Plants affecting the CNS
1 I. True alkaloids
Amino acid derivates which contain nitrogen in the heterocycle
2 I.1. Tropane alkaloids
Tropane rings are biosynthesised from ornithine amino acid Me = (-CH 3) Two major tropane alkaloid groups: • Solanaceous alkaloids • Coca alkaloids
Natural occurence in species of Solanaceae , Erythroxylaceae, Convolvulaceae Major alkaloids are: S and R atropine (S) (R) hyoscyamine (one of its hyoscyamine enantiomers is atropine ), scopolamine (syn: hyoscin), cocaine 3 scopolamine Determination of tropane alkaloids
Vitali – Morin colour reaction
1 g sample from the plant + 20 ml fuming H2SO4 solution Evaporated to dryness on a water-bath To the residue add 0,5 ml 3% (w/v) KOH in methanol bright purple colouration changes to red fades to colourless
4 Mechanism of action Inhibition of muscarinic cholinergic receptors (competitive antagonists of acetylcholine) Site of action : smooth and cardiac muscle, gland cells, in peripheral ganglia and CNS Alkaloids bounds reversible to receptors Solanaceous alkaloids are anticholinergic , reducing the activity of the parasympathetic nervous system and promoting sympathetic predominance Symptoms are developed in 30-60 minutes, lasts for 2 hours (intensive phase), later decrease for 10-12 hours (except in the eyes: 72 hours) Alkaloids are excreted with urine 5 Major symptoms 1. Xerostomia (dry mouth) 2. Mydriasis (dilated pupils) 3. Tachycardia (high heart rate) 4. Rapid breathing 5. Spasm, seizures 6. Death (respiratory failure)
6 Datura stramonium – jimsonweed Solanaceae – nightshade f. Distribution: Mexico, but naturalised in many countries Annual weed Disturbed, nutrient (nitrogen) rich fields, from early summer Used to „treat” roaring (respiratory obstruction) horses before selling them Psychoactive effects jimson weed (Jamestown, Virginia) Treatment for asthma
7 8 9 Seed is dominated by numerous pock-like depressions The surface of the seed is covered evenly with minute bumps Unmature seeds have a sweet taste! 10 Poisoning The whole plant is poisonous for all species ! Level of toxins vary among plant organs: ~ 0,2-0,6% Toxins accumulate in tissues! Generally seeds admixed into the meal It’s rarely grazed due to the bitter taste and unpleasant smell Most susceptible: pigs Less susceptible: rabbits , poultry
11 Case studies Schulman & Bolton (1998): high proportion of seed in the forage
Binev et al. (2006): ensiled maize with Datura plants
Soler-Rodríguez et al. (2006): lucerne hay with Datura
12 Naudé et al. (2004): hay samples contamined with Datura
13 Other Datura species
Datura innoxia – downy thorn-apple
14 Hyoscyamus niger – henbane Solanaceae – nightshade f. Distribution: continental Eurasia, India, N-Africa Annual/biennial weed On waste ground and also as a cereal weed Formerly used to steal chickens, applied at witch rituals, against toothache or in beers as a flavouring As a medicine: antispasmodic, bronchodilator effect
15 16 17 Seeds are compressed and scrobiculate (pitted): having numerous shallow grooves or depressions
18 Poisoning The whole plant is poisonous for all species ! Symptoms are similar to Datura poisoning Mainly humans are affected
19 Atropa belladonna – deadly nightshade Solanaceae – nightshade f. Distribution: Europe, N-Africa, W-Asia Perennial, herbaceous plant (often growing as a subshrub) In shady forests from early summer Atropos – one of the three Greek fates of destinies
Bella donna (in Italian) – beautiful lady Formerly it was used as a love potion Atropine sulphate is a mydriatic for eye examinations, antispasmodic effect 20 21 22 23 Seeds are ornamented by numerous pock-like depressions
24 Poisoning
The whole plant is poisonous for all species Symptoms are similar to Datura , but poisonings are rare Average toxin content (in the above-ground parts): 0,2-2% Tolerant species: rabbit, birds, guinea pigs Susceptible species: pigs LD: for kids 2-5 berries, for adults 10-20
25 Other European species with Datura-like symptoms Scopolia carniolica – European scopolia Mandragora officinarum - mandrake
26 Coca alkaloids Erythroxylum cocoa – coca shrub
with a stimulant effect
27 I.2. Benzylisoquinoline alkaloids
Natural occurences mainly in species of Papaveraceae family , but also species in
Aristolochiaceae and thyrosine isoquinoline Liliaceae Synthesis: isoquinoline backbone from thyrosine amino acid Most important alkaloids: morphine, codeine, papaverine, rhoedine Commercial drug tests available (Mandelin reagent)
28 Mechanism of action – opioids (morphine)
Opioids bound to an opioid receptor of a neurone Blocking Ca 2+ ions entering the cells K+ ion efflux Hyperpolarization inhibition of action potential neurons less likely to fire paralysing effect, suppression of transmission of pain signals 29 Symptoms – opioids (morphine)
Pinpoint pupils Spasm of the stomach or intestinal tract, vomiting Paralysis of limbs stumbling walk Slow and labored breathing Urinary retention, constipation Coma, hallucinations, death
30 Papaver rhoeas – field poppy Papaveraceae – poppy f. Distribution: cosmopolitan (worldwide) Agricultural weed (cereals); from spring Annual Pappa (in Latin) = food, milk Rhoeas (in Greek) = red Toxic agents are rhoeadine papaverine alkaloids (about 25 different molecules, the major type is rhoeadine – nearly 50% of the total) and papaverine 31 32 33 Small, kidney-shaped seeds with a dark, greyish brown colour
34 Poisoning
The whole plant is poisonous (especially its milk) for all species Can be admixed in hay and meals Poisonings are rare Toxins can be excreted in the milk a potential risk for offsprings Mainly cattle, horses and sheeps are sensitive Slow recovery after poisoning
35 Other Papaver species Papaver somniferum – opium poppy
Somniferum (in Latin) – „sleep bringing” Dried latex = opium The mixture of about 50 different alkaloids (morphine, codeine, papaverine, etc.) Painkilling effect János Kabay – extraction of morphine from poppy straw
36 37 I.3. Piperidine alkaloids Natural occurence in species of Apiaceae family Synthesis: piperidine nucleus biosynthesised from lysine amino acid (true alkaloid) or from acetate (pseudoalkaloid) Most important molecules: coniine , coniceine, lobeline Coniine + NaOH (KOH) unpleasant smell, similar to mice urine
38 Mechanism of action – coniine In the peripheral nervous system coniine blocks the nicotine receptors on the post-synaptic membrane of neuromuscular junctions blocking movements Depresses the cranial nerve III. depressing motor functions The central nervous system is not immediately affected
Sypmtoms Symptoms develop within 0,5-2 hours Uncontrolled urination Heart rate first slow, becomes rapid Trembling, problems in movement (paralysis of limbs) Respiration becomes slow, labored, and irregular Person remains conscious and aware until respiratory paralysis 39 Conium maculatum – hemlock Apiaceae – carrot f. Distribution: Europe Disturbed habitats, on nutrient (nitrogen) rich soils from summer Biennial Maculatum (in Latin) = spotted 8 different alkaloids, mainly coniine , coniceine Death of Socrates – infusion of hemlock plant
40 41 42 43 Fruit is dry but does not split open when ripe Ridged, compressed laterally and smooth
44 Poisoning The whole plant is poisonous , but mainly the green fruits (alkaloid content up to 2-3%) All species are susceptible, mainly cattle Can be admixed into hay, silage or meal Drying can decrease toxicity About 100-500 g green leaves can be lethal
45 Case studies
Gelay et al. (1992)
Binev et al. (2007) 46 II. Terpenoids
47 II.1. Diterpene pseudoalkaloids Natural occurence mainly in species of Ranunculaceae, Asteraceae, Euphorbiaceae, Lamiaceae families Biosynthesised from geranyl- geranyl pyrophosphate (GGPP )
kaurene (C20 ) with a nitrogenic atom pseudoalkaloid
(with C19 skeleton) Major types are aconitine and Taxus alkaloids No quick tests but determination of aconitine is possible from blood and urine see Beike et al.
(2004) 48 Mechanism of action - aconitine In the cardiac and skeletal muscle cell membranes, aconitine makes the voltage-gated Na + ion channels permanently open high Na + levels in muscle cells inhibits Na +/Ca 2+ exchangers higher Ca 2+ and Na + ion availability within the muscle cell cell membrane cannot be repolarized paralysis In neurons , aconitine depolarizes both the membranes of presynaptic and postsynaptic cells by opening their voltage- gated Na + ion channels Due to the strong depolarization, the permeability of the membrane for K+ and Ca 2+ ions is increased Ca 2+ ions stimulate the release of Ach into the synaptic gap 49 Symtomps of Aconitum poisoning
Paresthesia (sensation of burning) Tingling and numbness in the mouth, burning feeling in the rumen Vomiting Motoric weakness , slowing movements Heart and respiration steadily fail (asphyxia ) Ventricular arrhythmias, asystole, cardiac arrest , death
50 Aconitum lycoctonum – wolfsbane Ranunculaceae – buttercup f.
Distribution: Middle and North Europe Over 250 Aconitum species mainly in the northern hemisphere Perennial In mountanious forests or gardens from mid-summer Formerly used as an arrow poison Dermal absorption of the alkaloids (aconitine , mesaconitine, hypaconitine) is possible
LD 50 : 1 mg/bwkg (mice) 1-2 mg/bwkg (human) 51 52 53 Poisoning The whole plant is poisonous for all species , but mainly the tubers and the seeds (even it’s dried) Animal poisonings are rare Mainly on alpine grasslands or in gardens
54 Puschner et al. (2002) Species with similar poisonous effects see Seminar 8 Delphinium spp. – Aconitum napellus – cultivated larkspur species monkshood
55 II.2. Steroidal triterpenoid pseudoalkaloids For the biosynthesis of steroid skeleton see seminar 4. Steroidal skeleton bounds with heterocyclic rings pseudoalkaloids Natural occurences in members of Liliaceae and Solanaceae plant families About 153 compounds have already been isolated from ~30 species Detection of Solanum alkaloids : adding formaldehyde (CH2O) and sulfuric acid (H2SO4) the red-violet color indicates alkaloids No quick tests for Veratrum alkaloids 56 Mechanism of action and symptoms - Solanum alkaloids
Inhibition of acetylcholinesterase ACh accumulates Na + channels stay open no possibility of a new action potencial to be triggered no more muscle contractions paralysis Saponin effect : disrupts cell membranes Symptoms are similar to potato poisoning see seminar 3.
57 Solanum nigrum – black nightshade Solanaceae – nightshade f.
Distribution: Eurasia, but naturalised worldwide Annual Disturbed habitats, on soils rich in nutrient (nitrogen), crop fields, or in gardens from summer Agricultural weed Nigrum (in Latin) = black (berries) Solanine glycoalkaloid (aglycone: solanidine)
58 59 Poisoning The whole plant is poisonous for all species (especially for kids) Toxins are poorly absorbed from the gastrointestinal tract and eliminated rapidly by urinal and fecal excretion Most cases reporting mild toxicity following ingestion
LD50 : 30-40 mg/bwkg (mouse), 20 mg/bwkg (rabbit)
60 Solanum dulcamara – bittersweet nightshade Solanaceae – nightshade f.
Distribution: Eurasia, but naturalised worldwide In fresh forests, hedges and marshes from late autumn Dulcis (in Latin) = sweet, amara (in Latin) = bitter Solanine glycoalkaloid (aglycone: solanidine)
61 62 Misidentification – confused taxa Solanum dulcamara
Lycium spp. – goji berry, wolfberry
63 Other speices
Solanum pseudocapsicum – Jerusalem cherry
64 Case studies
Lima et al. (2014)
65 Mechanism of action and symptoms – Veratrum alkaloids
Jervine – inhibits smoothened (SMO) protein inhibition of hedgehog signaling pathway (controlls embryo developement) Protoveratrine - opens the Na + channels of neurones permanently For embryos: teratogenic and mutagenic effect birth defects For adults: symptoms are similar to Aconitum poisoning with hemorrhages
66 Veratrum album – white hellebore Melanthiaceae – death camas f. Distribution: Europe, W-Asia
On lush grasslands, from early cholesterol summer Perennial Album (in Latin) = white (flowers) Steroidal alkaloids (the basic steroidal skelet changes in many steps): protoveratrine, jervine, veratridine Supposed death of Alexander the Great Ethnoveterinary – against skin parasites 67 68 69 70 Poisoning
The whole plant is poisonous (mainly the rhizome) for all species Sheeps are susceptible Plants can be nibbled on pastures , or admixed in the hay Symptoms develop in 1-2 hours
LD50 : 0,1mg/bwkg (rabbit), 1-2 g rhizome/forage kg (ruminants)
71 72 Other Veratrum species Veratrum nigrum – black hellebore
73 Case study
Mainly bioassay experiments
74 II.3. Non-steroidal triterpenoids
Aglycons biosynthesised from squalene, but pentacyclic molecules squalene Many of them are glycosides forming an amphipathic molecule (=saponin) Distribution: non taxa specific compounds (origin: Saponaria species) For detailed mechanism and symptoms see seminar 3. (forage legumes)
75 Agrostemma githago – corncockle Caryophyllaceae – pink f. Distribution: in the continental region Weed of wheat; from summer Annual Toxic agents are triterpenoid saponins (aglycone: githagenin) and agrostin (RIP protein) In Europe now it’s only locally distributed increased use of agrostemma saponin herbicides 76 77 Angular-oval shape, often flattened on one side Covered in rows of raised tubercles (wart- like projections) that increase in height away from hilum
78 Poisoning
The whole plant is poisonous, but mainly the seeds (toxin content can reach 5-7%) Poisonous for all species Seeds can admixed into meals Symptoms are developed in 1-2 hours Acute poisoning: respiratory depression , vomiting, diarrhea, salivation and paralysis No recent studies about the LD value, but doses higher that 2-3 g seeds are considered toxic for humans 79 Case study
Less published data about poisonings
80 III. Thiaminase enzyme
81 Mechanism of action Enzymes cleave the thiamine (vitamin B1) molecule and render it biologically inactive When thiamine molecule is cleaved the body is incapable of restoring it thimanine deficiency (humans: beri-beri)
Vitamine B1 has a pivotal role in carbohydrate and fatty acid metabolism acting as a coenzyme in the pyruvate dehydrogenase enzyme complex that produces acetyl-CoA from pyruvate Low levels of acetyl-CoA can lead to metabolic coma and death Source of thiaminase: in fish, shellfish, ferns, bacteria Fish thiaminases are heat sensitive, but the fern-type may not be completely destroyed by cooking 82 Symptoms Weakness, decreased production, milk with bluish color Enlarged heart, low heart beat In ruminants: cerebrocortical necrosis (CCN) (polyencephomalacia PEM) – behavioral disorders Brain becomes inflamed and edematous
83 Equisetum arvense – field horsetail Equisetaceae – horsetail f. A fern plant Distribution: throughout the arctic and temperate regions An agriculture weed, on disturbed grasslands Perennial Brown (fertile) shoots appears in spring, green (steril) shoots in summer Rich in silicon dioxide (silica ) Used to treat urinary infections or to polish pewter
84 85 86 Poisoning Silica crystals can irritate the digestive tract Ruminants are fairly resistant to thiamine deficiency, but young animals can be sensitive LD: over 20% in the hay (horses) – symptoms develop in 2-5 weeks Diets rich in whole grains can trigger the growth of certain thiaminase-producing bacteria (Clostridium sporogenes, Bacillus spp.) in the rumen
87 Other Equisetum species
Equisetum palustre – marsh horsetail
88 Other species with thiaminase content
Pteridium aquilinum – bracken fern Marsilea drummondii - nardoo
89 Cyprinus carpio - carp Clupea harengus – atlantic herring
Mytilus galloprovincialis - mediterranean mussel Penaeus spp. - prawns
90