24 - Dangerous plants

Question 1

Classification of Toxins
(xenobiotics)

Answer 1

1. Alkaloids
2. Glycosides
3. Terpenes and resins
4. Proteins, peptides and lectins
5. Phenols

Question 2

Alkaloid xenobiotics

Answer 2

Most common and potent
* Nitrogen containing bases
* E.g. Ephedrine

Question 3

Glycoside xenobiotics

Answer 3

Hydrolysis yields carbohydrate
* E.g. Salicin

Question 4

Terpenes & Resins

Answer 4

Isoprene unit(s), C5H8, with various side groups
* E.g. Hyperforin

Question 5

Proteins, Peptides, Lectin xenobiotics

Answer 5

Amino Acid chains, glycoproteins
* E.g. Ricin

Question 6

Ricin chains

Answer 6

A-chain: removes adenine residue from ribosome

B-chain: lectin

Question 7

Ricinus communis MOA

Answer 7

B-Chain binds cell surface glycolipids/proteins ➔ ENDOcytosis then to Golgi, ER

A-Chain binds rRNA in ribosomal subunit ➔ inhibit protein synthesis

Question 8

Phenol xenobiotics

Answer 8

Contain phenyl ring + OH
* E.g. capsaicin

Question 9

Capsaicin

Answer 9

Long aliphatic chain
* Embeds in cells of mucus
* Binds TRPV1 r
* Activation of pain fibres ➔ autoinflamm.

Question 10

Strychnos genus

Answer 10

Numerous indolomonoterpenic alkaloids
* Strychnine – Tetanizing toxin
* Curare - Curarizing toxin

Question 11

Strychnine

Answer 11

Spinal C convulsant
* POST-syn Glycine R antagonist
* Excitation
* SPASM after slight stimuli

Question 12

Curare

Answer 12

Competitive NACh R antagonist
* Definite order of muscle involvement ➔ death by respiratory failure

Question 13

Deadly Nightshade

Answer 13

Include
1. Belladonna alkaloids (e.g. atropine - anticholinergic)
2. Solanine, Chaconine (→ Hallucinations, GI, coma)

Question 14

Monks Hood (Aconite)

Answer 14

Alkaloid toxin blocks Na+ channels
* Prolonged stim. prevents closing

Question 15

Solanine

Answer 15

Potatoes
* Green ➔↑chlorophyll ➔ ↑ solanine
* Exact mechanism unknown
* Death unlikely

Question 16

Oleander Nerium oleander

Answer 16

Saponin-glycosides. 2-4 seeds lethal
* Saponin (steroid) group
* Glycoside (carbohydrate)
* Cardioactive

Question 17

Foxglove Digitalis purpurea

Answer 17

Has DIGItoxin
* Cardioactive steroid / glycoside
* Good oral absorption

Question 18

Both Digoxin and Digitoxin…

Answer 18

1. Inhibit Na+, K+ – ATPase on cardiac myocytes
2. ↑ intracellular Na+ and Ca2+
3. Activate Na+/Ca2+ exchanger
4. ↑ Ca2+ stim sarcoplasmic reticulum & ↑ mm contraction

Question 19

Hemlock Conium maculatum

Answer 19

Coniine - Nicotinic antagonist
* Flaccid and respiratory paralysis
* Rhabdo and ATN

Question 20

Asthma Causing Species

Answer 20

1. Pollen
2. Pelitory

Question 21

Aboriginal Medicinal Plants

Answer 21

1. Snake vine (anti inflamm)
2. Sandpaper fig + stinking passion flower (anesthetic)
3. Kangaroo apple (steroidal anti inflamm)
4. Goats foot (anesthetic)

Question 22

Hop Bush (Dodonaea viscosa)

Answer 22

Steroids, terpenoids but no alkaloids or proteins
* used for toothache and stonefish sting

Question 23

Tutin

Answer 23

Toxin from tutu plant (NZ)
* Incorporated into honey
* Glycine R Antag.

Question 24

Mad honey

Answer 24

Grayanotoxins
* Bind to voltage gated Na+ channels preventing inactivation
* Changes in consciousness

Question 25

Death caps

Answer 25

Several **Amanita** species known to contain *cyclopeptides* inc. ***amatoxins*** (**α-Amanitin**)

Question 26

The α-Amanitin cyclopeptide

Answer 26

**Uptake** via *sodium* taurocholate co-transporter polypeptide (OATP family) on **hepatocyte** sinusoidal membrane * Binds **RNA** polymerase **II** ➔ ↓ DNA ***transcription*** * Cell *death* ➔ **liver** failure

Question 27

Poisoning: 4 clinical phases

Answer 27

Phase **I** *asymptomatic* (up to 24hr) Phase **II** watery **diarrhoea**, abdominal **pain** Phase **III** *temporary* **resolution** Phase **IV** ***hepatic*** and ***renal*** failure (days later) ***Death*** within **7–10d**