Butterfly Bush (Petalostylis) (Petalostylis cassioides)

What Is Butterfly Bush?

Butterfly bush (Petalostylis cassioides) is a shrub of the pea family from arid inland Australia, with finely divided leaves and orange-yellow flowers ^{8,10Reference 8Ross JH · 1998Petalostylis cassioidesView study →Reference 10Ross JH · 1998Petalostylis (genus)View study →}. Aboriginal people rubbed its crushed leaves on the skin to treat various ailments ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}.

It grows on sand plains, stony ground and rocky outcrops and along creek beds across much of arid Western Australia and the Northern Territory ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}.

Its leaves and stems contain a small fraction of tryptamine alkaloids, including N,N-dimethyltryptamine (DMT) and the β-carboline tetrahydroharman ^{1Reference 1Johns SR et al. · 1966Alkaloids of the Australian LeguminosaeView study →}. The plant itself has not been studied for any effect.

The name “butterfly bush” more often means the unrelated garden shrub Buddleja. It is also shared by this plant’s only relative, Petalostylis labicheoides ^{9Reference 9Ross JH · 1998Petalostylis labicheoidesView study →}.

How Is Butterfly Bush Used?

The one recorded use is Aboriginal: the leaves were crushed and rubbed on the skin to treat various ailments ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}. There is no recorded internal use, no pharmacopoeial monograph and no commercial product.

Traditional Uses

Australian Aboriginal Medicine

Aboriginal people rubbed the crushed leaves on their skin to treat various ailments ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}.

Botany

Butterfly bush is a shrub in the pea family (Fabaceae) that grows up to 3 m tall, sometimes with sprawling stems ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}. Its branchlets range from hairless to densely covered in spreading white hairs, and are sometimes coated with a waxy bloom ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}.

Petalostylis is a genus of two species, both endemic to Australia and largely confined to its arid areas ^{10Reference 10Ross JH · 1998Petalostylis (genus)View study →}. The name refers to the petal-like style of the flower ^{10Reference 10Ross JH · 1998Petalostylis (genus)View study →}.

The leaves are pinnate, with a stiff central stalk 1.5–14 cm long that can persist after the leaflets fall ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}. They carry mostly 11–80 small leaflets, usually obovate to heart-shaped and 2–18 mm long, often notched at the tip ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}.

The flowers have five orange-yellow petals 1.5–2.2 cm long ^{8,10Reference 8Ross JH · 1998Petalostylis cassioidesView study →Reference 10Ross JH · 1998Petalostylis (genus)View study →}. The uppermost petal usually carries a red flare at its base ^{10Reference 10Ross JH · 1998Petalostylis (genus)View study →}. The pod is 2.3–3 cm long ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}.

The species is variable, and its extreme forms look very different from one another ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}. Several names have been placed in synonymy under it, and it has also been treated as a variety of P. labicheoides (P. labicheoides var. cassioides), the name used in the 1966 chemistry paper ^{1,8Reference 1Johns SR et al. · 1966Alkaloids of the Australian LeguminosaeView study →Reference 8Ross JH · 1998Petalostylis cassioidesView study →}.

Its relative P. labicheoides is also a shrub up to 3 m tall, but it carries fewer, larger leaflets: 3–19 per leaf, each 0.8–3 cm long, on a shorter stalk ^{9Reference 9Ross JH · 1998Petalostylis labicheoidesView study →}.

Distribution

Butterfly bush grows throughout much of arid Western Australia and the Northern Territory, and in north-western South Australia and north-western Queensland ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}.

It grows on sand plains, stony plains, sandstone and rocky outcrops, scree slopes and gravel, and along creek beds ^{8Reference 8Ross JH · 1998Petalostylis cassioidesView study →}.

Its relative P. labicheoides has a separate range, in north-western Western Australia, the Flinders Ranges, central and eastern Queensland and New South Wales ^{9Reference 9Ross JH · 1998Petalostylis labicheoidesView study →}. The two ranges overlap little ^{9Reference 9Ross JH · 1998Petalostylis labicheoidesView study →}.

Growing Conditions

Cultivation snapshot for Butterfly Bush (Petalostylis)

Lifeperennial shrubZoneUSDA 9-11Sunfull sunWaterarid-adapted; needs sharp drainageHabitto 3 m, sometimes sprawling

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Phytochemistry

A 1966 study of leaves and stems, published under the name Petalostylis labicheoides var. cassioides, reported a group of tryptamine-type indole alkaloids ^{1Reference 1Johns SR et al. · 1966Alkaloids of the Australian LeguminosaeView study →}. They were N,N-dimethyltryptamine, N-methyltryptamine, tryptamine and the β-carboline tetrahydroharman ^{1Reference 1Johns SR et al. · 1966Alkaloids of the Australian LeguminosaeView study →}.

Together they made up roughly 0.4–0.5% of the dried aerial material ^{1Reference 1Johns SR et al. · 1966Alkaloids of the Australian LeguminosaeView study →}. The study gave no figures for the individual compounds.

Constituent Summary

Tryptamine alkaloids from leaf and stem; about 0.4–0.5% of dry weight in total ^{1Reference 1Johns SR et al. · 1966Alkaloids of the Australian LeguminosaeView study →}.

Grouped by class · 4 compounds

Indole Alkaloids4 compoundsno data

Indole AlkaloidsN,N-DimethyltryptamineNo data

Indole AlkaloidsN-MethyltryptamineNo data

Indole AlkaloidsTryptamineNo data

Indole AlkaloidsTetrahydroharmanNo data

Pharmacology & Research

No study has tested Petalostylis cassioides or its extracts for any effect. The published work on the genus covers its alkaloids, its evolutionary relationships and its population genetics ^{1,6,7Reference 1Johns SR et al. · 1966Alkaloids of the Australian LeguminosaeView study →Reference 6Bai HR et al. · 2021Plastid phylogenomic insights into the evolution of subfamily Dialioideae (Leguminosae)View study →Reference 7Bradbury D et al. · 2022The nuanced nature of mesic refugia in arid landscapes: a tale of two peasView study →}.

What is known about its pharmacology comes from its constituents. DMT is a short-acting psychedelic that acts at the serotonin 5-HT2A receptor ^{2Reference 2Bhat A et al. · 2026Short- and Long-Acting Psychedelics: Structure–Activity Relationships, Pharmacology, and Implications for Neuropsychiatric TherapeuticsView study →}. Aromatic β-carbolines such as harman and harmine inhibit the enzyme monoamine oxidase A (MAO-A) ^{3,4Reference 3Herraiz T · 2023Herraiz T. β-Carboline Alkaloids in Soy Sauce and Inhibition of Monoamine Oxidase (MAO). Molecules. 2023;28(6):2723. https://doi.org/10.3390/molecules28062723View study →Reference 4Ribeiro GSG et al. · 2026Predicting Drug–Drug Interactions Between Ayahuasca Alkaloids and SSRIs Using Physiologically Based Pharmacokinetic ModelingView study →}, which is what makes DMT active by mouth in ayahuasca ^{4,5Reference 4Ribeiro GSG et al. · 2026Predicting Drug–Drug Interactions Between Ayahuasca Alkaloids and SSRIs Using Physiologically Based Pharmacokinetic ModelingView study →Reference 5Wittayakarn N et al. · 2025AnimalDevelopment of a Physiologically Based Pharmacokinetic Model of N,N-Dimethyltryptamine, Harmine, and Their Interactions from Ayahuasca in Rats and HumansView study →}.

What the Evidence Supports

Best-supported: no effect of the plant has been tested.
Emerging, worth watching: purified DMT and ayahuasca are being studied for depression and substance-use disorders ^{2Reference 2Bhat A et al. · 2026Short- and Long-Acting Psychedelics: Structure–Activity Relationships, Pharmacology, and Implications for Neuropsychiatric TherapeuticsView study →}.
Mechanistically thin: everything known comes from the isolated alkaloids ^{1,2,3Reference 1Johns SR et al. · 1966Alkaloids of the Australian LeguminosaeView study →Reference 2Bhat A et al. · 2026Short- and Long-Acting Psychedelics: Structure–Activity Relationships, Pharmacology, and Implications for Neuropsychiatric TherapeuticsView study →Reference 3Herraiz T · 2023Herraiz T. β-Carboline Alkaloids in Soy Sauce and Inhibition of Monoamine Oxidase (MAO). Molecules. 2023;28(6):2723. https://doi.org/10.3390/molecules28062723View study →}.

The pharmacology belongs to the isolated alkaloids. Studies of purified DMT and of ayahuasca brews do not describe this shrub.

Evidence by IndicationStrength of support

0. Evidence by Indication

Mechanisms

DMT is a tryptamine that acts at the serotonin 5-HT2A receptor ^{2Reference 2Bhat A et al. · 2026Short- and Long-Acting Psychedelics: Structure–Activity Relationships, Pharmacology, and Implications for Neuropsychiatric TherapeuticsView study →}. Taken by mouth on its own it is broken down by MAO-A, which is why ayahuasca pairs it with an MAO-A-inhibiting β-carboline ^{4,5Reference 4Ribeiro GSG et al. · 2026Predicting Drug–Drug Interactions Between Ayahuasca Alkaloids and SSRIs Using Physiologically Based Pharmacokinetic ModelingView study →Reference 5Wittayakarn N et al. · 2025AnimalDevelopment of a Physiologically Based Pharmacokinetic Model of N,N-Dimethyltryptamine, Harmine, and Their Interactions from Ayahuasca in Rats and HumansView study →}.

Tetrahydroharman belongs to the β-carboline class. MAO-A inhibition has been measured for aromatic β-carbolines such as harman ^{3Reference 3Herraiz T · 2023Herraiz T. β-Carboline Alkaloids in Soy Sauce and Inhibition of Monoamine Oxidase (MAO). Molecules. 2023;28(6):2723. https://doi.org/10.3390/molecules28062723View study →}, not for this plant.

Mechanism	Drives	Key compounds
5-HT2A receptor agonism (serotonergic psychedelic)	psychoactivity; basis of isolated-DMT and ayahuasca research	N,N-dimethyltryptamine
MAO-A inhibition (β-carboline class)	slows breakdown of DMT and other amines; drug-interaction risk	tetrahydroharman

Clinical Trials

No registered clinical trials of Petalostylis cassioides or its extracts were identified. Trials of isolated DMT and of ayahuasca exist, but they use purified molecules and defined brews.

Completed	Planned	Terminated	Preclinical
0	0	0	0

Last checked: July 2026.

Dosage

No dose has been established. The plant has no recorded internal use, no pharmacopoeial monograph and no toxicology data.

Safety & Pregnancy

Do not take it internally. The leaves and stems carry DMT, a serotonergic psychedelic, together with a β-carboline, and their amounts vary ^{1Reference 1Johns SR et al. · 1966Alkaloids of the Australian LeguminosaeView study →}.

Safety at a Glance

Moderate toxicity

Do not ingest. No toxicology, dosing or human-use data exist for the plant.
DMT with a β-carboline. The same pairing makes oral ayahuasca active ^{4,5Reference 4Ribeiro GSG et al. · 2026Predicting Drug–Drug Interactions Between Ayahuasca Alkaloids and SSRIs Using Physiologically Based Pharmacokinetic ModelingView study →Reference 5Wittayakarn N et al. · 2025AnimalDevelopment of a Physiologically Based Pharmacokinetic Model of N,N-Dimethyltryptamine, Harmine, and Their Interactions from Ayahuasca in Rats and HumansView study →}.
Drug interactions. Serotonergic drugs, SSRIs and tyramine-rich foods are the concern with MAO-A inhibition, and SSRIs change exposure to ayahuasca alkaloids ^{4Reference 4Ribeiro GSG et al. · 2026Predicting Drug–Drug Interactions Between Ayahuasca Alkaloids and SSRIs Using Physiologically Based Pharmacokinetic ModelingView study →}.
Avoid in pregnancy and breastfeeding.
Legal status. DMT is a controlled psychedelic in most jurisdictions.

Full Safety & Interactions Detail

Alkaloids. Leaf and stem carry about 0.4–0.5% tryptamine alkaloids, including DMT and the β-carboline tetrahydroharman ^{1Reference 1Johns SR et al. · 1966Alkaloids of the Australian LeguminosaeView study →}. Their content is expected to vary with plant part, provenance and season.

DMT. DMT acts at the 5-HT2A receptor and is a controlled psychedelic in most jurisdictions ^{2Reference 2Bhat A et al. · 2026Short- and Long-Acting Psychedelics: Structure–Activity Relationships, Pharmacology, and Implications for Neuropsychiatric TherapeuticsView study →}.

β-carbolines and interactions. Aromatic β-carbolines inhibit MAO-A ^{3Reference 3Herraiz T · 2023Herraiz T. β-Carboline Alkaloids in Soy Sauce and Inhibition of Monoamine Oxidase (MAO). Molecules. 2023;28(6):2723. https://doi.org/10.3390/molecules28062723View study →}. In ayahuasca, the β-carboline harmine lets DMT survive to reach the brain ^{5Reference 5Wittayakarn N et al. · 2025AnimalDevelopment of a Physiologically Based Pharmacokinetic Model of N,N-Dimethyltryptamine, Harmine, and Their Interactions from Ayahuasca in Rats and HumansView study →}. Modelling predicts that the SSRIs fluoxetine and paroxetine raise exposure to both DMT and harmine ^{4Reference 4Ribeiro GSG et al. · 2026Predicting Drug–Drug Interactions Between Ayahuasca Alkaloids and SSRIs Using Physiologically Based Pharmacokinetic ModelingView study →}. Serotonergic drugs and tyramine-rich foods are the other interactions of concern with MAO-A inhibition.

What is not known. No interaction or pregnancy study exists for the plant itself. These cautions come from its chemistry and from ayahuasca pharmacology.

Pregnancy & Lactation

Avoid in pregnancy Avoid while breastfeeding

Avoid. No study has examined Petalostylis cassioides in pregnancy or breastfeeding. The plant contains a serotonergic psychedelic (DMT) and a β-carboline alkaloid ^{1Reference 1Johns SR et al. · 1966Alkaloids of the Australian LeguminosaeView study →}, and neither has an established safe use in pregnancy.

References

Johns SR, Lamberton JA, Sioumis AA. Alkaloids of the Australian Leguminosae. VI. Alkaloids of Petalostylis labicheoides var. casseoides Benth. Australian Journal of Chemistry. 1966;19:893. https://doi.org/10.1071/CH9660893
Bhat A, Zolali E, Sakib MA, et al. Short- and Long-Acting Psychedelics: Structure–Activity Relationships, Pharmacology, and Implications for Neuropsychiatric Therapeutics. ACS Chemical Neuroscience. 2026;17(12):2278–2301. https://doi.org/10.1021/acschemneuro.6c00202
Herraiz T. β-Carboline Alkaloids in Soy Sauce and Inhibition of Monoamine Oxidase (MAO). Molecules. 2023;28(6):2723. https://doi.org/10.3390/molecules28062723
Ribeiro GSG, et al. Predicting Drug–Drug Interactions Between Ayahuasca Alkaloids and SSRIs Using Physiologically Based Pharmacokinetic Modeling. Frontiers in Molecular Biosciences. 2026. https://doi.org/10.3389/fmolb.2026.1768402
Wittayakarn N, et al. Development of a Physiologically Based Pharmacokinetic Model of N,N-Dimethyltryptamine, Harmine, and Their Interactions from Ayahuasca in Rats and Humans. Toxicological Sciences. 2025;208(1):48. https://doi.org/10.1093/toxsci/kfaf118
Bai HR, Oyebanji O, Zhang R, Yi TS. Plastid phylogenomic insights into the evolution of subfamily Dialioideae (Leguminosae). Plant Diversity. 2021;43(1):27–34. https://doi.org/10.1016/j.pld.2020.06.008
Bradbury D, et al. The nuanced nature of mesic refugia in arid landscapes: a tale of two peas. Annals of Botany. 2022;130(6):901. https://doi.org/10.1093/aob/mcac126
Ross JH. (1998). Petalostylis cassioides. In: Flora of Australia, Vol. 12. Australian Biological Resources Study, Canberra. https://profiles.ala.org.au/opus/foa/profile/Petalostylis%20cassioides
Ross JH. (1998). Petalostylis labicheoides. In: Flora of Australia, Vol. 12. Australian Biological Resources Study, Canberra. https://profiles.ala.org.au/opus/foa/profile/Petalostylis%20labicheoides
Ross JH. (1998). Petalostylis (genus). In: Flora of Australia, Vol. 12. Australian Biological Resources Study, Canberra. https://profiles.ala.org.au/opus/foa/profile/Petalostylis