Crape Jasmine: Alkaloid Pharmacology and the Real Toxicity Profile

Every claim on the other three pages of this Benefits leg traces back to the same underlying fact: crape jasmine is a genuinely prolific alkaloid factory, and its chemistry is close enough to some dangerous relatives that vague family-level fear and precise, checkable caution can look similar from a distance but are not the same thing. This page does the precise version — naming which alkaloids are actually confirmed in this species rather than borrowed from a related one, showing what those alkaloids do in isolation, and tracing exactly how many chemical steps separate this ornamental garden shrub from a compound with a documented history of killing people.

Table of Contents

1. What Is Actually Being Claimed
2. Sixty-Six Named Alkaloids: The Chemical Scope
3. Which Alkaloids Are Actually Documented Here
4. Conophylline: A Case Study in Species Precision
5. Cytotoxicity to Cancer Cell Lines: Real Potency, Ambiguous Meaning
6. The Hepatoprotective Counter-Finding
7. A Toxicity Screening Number, and Why It Stops There
8. Voacangine, Ibogaine, and the Documented Cardiac Risk
9. Why a Marker Compound Cannot Confirm What Is in a Bottle
10. What This Plant Is Not Documented to Do
11. Evidence Ledger for This Page
12. Practical Guidance
13. Key Research Papers
14. Connections

What Is Actually Being Claimed

Two claims run through the marketing and popular writing about this plant’s chemistry, and they pull in opposite directions unless handled precisely. The first is a benefit claim: crape jasmine’s alkaloids show real cytotoxic, antidiabetic and enzyme-inhibiting activity in the laboratory, which is offered as evidence of medicinal potential. The second is a hazard claim: some of those same alkaloids are chemically close to ibogaine, a compound with documented fatal cardiac risk. Both claims are true. The point of this page is that they are largely true for the same reason — this plant makes potent, biologically active small molecules, and potency is not a one-directional property. A compound active enough to be pharmacologically interesting is, by the same token, a compound whose uncontrolled dose is a real question rather than a rhetorical one.

Sixty-Six Named Alkaloids: The Chemical Scope

The standard reference review of this plant’s chemistry — a 2008 paper in the Indian Journal of Medical Research by a Chiang Mai University group — catalogued sixty-six distinct alkaloids isolated and structurally identified specifically from Tabernaemontana divaricata, alongside non-alkaloid constituents including enzymes, pyrolytic oil, hydrocarbons, terpenoids and phenolic acids. That is a precise, citable number for this species specifically, not a vague genus-wide estimate, and it is worth holding onto: this is not a plant with one or two interesting compounds surrounded by inert filler. It is a plant whose chemistry has been mapped in real structural detail, part of why it keeps attracting phytochemistry groups looking for new isolable compounds — several of the papers cited below, published across 2019 to 2024, describe alkaloids newly identified from this species, meaning the sixty-six figure is very likely already an undercount of what actually exists in the plant.

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Which Alkaloids Are Actually Documented Here

The genus Tabernaemontana is chemically close to Voacanga and Tabernanthe — the genus that includes iboga, source of ibogaine — and popular writing about crape jasmine sometimes borrows pharmacology wholesale from those relatives without checking whether the specific compound in question has actually been confirmed in this species. The table below is this page’s attempt to be precise about that, gathering names that appear across this Benefits leg’s four pages into one place.

• Coronaridine, voacangine, tabernaemontanine and conolidine — the four alkaloids the main topic page already names as the plant’s principal, confirmed constituents. Coronaridine and voacangine are iboga-type alkaloids with documented nicotinic-receptor and (for voacangine) ibogaine-precursor chemistry; conolidine is the trace bark alkaloid behind the non-opioid analgesic story covered on the Analgesic and Anti-Inflammatory Claims page.
• 19,20-dihydrotabernamine, 19,20-dihydroervahanine A, and 3′-R/S-hydroxyvoacamine — the three acetylcholinesterase-inhibiting bisindole alkaloids isolated from root and stem, covered in full on the Cognitive and Neuroprotective Claims page, confirmed by structural chemistry (NMR spectroscopy) directly from this species’ own tissue.
• Voacangine, catharanthine and O-acetyl vallesamine — the three alkaloids isolated from crape jasmine flowers behind the whole-extract antinociceptive effect, covered on the analgesic page. Catharanthine is shared chemotaxonomically with Catharanthus roseus; see that page for why this is interesting but not evidence of a chemotherapy application.
• Conophylline — a genuinely more complicated case, detailed in its own section immediately below.
• Tabernaricatines A–G and taberdines A–K — two large batches of newly described alkaloids (five plus two in a 2013 Journal of Natural Products paper; eleven in the 2021 Bioorganic Chemistry antifungal-synergist paper) isolated directly from this species’ aerial parts, confirming that phytochemical exploration of this plant is still actively finding new compounds as of the last few years.
• Heyneanine, voacristine, voacamine and descarbomethoxyvoacamine — isolated in the classic 1996 pharmacology paper from stems, alongside the bisindole alkaloid 19,20-dihydroervahanine A (independently found again a decade later in the root, above).

What this list is for: every specific claim on the other three Benefits pages in this leg can be traced to a named compound isolated directly from T. divaricata tissue, not assumed by analogy from a different Apocynaceae species. That precision matters most for the safety story that follows.

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Conophylline: A Case Study in Species Precision

Conophylline is worth its own section because it demonstrates exactly the kind of species-borrowing error this doctrine exists to catch — and because, once checked carefully, the citation turns out to hold up rather than fail.

The foundational pharmacology paper on conophylline’s antidiabetic activity, published in 2009 in Biomedicine & Pharmacotherapy, describes conophylline in its own introduction as “a vinca alkaloid from Ervatamia microphylla” — a related but genuinely different species. That sentence alone, read in isolation, would be a textbook case of borrowed evidence: crediting crape jasmine with a compound properly documented in a botanical relative. But the same paper’s own methods describe sourcing the actual test material — “crude conophylline preparations” — from the leaves of Tabernaemontana divaricata collected in Okinawa Prefecture, Japan. And independently, a 2003 phytochemistry paper in Organic & Biomolecular Chemistry, and again a 2013 paper in the Journal of Natural Products, both directly isolated and structurally confirmed conophylline from T. divaricata aerial-parts material. So the accurate statement is neither “conophylline belongs to crape jasmine” nor “citing conophylline for crape jasmine is a borrowing error” — it is that conophylline occurs in, and has been independently isolated from, both species, which is common among closely related plants sharing biosynthetic pathways, and any given study using the compound should be checked for which plant actually supplied the material, exactly as this page just did.

With that precision established, conophylline’s own pharmacology is genuinely interesting on two fronts. The 2009 rat study found that orally administered conophylline lowered fasting blood glucose and raised plasma insulin in streptozotocin-induced diabetic rats after fifteen days of repeated dosing, and produced a dose-dependent glucose reduction in Goto-Kakizaki rats (a genetic model of type 2 diabetes) over forty-two days — real, repeated-dose, oral efficacy data across two different diabetes models, which is more than most single-compound plant findings on this site can claim. Separately, the 2013 cytotoxicity paper found conophylline potently toxic to five different human cancer cell lines in vitro, with IC50 values (the concentration killing half the cells) ranging from 0.17 to 1.49 micromolar — genuinely potent, sub-micromolar activity. A more recent 2021 mechanism paper identified glutathione peroxidase 4 as a specific molecular target through which conophylline induces autophagy, giving this compound’s activity a defined biochemical handle rather than a black box.

Two real, preclinical, mechanistically grounded lines of evidence for one compound — and, characteristically for this plant’s entire literature, zero human data for either.

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Cytotoxicity to Cancer Cell Lines: Real Potency, Ambiguous Meaning

Beyond conophylline, several other named alkaloids and alkaloid-rich fractions from this plant show real cytotoxic activity against cancer cell lines in vitro. A 2022 study in the Journal of Ethnopharmacology found that an alkaloid-rich fraction of the leaf extract induced both apoptosis and autophagy in colorectal cancer cells, working through AMPK activation and mTOR pathway inhibition — two well-characterised cellular signalling nodes — and shrank tumours grown in mice, alone and in combination with the chemotherapy drug 5-fluorouracil. A related 2025 study found a similarly prepared leaf-extract fraction induced apoptosis in breast cancer cells through mitochondrial reactive-oxygen-species generation, reduced tumour growth in a mouse model both alone and combined with doxorubicin, and — more carefully than most of this literature — specifically reported little effect on normal cells and no significant toxicity in the treated mice overall.

Here is where doctrine and marketing part ways. A compound or fraction that is cytotoxic to cancer cells in a dish is, mechanistically, a compound that damages or kills cells — selectivity for cancer over normal tissue is not automatic, and most of this plant’s cytotoxicity literature did not test for it. The 2025 breast-cancer paper’s finding of preserved normal-cell viability is a genuinely more rigorous result than most of the surrounding literature, and it deserves credit for testing the question at all. It is still one study, using one specific fraction, in one specific cancer type, in mice, with no human trial anywhere near it. The same property being marketed as “anticancer potential” is, without a demonstrated therapeutic window, indistinguishable from general cytotoxicity — which is precisely why an unstandardised extract of this plant, taken on the theory that “it has anticancer alkaloids,” is not a reasonable substitute for oncology care, and could plausibly cause harm of exactly the kind these same studies were measuring.

The Hepatoprotective Counter-Finding

Not every finding in this plant’s toxicology-adjacent literature points toward caution, and it would be its own kind of inaccuracy to only report the alarming half. A 2014 study in BioMed Research International gave rats an ethanolic whole-plant extract of crape jasmine (200 or 400 mg/kg daily for 24 weeks) alongside two liver-damaging carcinogens, diethylnitrosamine and iron-nitrilotriacetate, and found the extract significantly reduced markers of liver damage (uric acid, bilirubin, and the liver enzymes AST, ALT and ALP), increased antioxidant markers, and reduced malondialdehyde, a marker of oxidative membrane damage — with the higher dose performing better, and results described as comparable to 5-fluorouracil, used here as the reference standard. Histopathology confirmed the protective effect.

This is worth stating plainly: this plant’s alkaloid richness does not automatically imply liver toxicity, and the one dedicated hepatoprotection study found the opposite of harm. It remains a single, unreplicated animal study using a whole-plant extract rather than any of the specific alkaloids discussed elsewhere on this page, and it does not establish human liver safety — but naming what a herb is not shown to do is as much a part of an accurate profile as naming what it is.

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A Toxicity Screening Number, and Why It Stops There

One paper already discussed on the analgesic page for its pain-relief comparison also ran a standard preliminary toxicity screen: brine-shrimp lethality testing, in which increasing concentrations of an extract are applied to brine-shrimp larvae and mortality is recorded. Crape jasmine leaf extract produced an LC₅₀ (the concentration lethal to half the test population) of 200 µg/mL and an LC₉₀ (lethal to ninety percent) of 350 µg/mL — a potency profile broadly comparable to the other three plants tested in the same paper. Brine-shrimp lethality is a real, standard, inexpensive first-pass toxicity screen widely used in natural-products research, and a low LC50 (meaning toxicity at a low concentration) is a genuine reason for caution.

What this page refuses to do with that number: turn it into a human dose. Brine-shrimp lethality correlates loosely with general bioactivity and toxicity, but converting a microgram-per-millilitre concentration lethal to a small aquatic crustacean into any statement about a safe or unsafe human oral dose would require pharmacokinetic, absorption and species-scaling data that does not exist for this plant. No dose appears anywhere in this Benefits leg for exactly this reason — not because the topic is being avoided, but because a confident number would be a guess dressed up as a finding.

Voacangine, Ibogaine, and the Documented Cardiac Risk

This is the plant’s most serious safety story, and it deserves the same precision the rest of this page has tried to apply.

What is confirmed in this species: voacangine is a documented constituent of T. divaricata, isolated directly from its tissue in multiple studies cited across this Benefits leg. Chemically, voacangine sits one defined synthetic step from ibogaine, and is the standard starting material used in the ibogaine trade for semisynthesis — a well-established fact of organic chemistry, true of voacangine regardless of which plant supplied it.

What is not directly confirmed in this species: the specific pharmacology research on cardiac risk — hERG potassium-channel blockade, QT-interval prolongation, and documented fatal arrhythmia — has been conducted on ibogaine itself and on voacangine extracted from other Tabernaemontana species (Mexican Tabernaemontana species, and Tabernaemontana arborea specifically) and from Voacanga africana, not from T. divaricata material directly. A 2016 Cardiovascular Toxicology paper established that iboga-type alkaloids as a class block the hERG potassium channel — the same channel underlying most drug-induced fatal arrhythmias — providing the specific molecular mechanism. A 2016 case report and literature review in Therapeutic Advances in Psychopharmacology documented cardiac arrest and death temporally associated with ibogaine use, and a separate 2016 Clinical Toxicology review assessed the broader fatality and adverse-event literature for ibogaine specifically.

How to read the two together, honestly. This is not a report of T. divaricata poisoning a named person — no such case report turned up in the literature searched for this leg. It is a class-level, mechanism-level rationale: a defined chemical relative of a documented cardiotoxin, confirmed present in this plant, acting (very plausibly, by chemical similarity) on the same ion channel responsible for the documented deaths in the closely related compound. That is precisely the standard the main topic page already applies when it declines to give a dose — not because this species has a body count, but because the chemistry connecting it to one that does is real, specific, and one step long rather than a vague family resemblance.

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Why a Marker Compound Cannot Confirm What Is in a Bottle

Voacangine and coronaridine are not unique to crape jasmine — both are shared iboga-type alkaloids documented across Tabernaemontana, Voacanga and Tabernanthe species, per the 2021 genus-wide review of Tabernaemontana alkaloid chemistry. A product “standardised” or tested to show the presence of either compound cannot, on that basis alone, be confirmed as made from T. divaricata rather than a related genus — the same limitation the doctrine on this site has flagged for other herbs sharing marker compounds with close relatives. A marker-compound assay is a potency and purity check; identity requires botanical or DNA-based confirmation, which is a different and less commonly performed test. This matters here specifically because “standardized to voacangine” sounds like a precise, reassuring product claim, and by itself it is not one.

What This Plant Is Not Documented to Do

Naming what a herb is not guilty of is as much a part of accuracy as naming its real risks, and a few things are worth stating clearly here rather than leaving to inference.

• No documented cardiac glycoside content. Unlike its family-mate oleander, crape jasmine’s chemistry is indole alkaloids, not cardiac glycosides — a different toxin class acting on a different target. The mechanism of its most serious cardiac concern (hERG channel blockade via iboga-type alkaloids) is real but distinct from oleander’s.
• No case reports of human hepatotoxicity turned up in the literature searched for this leg, and the one dedicated liver study found a protective rather than harmful effect, discussed above.
• No documented case report of this specific species causing a fatal or near-fatal human poisoning appeared in the literature searched for this page — the cardiac risk discussed above is a mechanism-level, class-level rationale for caution, not a body count for this species. This does not mean the plant is safe to ingest; it means the specific evidence takes the form of chemistry and class-level risk rather than accumulated case reports, most plausibly because this is an ornamental garden plant that is rarely deliberately consumed rather than because it has been tested and cleared.

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Evidence Ledger for This Page

1. Sixty-six named alkaloids confirmed in this species specifically. Tier: well-documented structural chemistry, an actively growing count as of recent (2019–2024) publications.
2. Cytotoxicity to cancer cell lines in vitro (conophylline and alkaloid-rich fractions). Tier: preclinical, multiple independent groups, real sub-micromolar potency for specific compounds — and simultaneously a general toxicity signal without therapeutic-window data in most of the work.
3. Antidiabetic activity of conophylline. Tier: preclinical, real oral efficacy across two rat models, repeated dosing. Compound also independently documented in a related species.
4. Hepatoprotective activity of whole-plant extract. Tier: single study, positive, unreplicated.
5. hERG channel blockade and cardiac arrhythmia risk from iboga-type alkaloids. Tier: well-documented for ibogaine and for voacangine sourced from other Tabernaemontana/Voacanga species; a class-level, mechanism-level rationale for caution around this species’ own confirmed voacangine content, not a direct species-specific case report.
6. Brine-shrimp toxicity screening. Tier: single preliminary screen, real number, not extrapolable to a human dose.
7. Human safety or toxicology data for this plant, in any preparation, at any dose. Tier: absent. This is the fact that governs how every other row on this ledger should be read.

Practical Guidance

• Nothing in this article supports self-administering any preparation of crape jasmine — leaf, root, bark, latex, flower or fruit — for any indication. No dose has been established for any use, and none is given anywhere on this site.
• Given the confirmed cardiac-risk mechanism, anyone with a personal history of arrhythmia, a prolonged QT interval, or who takes QT-prolonging medication should regard this plant as categorically off-limits, alongside the cholinergic-interaction caution covered on the Cognitive and Neuroprotective Claims page.
• If a child or pet has ingested any part of this plant, treat it as a poisoning and contact poison control or emergency veterinary services immediately — see the main topic page’s safety section for full guidance.
• A supplement or product claiming to be “standardized” to voacangine or coronaridine content has not, by that claim alone, established that it is actually made from this species.

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Key Research Papers

1. Pratchayasakul W, Pongchaidecha A, Chattipakorn N, Chattipakorn S. Ethnobotany & ethnopharmacology of Tabernaemontana divaricata. Indian Journal of Medical Research, 2008. Find on PubMed.
2. Naidoo CM, Naidoo Y, Dewir YH, Murthy HN, El-Hendawy S, Al-Suhaibani N. Major bioactive alkaloids and biological activities of Tabernaemontana species (Apocynaceae). Plants, 2021. Find on PubMed.
3. Bao MF, Yan JM, Cheng GG, Li XY, Liu YP, Li Y, Cai XH, Luo XD. Cytotoxic indole alkaloids from Tabernaemontana divaricata. Journal of Natural Products, 2013. Find on PubMed.
4. Kam TS, et al. Biologically active indole and bisindole alkaloids from Tabernaemontana divaricata. Organic & Biomolecular Chemistry, 2003. Find on PubMed.
5. Fujii M, Takei I, Umezawa K. Antidiabetic effect of orally administered conophylline-containing plant extract on streptozotocin-treated and Goto-Kakizaki rats. Biomedicine & Pharmacotherapy, 2009. Species-precision case study — see above. Find on PubMed.
6. Dutta N, Pemmaraju DB, Ghosh S, et al. Alkaloid-rich fraction of Ervatamia coronaria sensitizes colorectal cancer through modulating AMPK and mTOR signalling pathways. Journal of Ethnopharmacology, 2022. Find on PubMed.
7. Majumder C, Manna A, Halder S, Roy S, Mandal SC, Jana K, Pal M. Indole-alkaloid-rich fraction of Ervatamia coronaria leaf extract regresses breast cancer by inducing apoptotic cell death. Biotechnology Reports, 2025. Find on PubMed.
8. Poornima K, Chella Perumal P, Gopalakrishnan VK. Protective effect of ethanolic extract of Tabernaemontana divaricata against DEN and Fe-NTA induced liver necrosis in Wistar Albino rats. BioMed Research International, 2014. Find on PubMed.
9. Khan MA, Islam MT. Analgesic and cytotoxic activity of Acorus calamus L., Kigelia pinnata L., Mangifera indica L. and Tabernaemontana divaricata L. Journal of Pharmacy & Bioallied Sciences, 2012. Source of the brine-shrimp toxicity screen. Find on PubMed.
10. Alper K, Bajaj P, Kotbi N, et al. hERG blockade by iboga alkaloids. Cardiovascular Toxicology, 2016. Find on PubMed.
11. Meisner JA, Wilcox SR, Richards JB. Ibogaine-associated cardiac arrest and death: case report and review of the literature. Therapeutic Advances in Psychopharmacology, 2016. Find on PubMed.
12. Litjens RP, Brunt TM. How toxic is ibogaine? Clinical Toxicology, 2016. Find on PubMed.

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Connections

• All Herbs
• Crape Jasmine (Main Page)
• Crape Jasmine Benefits Hub
• Wound Healing and Antimicrobial Claims
• Analgesic and Anti-Inflammatory Claims
• Cognitive and Neuroprotective Claims
• Toxins
• Type 2 Diabetes

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