Plant Poisons: Abrus, Ricinus, Datura, Aconite and Oleander

Plant poisons account for a non-trivial share of homicidal and suicidal poisoning across India because source material is freely available and Ayurvedic preparations sometimes contain underprocessed material. The workflow (suspicion, viscera collection, classical extraction by Stas-Ottocolour test, TLC, LC-MS) binds the family grid together.

1. Toxalbumins / lectins. Abrin fromAbrus precatorius(jequirity, rati) and ricin fromRicinus communis(castor, arandi). Two-chain ribosome-inactivating proteins. A-chain inactivates the 60S subunit, B-chain binds galactose. Lethal at microgram-per-kilogram doses if parenteral.
2. Tropane alkaloids. Atropine, hyoscyamine, scopolamine fromDatura stramonium / metel / fastuosa(dhatura) andAtropa belladonna. Competitive muscarinic blockers. Anticholinergic syndrome.
3. Diterpene alkaloids. Aconitine and mesaconitine fromAconitum napellusandA. ferox(bachhnag, mitha visha). Persistent activation of voltage-gated sodium channels. Cardiotoxic.
4. Cardiac glycosides. Oleandrin fromNerium oleander(kaner) and thevetin fromCascabela thevetia / Thevetia peruviana(pila kaner, yellow oleander). Na+/K+-ATPase inhibitors.
5. Indole alkaloids. Strychnine and brucine fromStrychnos nux-vomica(kuchla). Glycine-receptor antagonists. Tetanic convulsions, opisthotonus, risus sardonicus.

The syllabus also expects awareness of cyanogenic glycosides(amygdalin in bitter almonds, linamarin in cassava and bamboo shoots) and capsaicin in chillies. Opium-poppy alkaloids belong to the stimulants, narcotics and opiatesbullet.

Abrin (Abrus precatorius). Scarlet seeds with a sharply demarcated black hilum (the "rati" goldsmith's weight). The seed coat is impermeable, so whole swallowed seeds usually pass through harmlessly; crushed or punctured seeds release abrin, a 65 kDa type-2 ribosome-inactivating protein. The B-chain binds galactose on enterocytes (or, in historical "sui" cattle cases, on the tissue surrounding a thorn needle driven under the skin), the A-chain depurinates A4324 of 28S rRNA in the 60S subunit. Protein synthesis stops. Latency 12 to 72 hours, then haemorrhagic gastroenteritis, hepatic and renal failure.

Ricin (Ricinus communis). Mottled brown castor seeds with a prominent caruncle. The textbook type-2 RIP (66 kDa, A + B chains, same depurination). LD50 about 1 to 5 micrograms per kilogram by injection or inhalation; oral toxicity an order of magnitude lower. The 1978 Markov umbrella-tip assassination is the canonical case. CWC Schedule 1 substance.

Detection. No useful colour test. Confirmation is by ELISA against the A or B chain, SDS-PAGE plus Western blot, or LC-MS/MS peptide mapping after tryptic digestion (signature peptide VTLTCEGSNYK for ricin). Powder microscopy of crushed seed shows oil droplets, starch grains, and diagnostic seed-coat fragments.

Datura species (D. stramonium, D. metel, D. fastuosa)carry atropine, hyoscyamine and scopolamine in every part of the plant, highest in seeds and roots. Datura is the single most casework-relevant plant poison in India because of the long-running "highway robbery" pattern: a stranger offers a traveller food laced with ground Datura seed; the victim develops the full anticholinergic syndrome (dry mouth, mydriasis, tachycardia, delirium), passes out, and is robbed. Criminal use is charged under BNS Section 328(administration of poison or stupefying substance with intent), the successor to IPC Section 328.

Seed identification. Datura seeds are flat, reniform (kidney-shaped), 3 to 4 mm, dark brown to black, with a finely pitted surface. Pitted seed-coat sclereids and the curved embryo are diagnostic under low-power microscopy.

Chemical detection. The Vitali-Morin test is the classical colour test: evaporate the alkaloid extract with fuming nitric acid, cool, add alcoholic potassium hydroxide. A violet colour indicates atropine or hyoscyamine. The reaction depends on the tropic-acid moiety, so it is negative on cocaine and weak on scopolamine (which has scopic acid). Confirmation is by TLC (silica gel, methanol-ammonia, Dragendorff's reagent) and GC-MS or LC-MS/MS on alkaline-extracted viscera. The signs, symptoms and antidotes of common poisonschapter covers clinical management (physostigmine is the specific antidote).

Aconitum napellus and A. ferox are the most toxic Indian aconites. The dried tuber (bachhnag, mitha visha) is a small conical brown root with a hairy crown of scale leaves. Processed aconite appears in Ayurvedic preparations after detoxification (boiling in cow's milk or urine for hours); most fatal poisonings trace to underprocessed Ayurvedic doses or accidental ingestion of the tuber mistaken for a culinary root.

Mechanism. Aconitine and mesaconitine bind site 2 of the voltage-gated sodium channel and prevent inactivation. The channel stays open, sodium flows continuously, producing persistent depolarisation, ectopic cardiac firing, and refractory ventricular arrhythmia. Onset within minutes, death within 2 to 6 hours.

Clinical course. Tingling and numbness of lips and tongue, paraesthesia of the limbs, salivation, vomiting, hypotension and ventricular arrhythmia. No specific antidote; amiodarone or magnesium for the arrhythmia is standard ICU response.

Detection. Tanret's reagent (KI + HgI2 in dilute acetic acid) gives a yellowish-white precipitate with aconitine. The historical taste test (tuber paste on the tongue, producing instant numbness) is dangerous and abandoned. LC-MS/MS on viscera confirms aconitine (m/z 646 to 586) and mesaconitine (m/z 632 to 572).

Nerium oleander (kaner)and Thevetia peruviana / Cascabela thevetia (yellow oleander, pila kaner)both contain cardenolide glycosides (oleandrin in Nerium, thevetin A and B in Thevetia) that inhibit the Na+/K+-ATPase identically to digoxin. Inhibition raises intracellular sodium, which raises intracellular calcium through the Na+/Ca2+ exchanger, producing bradyarrhythmia and hyperkalaemia at toxic doses.

Indian epidemiology. Yellow oleander seeds are the leading suicidal plant poison in Sri Lanka (thousands of cases per year through the 1990s) and a major substance in Kerala, Tamil Nadu and coastal Karnataka. Two to ten seeds are often fatal. Treatment is digoxin-specific Fab fragments (Digibind), which cross-react with cardenolides.

Seed identification. Yellow oleander seeds are flat, triangular to wedge-shaped, 1.5 to 2 cm, with a hard pale-brown shell over a white oily kernel. Nerium seeds are smaller, narrow, hairy at one end.

Detection. The Keller-Kiliani test is the classical colour test for the 2-deoxysugar moiety of cardenolides: glacial acetic acid with a trace of FeCl3 layered with concentrated H2SO4 gives a reddish-brown ring at the interface and a blue-green upper layer.Kedde's reagent(3,5-dinitrobenzoic acid in alkali) gives pink-violet with the unsaturated lactone ring. Confirmation is by LC-MS/MS on serum and viscera.

Strychnine (Strychnos nux-vomica, kuchla). Disc-shaped grey seeds about 1.5 cm across, velvety on the surface with a deeply cordate hilum, are diagnostic on powder microscopy. Strychnine is a competitive glycine-receptor antagonist at the spinal cord; loss of inhibitory tone produces tetanic convulsions on the slightest stimulus, opisthotonus (arching of the back) and risus sardonicus (the spasm-fixed grin). Consciousness is retained. Death from exhaustion or asphyxia within an hour. The bichromate-sulphuric reaction is the classical colour test: strychnine on a slide treated with concentrated H2SO4 and a trace of potassium dichromate gives a violet colour that fades through red to yellow. Brucine in the same plant gives deep red with concentrated HNO3, turning orange on warming.

Cyanogenic glycosides. Amygdalin (bitter almonds, apricot kernels), linamarin (cassava, bamboo shoots), prunasin (cherry pits). On hydrolysis they release HCN, which inhibits cytochrome c oxidase. Detection at autopsy is by the sodium picrate paper test on stomach-content vapour (yellow paper turns brick red), with confirmatory microdiffusion in a Conway cell. Cassava-related tropical ataxic neuropathy is reported in India, primarily in Kerala and parts of Andhra Pradesh where tapioca is a dietary staple.

Capsaicin. The pungent principle ofCapsicumspecies. Used in self-defence sprays. Detected by HPLC with UV at 280 nm.

Opium-poppy alkaloids belong to the stimulants, narcotics and opiatesbullet.

The pipeline for a suspected plant poisoning starts with post-mortem and viscera collection in poisoningat the medical-college autopsy room, viscera receipt at the state SFSL or CFSL under BNSS Section 176, Stas-Otto acid-base fractionation, screening by TLC and colour tests, and GC-MS or LC-MS/MS confirmation. Plant material from the scene (seeds, tubers, paste) goes to the same lab for powder microscopy.

Five Indian casework contexts:

1. Datura highway-robbery cases in Madhya Pradesh, Uttar Pradesh, Rajasthan and Bihar from the 1980s onward. Charged under IPC Section 328 (now BNS Section 328).
2. Yellow-oleander (Thevetia) suicidal poisoning as a recurring rural Kerala and Tamil Nadu pattern, with hundreds of admissions to Thiruvananthapuram and Coimbatore tertiary-care hospitals each year.
3. Bachhnag (aconite) accidental poisoning from underprocessed Ayurvedic preparations and misidentified tubers in Himachal and Uttarakhand. Reported by IGMC Shimla and AIIMS Rishikesh poison-control units.
4. Historical abrus "sui" cases in which a sharpened needle of abrus paste was driven into the flank of a draught animal to kill it for the hide. Largely historical but fixed in Modi's Medical Jurisprudence and Toxicology.
5. Cassava-related konzo and tropical ataxic neuropathy in tribal Odisha and Andhra Pradesh, from inadequate processing of bitter cassava.

Institutional anchors: state SFSL toxicology divisions for routine viscera analysis, CFSL Hyderabad and CFSL Chandigarh for complex casework, AIIMS New Delhi for clinical-autopsy correlation, and NIN Hyderabad for plant-material identification. The animal and venomous poisonsbook chapter is the companion biological-category reference.