Tag (Herbal medicines) Flashcards
Terpenes
Terpenes are the primary constituents of essential oils. the basic structure is derived from 5 carbon isoprene units linked together head-to-tail to form linear rings.
Most terpenes are chiral and the 2 enantiomers have different taste and smell
3 classes:
- Menthon (has =O on meta position)
- Menthol (has OH on meta position)
- Carvon (has =O on ortho position)
(The active groups on the ring are ketones and alcohols).
They are classified on basis of length of carbon chains:
- 5 carbons = hemi-terpenes
- 10 carbons = mono-terpenes
- 15 carbons = sesqui-terpines
- 20 carbons = di-terpenes
- 30 carbons = tri-terpenes
Largest class of secondary metabolites.
Many have a pleasant smell.
Most are volatile and insoluble in water.
Paclitaxel
- Drug to treat ovarian, breast, lung, pancreatic cancers
- Taxane- which is a family of diterpenes
- Interferes with microtubules during cell division
- Diterpene
Catharidine
- Terpenoid- a large and diverse class of naturally occurring compounds derived from five carbon isoprene units
- Retrieved from blister beetles and Spanish fly
- Very toxic to humans and if left on will cause blisters (and can cause priapism- long painful erection)
- Skin irritant nerve poison (lethal dose is 0.5mg/kg)
Natural products as poisons
Different patients can tolerate different amounts of a poison.
The content of natural products in plants and animals can differ depending on where they grow.
The water content can make an important difference when determining the concentration of the natural product.
Lipophilic compounds can get accumulated in the food chain.
Alkaloids
Alkaloids are a group of natural compounds that are nitrogen containing that react as bases and have physiological effect.
They are categorised according to their heterocycle (heterocyclic- a ring composed of atoms of more than one kind).
Many are chiral.
Most have trivial names relating to their occurrence or effect.
Like alkali metals (sodium, potassium, etc) many form white salts with hydrochloric acid.
Alkaloids occur in plants often as salts of organic acids or as glycosides.
Categorising alkaloids
Classified according to their heterocycle.
- Piperidine (N-H (N off the 6C ring))
- Pyridine (N (in 6C ring))
- Indole (N-H (N off the 5C ring))
- Quinoline (2 6C rings, N in para position in one)
- Isoquinoline (2 6C rings, N in meta position in one)
Piperidine alkaloids
Piperine and piperidine are the two major alkaloids extracted from black pepper
Piperine:
- Main alkaloid of black pepper
- Used for spicing up brandy and as an insecticide
- In the stomach it reacts with acid to produce an organic salt. the formaldehyde
Nicotine
- Strong nerve poison
- Stimulation of the nicotinic acetylcholine receptors
- Stimulation of the CNS, constriction of blood vessels (higher BP)
- Release of adrenaline, dopamine, serotonin
- Fatal dose is 1mg/kg
- Used in nicotine patches or sprays
Cocaine
- Main alkaloid of a coca plant in South America
- Used to be used as a local anaesthetic
- Used to be used in Coca Cola drinks
- Performance enhancing
- Highly addictive
Indole alkaloids
Tryptophan
- An amino acid
- Serves as a precursor for the synthesis of serotonin and melatonin
- Used by the liver to make vitamin B3 which is needed for energy metabolism and DNA production
Tryptamines
- Naturally occurring alkaloid
- Examples- melatonin, serotonin, DMT, and ‘magic mushroms’
- Can be potent hallucinogens
- Made by plants and animals from the amino acid tryptophan
Serotonin
- Neurotransmitter
- Cannot pass the BBB
- Regulates sleep (as it is a precursor of melatonin), mood, and appetite
- Connected to depression, sex drive, and circadian rhythm
Melatonin
- Secreted by the pineal gland in mammals
- Formation is inhibited by light
- Higher concentration at night
- Winter depression- incomplete inhibition of formation due to lack of sunlight
- Biosynthesised from serotonin
Purines
They show all the characteristics of alkaloids but do not react as bases.
Purin bases- adenine, guanine.
N-Methylxanthines- Theobromine, Theophylline, and 1,3,7-Trimethylxanthine (Caffeine).
- All 3 have a psychological (stimulating) effect on us (like alkaloids)
- Increase diuresis (habituation effect) and the secretion of bile
(Habituation effect- a behavioural response (decrease in quality) that results from repeated stimulation and that does not involve sensory adaption/sensory fatigue or motor fatigue)
Theobromine
- Found in cocoa beans
- Used as a vasodilator, diuretic, heart stimulant
- Toxic to dogs (chocolate)
Theophylline
- Found in tea leaves
- Used to treat COPD and asthma
Caffeine
- Found in coffee beans
- Stimulates the CNS and heart
- Increases blood pressure
- Stimulation of gut motility (careful in patient with diarrhoea, tannins in tea act as a thickening agent so do the opposite)
- Lethal dose is about 10g (100 cups of coffee)
