Mesembrine: What It Is, What Lab Studies Found, and What Labels Leave Out
Mesembrine gets the most attention of kanna's alkaloids, but it is one of 25, and the best-studied extract is low in it.
Mesembrine is the name you will see most often when kanna's chemistry comes up, and the one brands most like to put on a label. It is a real and interesting compound with a lab research record. It is also easily over-read. This post explains what mesembrine is, what the pharmacology studies found, how it differs from its relatives, and why a mesembrine number on a label needs context.
Mesembrine is the best-known of 25 alkaloids identified in kanna (Sceletium tortuosum) [1]. In lab work it bound the serotonin transporter more strongly than the other alkaloids tested [2]. It has not been tested alone in people, and the extract used in most human trials is low in it [5]. Mesembrine is not an approved medicine or an SSRI.
What is mesembrine?
It is an alkaloid found in kanna and the namesake of the plant's main alkaloid class.
A 2021 review counted 25 alkaloids in four structural classes in Sceletium tortuosum (mesembrine, Sceletium A4, joubertiamine and tortuosamine), with the mesembrine class predominant [1]. The plant is endemic to South Africa and has a long history of being chewed, smoked, drunk as tea or snuffed [1][9]. Other members of the mesembrine class include mesembrenone, mesembrenol and mesembranol [4]. For the plant overall, see what is kanna.
How much mesembrine a given plant contains varies. Chemical profiling has found population-specific differences between sites, with the highest mesembrine in samples from two of the locations studied [7]. In a hydroponics experiment, growing medium affected alkaloid levels, and shoots held more mesembrine than roots [8].
What did lab studies find about mesembrine?
It bound the serotonin transporter tightly in a binding assay, and a later cell study complicated the explanation.
In a 2011 pharmacology study, a standardized Sceletium extract blocked the serotonin transporter (IC50 4.3 ug/ml) and inhibited the enzyme PDE4 (IC50 8.5 ug/ml). Of the purified alkaloids tested, mesembrine was the most active at the transporter, with a Ki of 1.4 nM [2]. The authors suggested this activity may explain the traditional use. A 2016 study in human astrocytes and mouse hippocampal cells used a high-mesembrine extract and argued that serotonin reuptake inhibition may be secondary to a monoamine-releasing effect; the extract also showed only mild inhibition of acetylcholinesterase and MAO-A [3]. That is one lab group's reading of cell data, and the mechanism is still unsettled. Our how does kanna work post sets out the competing explanations.
In a 2024 zebrafish-larvae study, only mesembrine, among four alkaloids tested at the concentrations in the extract, significantly contributed to the anxiety-like behavior outcome. No single alkaloid explained the antidepressant-like outcome, which the authors suggest may need several constituents acting together [4]. Fish larvae are far from humans, and the study is a pointer for further research, not evidence of an effect in people.
Is mesembrine an SSRI?
No. It shows overlapping activity at the serotonin transporter in the lab, but it is not a drug and has not been tested as one.
SSRIs are prescription medicines tested and approved for specific conditions. Kanna is a supplement ingredient that the FDA has not reviewed for safety and effectiveness [10]. The practical consequence of the overlap is caution: WebMD lists SSRIs, SNRIs, MAOIs, tricyclic antidepressants, antipsychotics, triptans and St. John's wort as possible interaction concerns [10]. If you take any of these, ask a doctor or pharmacist before trying kanna. See kanna and SSRIs and is kanna safe.
How is mesembrine different from mesembrenone?
They are sibling alkaloids with different lab profiles.
| Mesembrine | Mesembrenone | |
|---|---|---|
| Serotonin transporter (2011 lab study) | Most active alkaloid tested (Ki 1.4 nM) [2] | Active (IC50 below 1 uM) [2] |
| PDE4 (2011 lab study) | Abstract names mesembrenone, not mesembrine, as active [2] | Active (IC50 below 1 uM) [2] |
| Zebrafish anxiety-like outcome | Only alkaloid tested with a significant effect [4] | Not significant alone [4] |
| Share of Zembrin alkaloids | Under 20% [5] | With mesembrenol, at least 60% [5] |
| Change on fermentation | Fell from 1.33% to 0.05% in one experiment [6] | Delta-7 form rose from below quantitation to 0.11% [6] |
Different alkaloids may contribute different things, and no study has isolated their effects in people.
Why is Zembrin low in mesembrine?
Because it was specified that way: mostly mesembrenone and mesembrenol, with mesembrine as a smaller share.
The Zembrin extract is described as standardized to 0.35 to 0.45% total alkaloids, with mesembrenone and mesembrenol at least 60% and mesembrine under 20% [5]. The human kanna trials we reviewed all used this extract, at 8 or 25 mg. That means the human evidence does not come from a mesembrine-rich product, and "high mesembrine" extracts are a different thing with their own, mostly cell-based, research [3]. See Zembrin explained, including who authored and funded the trials.
Is mesembrine stable?
It changed in water and light under lab conditions, which makes drinks an open question.
Researchers at Rhodes University exposed pure mesembrine hydrochloride to different conditions. In aqueous solutions it transformed in sunlight, and the transformation was absent in the dark and in methanol [6]. In the fermentation experiment on plant material, mesembrine content dropped sharply [6]. Those are experiments on a pure compound and on fermented plant, not on finished beverages. We found no published study of mesembrine stability in a ready-to-drink product, so we cannot say how a given can behaves over its shelf life. If a brand quotes a mesembrine figure for a liquid, the fair questions are when and how it was measured.
Has mesembrine been studied in people?
Not on its own, as far as we could find.
The human trials of kanna we reviewed used a whole extract, not purified mesembrine. They were small studies in healthy adults, and several involved authors tied to the extract's developer (see Zembrin explained). A 2021 review noted that the plant has not yet been studied in a clinical population [1]. So statements such as "mesembrine does X in people" go beyond the published evidence. What exists is lab binding data, cell studies and a zebrafish experiment. For the human results as measured, see what the research shows.
What does mesembrine content on a label tell you?
Only something specific: the amount of that one alkaloid in the tested material, by a stated method.
It does not say how the extract behaves overall, because other alkaloids differ in activity, and the best-studied extract is low in mesembrine [2][5]. It also does not transfer between products. Wild plants vary [7][9], processing shifts the profile [6], and US labels are not required to list alkaloid content at all. A mesembrine or total-alkaloid number is most useful when it comes with the extract's name, the method and a lot-matched lab report. Our guide to reading a kanna label shows what to check, and kanna dosage explains why milligrams aren't comparable.
An overall caution from the literature: a 2026 review of Zembrin and related studies found favorable safety and potential efficacy but mixed evidence, small samples and unrepresentative populations [11]. Mesembrine is an interesting molecule. It is not proof of anything about any particular product.
This page is general information, not medical advice. These statements have not been evaluated by the FDA. Kanna products are not intended for any disease or health condition. kannadrinks.com is published by Psilly Goose, a kanna drink maker.
References
- Olatunji TL, et al. Sceletium tortuosum: a review on its phytochemistry, pharmacokinetics, biological and clinical activities. J Ethnopharmacol 2021;280:114476. PubMed
- Harvey AL, et al. Pharmacological actions of the South African medicinal and functional food plant Sceletium tortuosum and its principal alkaloids. J Ethnopharmacol 2011;137(3):1124-9. PubMed
- Coetzee DD, et al. High-mesembrine Sceletium extract (Trimesemine) is a monoamine releasing agent, rather than only a selective serotonin reuptake inhibitor. J Ethnopharmacol 2016;177:111-6. PubMed
- Gericke J, et al. Sceletium tortuosum-derived mesembrine significantly contributes to the anxiolytic effect of Zembrin, but its anti-depressant effect may require synergy of multiple plant constituents. J Ethnopharmacol 2024;319:117113. PubMed
- Murbach TS, et al. A toxicological safety assessment of a standardized extract of Sceletium tortuosum (Zembrin) in rats. Food Chem Toxicol 2014;74:190-9. PubMed
- Patnala S, Kanfer I. Investigations of the phytochemical content of Sceletium tortuosum following the preparation of "Kougoed" by fermentation of plant material. J Ethnopharmacol 2009;121:86-91. PubMed
- Reddy K, et al. Mass spectrometry metabolomics and feature-based molecular networking reveals population-specific chemistry in some species of the Sceletium genus. Front Nutr 2022;9:819753. PMC
- Faber RJ, et al. Variabilities in alkaloid concentration of Sceletium tortuosum (L.) N.E. Br in response to different soilless growing media and fertigation regimes in hydroponics. Heliyon 2020;6(11):e05479. PMC
- Manganyi MC, et al. A chewable cure "Kanna": biological and pharmaceutical properties of Sceletium tortuosum. Molecules 2021;26(9):2557. PMC
- WebMD. Sceletium: Uses, side effects, interactions. webmd.com
- de Jong M, et al. Mesembryanthemum tortuosum and Zembrin: mixed evidence from in vivo animal and clinical studies on their antidepressant and anxiolytic effects. Planta Med 2026;92(8):806-823. PubMed
Frequently asked questions
What is mesembrine?
Mesembrine is the best-known alkaloid in kanna (Sceletium tortuosum). It belongs to the mesembrine class, the predominant of four structural classes among the 25 alkaloids identified in the plant [1].
Does mesembrine affect serotonin?
In a 2011 lab study, mesembrine was the most active of three tested alkaloids at the serotonin transporter (Ki 1.4 nM) [2]. A 2016 cell study argued that serotonin reuptake inhibition may be secondary to a monoamine-releasing action [3]. These are lab findings, not proof of effects in people.
Is kanna an SSRI?
No. SSRIs are approved prescription medicines, while kanna is an unapproved supplement ingredient. Lab work found overlapping activity at the serotonin transporter [2], which is why WebMD flags possible interactions with SSRIs and other serotonergic drugs [10]. Ask a doctor before combining them.
What is the difference between mesembrine and mesembrenone?
They are different alkaloids in the same family. In the 2011 study, mesembrine was the most active at the serotonin transporter, while mesembrenone was active against both the transporter and PDE4 [2].
Is mesembrine stable?
Not necessarily. In lab experiments, pure mesembrine hydrochloride changed into another alkaloid in water exposed to sunlight, but not in the dark or in methanol [6]. We found no stability study in finished drinks.