Boldo (Peumus boldus) is a plant that has been predominantly used in South America, but it has managed to spread to other continents as well. As common with herbs stemming from Latin America, the term boldo is often associated with other herbs such as Plectranthus barbatus, P. neochilus, P. amboinicus and Vernonia condensate. 1

Boldo is used in traditional medicine for treatment of rheumatism, syphilis, anxiety, gonorrhea, trouble sleeping, cysts, stomach pain, ear pain, urinary tract infections, diabetes, disorders of gastrointestinal tract, cancer and liver disorders.

Peumus boldus (boldo), macho

Taste: similar to lemongrass, not bitter

Constituents: alkaloids (0.06-2.8%, mostly coclaurine, laudanosine, laudanosoline, boldine, isoboldine, isocorydine, norisocorydine, isocorydine N-oxide, N-methyllaurotetanine, laurotetanine, laurolitsine), flavonoids (catechin, peumoside, boldoside, fragroside), tannins (1.2%), resins, coumarins (0.5%), essential oil (2-4%, mostly ascaridole, camphene, linalool, limonene, boldine, dehydroboldine, isoboldine, isocorydine, laurotetanin, p-cymene, eucalyptol) 1

Toxicity

Toxicity of boldo stems from several of its alkaloids and ascaridole, a constituent of its essential oil. Ascaridole content may reach even above 50% of the essential oil, making it very dangerous for tinctures and cold infusions.

Ascaridole is carcinogenic and highly toxic, even more so when it’s dissolved in ethanol.

Ascaridole may cause vomiting, diarrhea, convulsions, depression of CNS, delirium, jaundice, pulmonary edema, albuminuria, hematuria, coma and death. 1

Boldine and sparteine were shown to have teratogenic and abortifacient effects in rats. 1 Hydroethanolic extract may also increase levels of AST, ALT, cholesterol, and decrease urea, bilirubin and glucose. 2

LD50 of essential oil of boldo was determined to be 130 mg/kg, making it one of the most toxic essential oils out there. 3

Other side effects that have been reported upon are irritation of kidneys and urinary tract, paralysis, allergic reactions, myocardial difficulties, liver damage and skin irritation.

Potential benefits

Boldo was found to be chemoprotective (due to presence of boldine and catechin), protecting liver from oxidative damage induced by cisplatin and inhibiting lipid peroxidation. 4

Another study found that aqueous extract of boldo was more effective at protecting against manganese-induced neurotoxicity than its compound boldine. 5

Potential benefits are most likely due to the presence of boldine in essential oil.

Boldine is said to stimulate intestinal juices and bile flow. Boldine is also an antioxidant, combat lipid peroxidation, hepatoprotective, anti-inflammatory, antipyretic, cytoprotective

Secoboldine and boldine inhibit platelet aggregation.

Ascaridole is active against intestinal worms.

Essential oil is active against Eschericheria coli, Neisseria gonorrhoeae, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, Bacillus cereus, Fusarium oxysporum, Rhizopus nigricans, Aspergillus niger, Trichophyton mentagrophytes, Trypanosoma cruzi and Leishmania amazonensis. 1

Boldo’s potential anticancer benefits may be attributed to boldine which acts as a telomerase inhibitor. 6

Final verdict: This herb is absolutely not worth the risks. Even if you manage to find boldo leaf that contains very little ascaridole, you will not be able to avoid alkaloids that it contains. There’s a reason why the dosage of boldo leaf is so small. It’s not recommended to use boldo for more than 4 weeks.

References

1. Mariano, X. M., de Souza, W. F. M., Rocha, C. B. & Moreira, R. F. A. Bioactive volatile fraction of Chilean boldo ( Peumus boldus Molina) – an overview. J. Essent. Oil Res. 31, 474–486 (2019).

2. Almeida, E. R. de, Melo, A. M. & Xavier, H. Toxicological evaluation of the hydro-alcohol extract of the dry leaves of Peumus boldus and boldine in rats. Phyther. Res. 14, 99–102 (2000).

3. Tisserand, R. & Young, R. Essential Oil Safety: A Guide for Health Care Professionals: Second Edition. (Churchill Livingstone, 2013). doi:10.1016/C2009-0-52351-3

4. Fernández, J., Lagos, P., Rivera, P. & Zamorano-Ponce, E. Effect of boldo ( Peumus boldus Molina) infusion on lipoperoxidation induced by cisplatin in mice liver. Phyther. Res. 23, 1024–1027 (2009).

5. Bianchini, M. C. et al. Peumus boldus (Boldo) Aqueous Extract Present Better Protective Effect than Boldine Against Manganese-Induced Toxicity in D. melanogaster. Neurochem. Res. 41, 2699–2707 (2016).

6. Kazemi Noureini, S. & Tanavar, F. Boldine, a natural aporphine alkaloid, inhibits telomerase at non-toxic concentrations. Chem. Biol. Interact. 231, 27–34 (2015).