The document explores the relationship between poisonous plants and their medicinal uses through medical ethnobotany, detailing how various plants like cassava, pokeweed, and deadly nightshade can serve both as poisons and medicines depending on processing and dosage. It highlights historical uses, traditional remedies, and the chemical properties of these plants, illustrating the complex interplay of toxicity and therapeutic benefits while providing examples from history and mythology. Ultimately, the distinction between a poison and a medicine often hinges on dose and intent.

1. Deadly Cures:
Medical discoveries from poisonous plants
Cassandra L. Quave, Ph.D.
Assistant Professor
Department of Dermatology (SOM)
Center for the Study of Human Health (ECAS)
Curator
Emory University Herbarium
E-mail: cquave@emory.edu
Website: http://etnobotanica.us/
Twitter: @QuaveEthnobot
Deadly Nightshade

2. Virtue itself turns to vice, being misapplied,
And vice sometimes by action dignified.
Within the infant rind of this small flower,
Poison hath residence, and medicine power.
-William Shakespeare, Romeo and Juliet

3. Outline
• Medical Ethnobotany
• Why do plants make poisons?
• Poison… or food?
• Poisons in history, legend and myth
• Medical discoveries from poisonous plants
• Poisonous plants in the home and yard

4. The Science of Ethnobotany
• Ethnobotany (from
ethnology, study of
culture, and botany, study
of plants) is the scientific
study of the relationships
that exist between
peoples and plants.
• Ethnobotany is the
science of survival.

5. Ethnobotany is Multidisciplinary
Ethnobotany
Botany
Chemistry
Microbiology
Anthropology
Linguistics
Pharmacology
• Medicine
• Conservation
• Food security

6. Deter other
plant
species
from
growing
nearby
Fight off
microbial
invasion &
infection
Attract pollinatorsDefense against
herbivory
Why do plants make poisons?

7. Poisons in Human History
• Early humans likely
experienced much poisoning
in the search for new foods
• One function of early
agriculture was to select for
more palatable (less bitter,
less poisonous) plant
variants
• Food processing to remove
poison also important
Cassava

8. Cassava: Sweet and Bitter Manioc
• Manihot esculenta Crantz,
Euphorbiaceae
▫ Starchy tuber is the main source
of carbohydrates in the tropics
▫ Tuber is filled with poisonous
cyanogenic glycosides and
hydrogen cyanide (HCN)
 A dose 40 mg of pure cassava
cyanogenic glycoside is sufficient
to kill a cow.
▫ Tuber is processed to remove
the poison (soaking, boiling,
fermentation)
Drinking masato – fermented cassava beverage.
Peruvian Amazon

9. Poke Weed…
Poison, Medicine or Food?
• Phytolacca americana L., Phytolaccaceae
Young plant (young leaves only) eaten as
“poke salet”
• Contains phytoagglutinins (pokeweed
mitogens), but can be denatured with
processing (heat labile)
▫ Boiled in water, water tossed several times
(thrice boiled)
• Used in Native American traditional remedies for
ulcer, rheumatism, kidney problems
• Mature plants (esp. roots) are highly toxic if
consumed.
• Symptoms include:
▫ convulsions, diarrhea, headache, seizures, rapid
pulse, difficulty breathing, stomach pains,
vomiting, weakness

10. Poisonous Gymnosperms
• All cycads and zamias have poisonous fleshy seeds
▫ BUT… if the azoxy alkaloids are washed out, they can be eaten (or flour made
from them), as was common practice among the Seminole tribe of Florida
Fern palm
Cycas circinalis L.,
Cycadaceae
False sago palm
Dioon edule
Lindl.Zamiaceae
Coontie
Zamia integrifolia L. f.,
Zamiaceae

11. Poisons and the Criminal Arts
• Agrippina (19-59 AD)
▫ Empress and wife of Emperor
Claudius and mother of Nero
▫ Used poisonous mushrooms to
kill Lollia Paulina, Marcus
Sianus, and her husband
Claudius, among others

12. The execution of Socrates – Plato’s account
Socrates walked about, and presently, saying that his legs
were heavy, lay down on his back--that was what the
man recommended. The man--he was the same one who
had administered the poison--kept his hand upon
Socrates, and after a little while examined his feet and
legs, then pinched his foot hard and asked if he felt it.
Socrates said no. Then he did the same to his legs, and
moving gradually upward in this way let us see that he
was getting cold and numb. Presently he felt him again
and said that when it reached the heart, Socrates would
be gone.
The coldness was spreading about as far as his waist
when Socrates uncovered his face, for he had covered it
up, and said--they were his last words--Crito, we ought
to offer a cock to Asclepius. See to it, and don't forget.

13. Poison Hemlock
Conium maculatum L., Apiaceae
• European poison hemlock
made famous by Socrates’
execution (contains toxic
pyridine alkaloids)
• Active Compound:
▫ Cicutoxin, in root and above-
ground parts: is a violent
convulsant that acts directly
on the central nervous system
• Symptoms:
▫ 2-3 cm section of root can kill
an adult

14. Medicine or Poison?
The distinction between poison and medicine often
comes down to two simple points: dose and intent.
“Natural” does not always = safe!!

15. Poisons and the criminal arts
• Cleopatra (51-30 BC)
• Tested poisons on her
slaves
▫ Henbane
 Hyoscyamus niger L.,
Solanaceae
▫ Belladonna; Deadly
nightshade
 Atropa belladonna L.,
Solanaceae
▫ Poison nut
 Strychnos nux-vomica L.,
Loganiaceae

16. Deadly Nightshade
Atropa belladonna L., Solanaceae
• It was used in traditional treatments
for centuries for an assortment of
conditions including
▫ Headache
▫ Menstrual symptoms
▫ Peptic ulcer disease
▫ Inflammation
▫ Motion sickness
▫ Mydriatic (pupil dilator)
• Plant occasionally used as a
recreational drug because of the vivid
hallucinations and delirium that it
produces.
▫ Unpleasant hallucinations. Recreational use is
considered extremely dangerous because of the
high risk of unintentional fatal overdose.
▫ The CNS effects of atropine include memory
disruption, which may lead to severe confusion

17. Deadly Nightshade
Atropa belladonna L., Solanaceae
• Toxicity
▫ Berries are attractive & taste sweet, but
consumption can be fatal, esp. in
children
▫ Anti-cholinergic
▫ Symptoms include: dilated pupils,
sensitivity to light, blurred vision,
tachycardia, loss of balance, staggering,
headache, rash, flushing, severely dry
mouth and throat, slurred speech,
urinary retention, constipation,
confusion, hallucinations, delirium, and
convulsions

18. Deadly Nightshade
Atropa belladonna L., Solanaceae
• Source of atropine
▫ Useful in management of
bradycardia following a myocardial
infarction
▫ Used in management of hypotension
that is associated with slow heart
rate
▫ Eyedrops or ointment to open iris for
eye exams, surgical procedures, and
to treat anterior uveitis
▫ Antidote for cholinergic crisis (such
as induced by physostigmine or
nerve gas)
• Source of hyoscamine and
scopolamine – used in functional
gastric disorders

19. Poison nut
Strychnos nux-vomica L., Loganiaceae
• Active Compound:
▫ Indole alkaloids (strychnine
and brucine) from dried ripe
seeds; all parts contain
strychnine
• Symptoms:
▫ Agitation, muscle spasms,
convulsions
▫ Extremely toxic, strychnine is
fatal to humans at doses of 60-
90 mg

20. Henbane
Hyoscyamus niger L., Solanaceae
• Traditionally used in combination
with Atropa belladonna and Datura
spp. for pyschoactive effects
(hallucinogen) in witches’ brew
• Source of hyoscamine and
scopolamine
• Toxicity:
▫ Symptoms include hallucinations,
dilated pupils, restlessness and
flushed skin
Scopolamine/Hyoscine Hyoscamine

21. Jimsonweed
Datura stramonium L., Solanaceae
• Used as recreational
psychoactive drug – users often
unaware of toxicity/poisonous
nature of plant
• Active Compound:
▫ Scopalamine: most found in leaves,
unripe capsules, especially seeds
• Symptoms:
▫ Even small amounts fatal;
symptoms similar to Atropa
belladonna (anti-cholinergic;
flushed skin, dilated pupils, dry
mouth, delirium, death from
respiratory failure)

22. Scopolamine (aka Hyoscine)
• Medicinal applications:
▫ Remedy for motion sickness
 Oral dose or by patch
▫ Postoperative nausea/vomiting
▫ Gastrointestinal spasms
• Toxicity:
▫ Symptoms include: tachycardia,
arrhythmia, blurred vision,
photophobia, urinary retention, dry
mouth, skin reddening
• Overdose/poisoning can be treated with
physostigmine, a plant compound from
the Calabar bean (Physostigma
venenosum)

23. Hyoscyamine
• Medicinal uses:
▫ Treatment of certain GI disorders
(peptic ulcers, irritable bowel
syndrome, colic) and control some
of the symptoms of Parkinson’s
disease
• Toxicity
▫ Symptoms include headache,
nausea, vomiting, disorientation,
hallucinations, euphoria, sexual
arousal and short-term memory
loss

24. Calabar bean
Physostigma venenosum Balf. f., Fabaceae
• Calabar bean
▫ Historical ‘ordeal’ bean in the Calabar area
of Nigeria
▫ Given to people on trial – if died, were
guilty, if vomit & live, not guilty
• Physostigmine
▫ Medicinal uses: myasthenia gravis,
glaucoma, Alzheimer's disease and delayed
gastric emptying
▫ Antidote of choice for Datura stramonium
& Atropa belladonna poisoning
▫ Toxicity: cholinergic syndrome (SLUDGE:
salivation, lacrimation, urination,
defecation, gastrointestinal upset, vomiting)

25. Poisons in Mythology
• Plant teratogen causes Cyclopia!
• Veratrum album L., V. californicum
Durand and V. viride Aiton,
Melanthiaceae [false hellebore] –
case of mistaken identity with other
hellebore (Helleborus spp.,
Ranunculaceae) used in ancient
Greek medicine as purgative
• Consumption during early pregnancy
(in humans and other animals – esp.
common in sheep) results in cyclopia
▫ Single eye, often missing nose
▫ Usually stillborn
• Responsible compound: cyclopamine

26. False Hellebore/ White
Hellebore
Veratrum album L.,
Melanthiaceae
Hellebore/ Black Hellebore
Helleborus niger L.
Ranunculaceae

27. Groundsels; Ragworts
Senecio spp., Asteraceae
• Mistaken identity – confused
with a Gnaphalium spp.&
included in herbal remedy for
colds
• Active Compound:
▫ Hepatotoxic pyrrolizidine
alkaloids
• Symptoms:
▫ Ingestion results in acute
illness and death in livestock
and humans
Senecio flaccidus L. (Hook)

28. Oleander
Nerium oleander L., Apocynaceae
• Examples of poisoning
events:
▫ Ingestion after confusion
with eucalyptus
▫ Ingestion by children
▫ Suicide attempts
• Active Compound:
▫ Cardioactive glycosides;
oleandrin is the main
glycoside from leaves
• Symptoms:
▫ Ingestion results severe
vomiting, bloody diarrhea,
irregular heartbeat,
drowsiness, unconciousness,
respiratory paraylysis, fatal
Advisory Council, Zayed Complex for Herbal Research and
Traditional Medicine, Abu Dhabi, UAE

29. Ginkgo: Poison or Medicine? Both?
• Ginkgo biloba L., Ginkgoaceae
• Leaves used in herbal supplements for improved cognitive function
• Seeds contain a neurotoxin:
▫ 4-O-methyl pyridoxine (ginkgotoxin)
 Interferes with amino acid metabolism
 Results in convulsions and death (27% lethality)
▫ Fruit pulp causes allergic contact dermatitis
Hortus Botanicus in Leiden, The Netherlands. Oldest Ginkgo in Europe.
Ginkgo fruits

30. Autumn crocus; Meadow saffron
Colchicum autumnale L., Colchicaceae
• Colchicine derived from this
plant used medicinally to treat
gouty arthritis
• Active Compound:
▫ Colchicine & other alkaloids
▫ Highest concentration is in seeds
and corm
 Amount of colchicine in 2-3 seeds can
kill
• Poisoning Symptoms:
▫ Burning of throat & stomach,
vomiting, purging, weak-quick
pulse, kidney failure, respiratory
failure, often fatal, flowers have
been fatal to children

31. Colchicine
• 1st isolated in 1820
• Used as alternative gout treatment for those
unable to tolerate NSAIDs
• How it works: it inhibits deposition of uric acid
(urate crystals), raises tissue pH by inhibiting
glucose oxidation, reducing production of lactic
acid in leukocytes
• Plant extract not used because colchicine is highly toxic, and
dose must be controlled
• History
▫ 1st described by Dioscorides as a gout treatment in De
Materia Medica
▫ Used in ancient Islamic medicine & in Europe;
Benjamin Franklin in USA used it to treat his gout
▫ 2009 – FDA approved for gout treatment Colchicum autumnale
(Colchicaceae)
Pain of gout

32. Draining of dropsical fluid, 1741 Digitalis purpurea L.
Common Foxglove

33. Foxglove
Digitalis purpurea L., Plantaginaceae
• 1700’s British folk medicine
• William Withering published book in
1785 based on the accounts of an “old
woman in Shropshire”
• Used in treatment of dropsy
• Still used for congestive heart failure
• Led to discovery of digitoxin and
digoxin, found in leaves, seeds and
flowers
• Toxicity: therapeutic dose is close
to the toxic dose
▫ Poisoning can occur from the plant or
overdose of medication
▫ Death from Digitalis poisoning from
ventricular fibrillation
▫ Side effects: nausea, fatigue, salivation,
severe headache, irregular heartbeat and
pulse, toxicity in combo with calcium,
sudden death
Digitoxin
Digoxin

34. Pacific Yew
Taxus brevifolia Nutt., Taxaceae
• History of use in Native American traditional
medicine: respiratory, dermatological,
gastrointestinal, and urological applications
• Toxicity:
• Taxines are cardiotoxic
• Lethal dose: 4-20 mg/kg
• Rapid absorption from GI tract to circulatory system
• Affects sodium-potassium transport
• Sudden death occurs with trembling, labored
breathing, and collapse
• Most deaths in animals that forage on leaves, human
deaths rare
• Taxol (Paclitaxel)
▫ Taxane diterpene discovered in 1960s NCI screen
 Showed strong activity against solid tumors,
melanoma, and leukemia models
 Taxol concentations are low; most toxicity
attributed to the taxines
▫ It took 30+ years from discovery to approval
Paclitaxel

35. • One BIG problem – very low
yield in plant (0.004%)
▫ Solution: semi-synthesis of taxol by
conversion of metabolites available
in larger quantities in needles of
English Yew (Taxus baccata)
 Needles were a renewable source –
no need to kill the tree by removing
bark
• Taxol (Bristol Meyers
Squibb) approved in USA in
1993
▫ Treatment for ovarian cancer
and secondary treatment for
breast and non-small cell lung
cancers
• Docetaxel was approved in
1995
▫ marketed as Taxotere
▫ more water soluble than taxol
Breast and ovarian cancer
• Abraxane – paclitaxel
bound to albumin, approved
in 2005
▫ Breast cancer unresponsive to
other chemotherapies
Taxus baccata (Taxaceae) – English Yew
Taxol

36. Docetaxel (Taxotere®)
• Semi-synthetic analogue of
paclitaxel
• Anti-mitotic chemotherapy
(interferes with cell division)
• FDA approved for:
▫ locally advanced or metastatic breast
cancer, head and neck cancer, gastric
cancer, hormone-refractory prostate
cancer and non small-cell lung cancer
▫ Maybe used alone or in drug combos
• Disadvantage: prone to cellular drug
resistance
• Side effects:
▫ Alopecia, neutropenia, anemia

37. Mayapple; American Mandrake
Podophyllum peltatum L., Berberidaceae
• Long history of traditional use of
rhizomes as medicine by Native
Americans
▫ Dried & made into powder, then
 eaten or drunk as laxative or
antihelmintic
 poultice applied to warts & skin
growths
• Currently plant extracts used as
topical treatment for warts & skin
growths
• Toxicity:
▫ Fruits are poisonous if eaten in large
amounts. Leaves and roots poisonous
if consumed. Podophyllotoxin
(medicinal compound) is poisonous if
taken internally.

38. Etoposide
• Marketed as VePesid®
▫ Small cell lung cancer, testicular cancer &
lymphomas
• antineoplastic or cytotoxic chemotherapy drug
• It is a semisynthetic derivative of
podophyllotoxin used in the treatment of certain
cancers:
▫ Testicular, bladder, prostate, lung, stomach, and uterine,
cancers. Hodgkin's and non-Hodgkin's lymphoma,
mycosis fungoides, Kaposi's sarcoma, Wilm's tumor,
rhabdomyosarcoma, Ewing's sarcoma, neuroblastoma,
brain tumors
• Administered orally
• Side Effects:
▫ Low white blood cell count, Low platelet count, Hair loss ,
Menopause, Loss of fertility, Nausea and vomiting, Low
blood pressure

39. Teniposide
• Teniposide marketed as Vumon®
 brain tumors, childhood acute leukemia
• Administered by injection
• Semisynthetic derivative of
podophyllotoxin
▫ Used in combination with other approved
anticancer agents for induction therapy in
patients with refractory childhood acute
lymphoblastic leukemia.
• Side-Effects
▫ Severe myelosuppression with resulting
infection or bleeding may occur;
hypersensitivity reactions

40. (+)-Tubocurarine
Dart Poisons

42. The varzea

44. Dart Poisons
• Neuromuscular blocking agents
▫ Isoquinoline & indole alkaloids
▫ (+)-tubocurarine leading agent
▫ Competes with acetylcholine for
cholinergic receptors at the motor
endplate, preventing formation of
action potential
▫ Causes death by paralyzing the
respiratory system, causing
asphyxiation
• Loganiaceae & Menispermiaceae families
are primary plant sources
▫ Strychnos spp. (Loganiaceae)
▫ Chondrodendron tomentosum Ruiz &
Pav., Menispermiaceae (curare vine)
Chondrodendron tomentosum

45. Curare vine
Chondrodendron tomentosum Ruiz & Pav., Menispermiaceae
• (+)-Tubocurarine
▫ Skeletal muscle relaxant
▫ Helped to revolutionize surgery – less
anesthesia was necessary to perform
operations
▫ Acts as a long-duration, non-depolarizing
neuromuscular blocking agent that is a
competitive antagonist of nicotinic
neuromuscular acetylcholine receptors
▫ Rarely used today as an adjunct for clinical
anesthesia because safer alternatives such as
cisatracurium and rocuronium are available.

46. Useful poisonous plants in the Mediterranean
Pantelleria

48. Basket weaving for Agricultural & Fishing Tools
Euphorbiaceae

49. Daphne gnidium L., Thymelaeaceae
Ethnobotanicals uses:
• Insect repellent (ticks and
fleas)
• Hemostatic

50. Daphne gnidium poisoning
• Leaves are the most toxic
• Symptoms include:
▫ Headache
▫ Shivering
▫ Paleness
▫ Pupil dilatation
▫ Mouth and lips swelling
▫ Diarrhea and digestive
spasms
▫ Convulsion
▫ Pulmonary disorders
▫ Death

51. Castor bean
Ricinus communis L., Euphorbiaceae
• Castor oil extracted from seeds is
used medicinally as laxative – but
eating the seeds can kill
• Active Compound:
▫ Ricin: a highly poisonous
phytotoxin (plant protein)
▫ FBI lists ricin as the 3rd most
poisonous substance known
 3,000 x more toxic than cyanide
 12,000 x more toxic than
rattlesnake venom
• Toxicity:
▫ Symptoms include nausea,
muscle spasms, purgation,
convulsions, and death
(accompanied by hemorrhage,
GI edema and degeneration of
kidneys)

52. Poisonous plants in the home and yard

53. Calcium oxalate is found in many
house plants
• Symptoms of poisoning:
▫ Dermatitis
▫ Swelling of the tongue,
can lead to asphyxiation
▫ Irritation/burning in the
mouth
▫ Development of kidney
stones (edible plants i.e.
Rumex spp., dock)
▫ Toxic to humans and pets

54. Poisonous house plants from the
Araceae family contain calcium oxalate
Philodendron
Philodendron spp.
Dumbcane
Dieffenbachia maculata
Caladium; Elephant Ear
Caladium spp.

55. Abrus precatorius L., Fabaceae (rosary pea;
jequirity bean)
• Toxic effect from chewing the seeds
• Active Compound:
▫ Abrin (phytotoxin similar to ricin) &
abric acid from thoroughly chewed
seeds
• Symptoms:
▫ Gastrointestinal distress
▫ Fatal to humans and animals

56. Rhus Dermatitis
• Rhus = group of plants responsible for more cases of Allergic
Contact Dermatitis (ACD) than any other allergen
• Rhus is the botanical synonym for Toxicodendron in the
Anacardiaceae family
• Pentadecylcatechol is an allergin found in the plant sap
(oleoresin)
 Poison ivy
 Poison oak
 Poison sumac
 Mango (rind)
 Lacquer tree
 Cashew nut
 Indian marking nut

57. Rhus Dermatitis Plants
• Anacardiaceae
▫ Toxicodendron radicans (L.) Kuntze
[Poison Ivy]
▫ Toxicodendron diversilobum (Torr.
& A. Gray) Greene [Poison Oak]
▫ Toxicodendron vernix (L.) Kuntze
[Poison Sumac]
▫ Mangifera spp. [Mango]

58. Rhus Dermatitis Plants
• Anacardiaceae
▫ Toxicodendron vernicifluum
(Stokes) F.A. Barkley [Lacquer Tree]
▫ Anacardium occidentale L. [Cashew
Nut]
▫ Semecarpus anacardium L. f.
[Indian marking nut]

59. Conclusions
• There are many
poisonous plants that
actually serve an
important role to many in
terms of:
▫ Food security
▫ Medicine
▫ Fishing tools
▫ Hunting tools
• Poisonous chemicals can
be concentrated in
specific plant tissues
• In most cases, there is a
thin line between poison
and medicine and it all
comes down to 2 key
factors: dose and intent.

60. Acknowledgements
• Emory University Herbarium
Staff and Volunteers
• Philanthropic donation
• How to help the Emory
Herbarium:
▫ Support our educational
outreach and research
mission! We are seeking
donations of funds, books,
ethnobotanical objects,
and historic herbaria
collections. Visit our
website for more info:
https://scholarblogs.emor
y.edu/emoryherbarium/