study →Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

The explanation usually given is that buchu raises blood flow through the kidneys rather than acting on salt handling in the tubules. This has not been tested for buchu.

Gap: there is no urine-output or kidney-filtration data for buchu in any species.

A commercial “buchu water” — the water left over from steam-distilling the oil, then concentrated — was tested in cells and rats ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}. In fat cells it raised glucose uptake by 35–40%, similar to insulin; in liver cells only the pure oil raised glucose uptake, by 12–21% ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

In rats with chemically induced diabetes, drinking the extract for 14 weeks normalised blood glucose where it had been below 20 mmol/L and lowered it where it was higher ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}. In rats on a high-fat diet it reduced weight gain and abdominal fat, and brought raised blood pressure back to normal ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

The flavonoids in the extract were present only in trace amounts, and the active compounds were not identified ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

A 2025 computer-modelling study predicted that γ-diosphenol and linalyl anthranilate from the oil bind PTP1B, a diabetes target ^{4Reference 4Adedirin O et al. · 2025Density functional theory and molecular dynamics simulation-based bioprospection of Agathosma betulina essential oil metabolites against protein tyrosine phosphatase 1B — in silico studyView study →}. A 2026 study found that the oil inhibited PTP1B and DPP4 in enzyme assays, and modelled two quercetin glycosides from the leaf as binders ^{5Reference 5Adedirin O · 2026In vitroDual PTP1B/DPP4 inhibitory potential of Agathosma betulina, Cymbopogon citratus and Artemisia afra: structure-based modeling of phytochemical leads and essential oil bioassays — in vitro/in silico studyView study →}.

Gap: no human glucose data. The rat dose corresponded to a person drinking about 250 mL of the extract a day ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

The essential oils of both buchu species inhibited 5-lipoxygenase in vitro, with IC₅₀ values around 50–60 µg/mL, a weak effect ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

An ethanolic leaf extract at 250 µg/mL inhibited COX-1 by 98% and COX-2 by 25% ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

In human blood cells, the commercial aqueous extract reduced the respiratory burst of neutrophils and monocytes and lowered the release of IL-6 and TNF-α. The composition of the fractions tested was not reported, and the work has not been repeated by another group ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

The leaf also contains the flavonoids diosmin, hesperidin and rutin, each studied on its own for anti-inflammatory and vascular effects ^{2Reference 2Moolla A · 2008ReviewMoolla A, Viljoen AM. (2008). ‘Buchu’ — Agathosma betulina and Agathosma crenulata (Rutaceae): a review. J Ethnopharmacol. https://pubmed.ncbi.nlm.nih.gov/18725278/View study →}.

Gap: all of it is in vitro; there is no animal or human inflammation study.

In the one direct test of the oils, neither A. betulina nor A. crenulata oil was active against Enterococcus hirae or Pseudomonas aeruginosa, and both had very low activity against Escherichia coli, Saccharomyces cerevisiae and Staphylococcus aureus ^{1Reference 1Lis-Balchin M et al. · 2001In vitroBuchu (Agathosma betulina and A. crenulata, Rutaceae) essential oils: their pharmacological action on guinea-pig ileum and antimicrobial activity on microorganisms — in vitro studyView study →}.

A later set of tests found the oils weak (MIC 3–32 mg/mL), while methanol–dichloromethane leaf extracts were moderately active (MIC 2–6 mg/mL) against a range of bacteria and Candida albicans ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}. The extract also prevented biofilm formation in vitro ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

A mixture of A. crenulata with Dodonaea viscosa and Eucalyptus globulus was more active than its single herbs ^{7Reference 7Zonyane S et al. · 2013In vitroAntimicrobial interactions of Khoi-San poly-herbal remedies with emphasis on the combination Agathosma crenulata, Dodonaea viscosa and Eucalyptus globulus — in vitro studyView study →}.

Gap: the active concentrations are far higher than standard antibiotics, and the solvent extracts differ from a tea or tincture ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}. No one has tested activity at concentrations reached in urine.

In the mouse formalin test, an ethanolic buchu extract at 200 mg/kg reduced paw-licking by 55% in the early phase and 45% in the later, inflammatory phase ^{3,6Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →Reference 6Chiguvare H et al. · 2016In vitroSynthesis of silver nanoparticles using buchu plant extracts and their analgesic properties — in vitro/in vivo studyView study →}. Silver nanoparticles made with the extract were more effective than both the extract and aspirin ^{6Reference 6Chiguvare H et al. · 2016In vitroSynthesis of silver nanoparticles using buchu plant extracts and their analgesic properties — in vitro/in vivo studyView study →}.

Gap: one mouse study, at a single dose, with no human data.

Pulegone. Buchu’s essential oil contains pulegone, the monoterpene ketone behind the toxicity of pennyroyal oil. The liver converts it, mainly through CYP450 enzymes, to menthofuran and other reactive metabolites that deplete glutathione and can cause liver injury at high doses ^{8,9,10,17Reference 8Zárybnický T et al. · 2018ReviewHepatotoxicity of monoterpenes and sesquiterpenes — reviewView study →Reference 9Gordon P · 2015ReviewA decades-long investigation of acute metabolism-based hepatotoxicity by herbal constituents: a case study of pennyroyal oil — reviewView study →Reference 10Zárybnický T et al. · 2018In vitroInter-individual variability in acute toxicity of R-pulegone and R-menthofuran in human liver slices — in vitro studyView study →Reference 17Khojasteh-Bakht SC et al. · 1999In vitroMetabolism of (R)-(+)-pulegone and (R)-(+)-menthofuran by human liver cytochrome P-450s: evidence for formation of a furan epoxide — in vitro studyView study →}. High doses of buchu oil were hepatotoxic in rats and affected liver and uterine function ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

Species. Pulegone makes up a few percent of A. betulina oil (2.4–4.5% in one study) but 31–73% of A. crenulata oil, so oil from A. crenulata calls for more caution ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

Leaf infusion. Pulegone is not water-soluble, so this caution does not apply in the same way to water extracts ^{3Reference 3Brendler T · 2022ReviewBuchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized? — reviewView study →}.

Flavouring use. Buchu leaf oil and buchu leaf extract hold FEMA GRAS status as flavouring ingredients ^{11Reference 11Cohen SM et al. · 2020ReviewFEMA GRAS assessment of natural flavor complexes: mint, buchu, dill and caraway derived flavoring ingredients — reviewView study →}. EFSA judged the oil safe as a feed flavouring at set levels, and classed it as a skin and eye irritant and a skin and respiratory sensitiser for people handling it ^{12Reference 12Bampidis V et al. · 2022ReviewSafety and efficacy of a feed additive consisting of an essential oil from the leaves of Agathosma betulina/A. crenulata — reviewView study →}.

Interactions. In tests with human liver enzymes, pulegone is converted to menthofuran mainly by CYP2E1, CYP1A2 and CYP2C19 ^{17Reference 17Khojasteh-Bakht SC et al. · 1999In vitroMetabolism of (R)-(+)-pulegone and (R)-(+)-menthofuran by human liver cytochrome P-450s: evidence for formation of a furan epoxide — in vitro studyView study →}. No human or animal drug-interaction study of buchu itself has been done, so the shared enzymes are a theoretical reason for caution with the oil.