Classes of Natural Compounds - Terpenes, Alkaloids, Purines

What are terpenes?

• primary constituents of essential oils

• many have a pleasant smell

• most are volatile and insoluble in water

What is the basic structure of terpenes?

• derived from five-carbon isoprene units linked together in a head-tail to form linear chains or rings

How are terpenes classified?

• on the basis of the length of the carbon chain

How many carbons does Hemi-terpenes have and give an example?

• 5 carbons

• isoprene

How many carbons does Mono-terpenes have and give an example?

• 10 carbons

• Menthol - flavours, food additives

How many carbons does Sesqui-terpenes have and give an example?

• 15 carbons

• Arte-misinin - antimalarial drug

How many carbons does Di-terpenes have and give an example?

• 20 carbons

• Paclitaxel - antitumor agent, plant hormones

How many carbons does Tri-terpenes have and give an example?

• 30 carbons

• Lanosterol - precursor of steroid

What is paclitaxel used for?

• drug to treat ovarian, breast, lung and pancreatic cancers

• interferes with microtubules during cell division

What are most terpenes?

• chiral

What are the two chiral forms of limonene?

• one smells like lemon

• one smells like orange

What are the two chiral forms of asparagin?

• one it bitter

• one is sweet

What is cantharidine?

• a terpenoid

• retrieved from blister beetles and Spanish fly

• it is a skin irritant nerve poison

What is the lethal dose of cantharidine and what is the toxic effect of it?

• lethal dose 0.5mg/kg - minimum 32-56mg

• first toxic effect - leads to priapism (painful erection)

How does the content of natural products in plants/animals differ?

• can differ depending on where they grow

How does the water content make a difference of a natural product?

• water content can make an important difference when determining the concentration of the natural products

What type of compounds get accumulated in the food chain

• lipophilic compounds

What are alkaloids?

• group of natural compounds

• nitrogen containing chemical compounds that react basic and have a physiological effect

How are alkaloids categorised?

• according to their heterocycle

• over 20,000 examples

• many are chiral

How do most alkaloids act like?

• act like sodium and form white salts with hydrochloric acid

How do alkaloids occur in plants?

• as salts of organic acids or as glycosides

• both improve solubility of compound

Give some examples of alkaloids?

• piperidine

• indole

• quinoline

• isoquinoline

• tropane

What is piperidine alkaloid?

• main alkaloid of black pepper

• used for spicing up brandy, and as an insecticide

What is nicotine?

• strong nerve poison

• stimulates nicotinic acetylcholine receptors

• releases adrenaline, dopamine and serotonin

• stimulates CNS and constriction of blood vessels

• fatal dose - 1mg/kg

What is cocaine?

• main alkaloid of coca plant

• earlier widely used as local anastatic - benzocaine and lidocaine

• performance enhancing - highly addicitve

What is tryptamine?

• indole alkaloid

• made by plants and animals from amino acid tryptophan

Give two examples of tyrptamines?

• serotonin

• melatonin

What is serotonin?

• neurotransmitter - can’t pass BBB

• regulates sleep, mood and appetite

• connected to depression, sex drive and cardician rhythm

What is melatonin?

• secreted by pineal gland in mammals

• formation is inhibited by light

• higher concentration at night

• treatment of insomnia and jet lag

• biosynthesised from serotonin

What is winter depression?

• uncomplete inhibition of formation due to lack of sunshine

Are purines alkaloids?

• they show all characteristics of alkaloids but don’t react basic

Give two examples of purines?

• adenine

• guanine

What effect does N-methylxanthines have?

• increase diuresis and secretion of bile

What is the therapeutic use of theobromine?

• vasodilator

• diuretic

• heart stimulant

• produced in Ivory coast, Indonesia and Ghana

What is theophyline?

• found in tea leaves

• used to treat COPD and asthma

• produced in Chins, India, Kenya

How much caffeine is there in tea, coffee and cola nuts?

• Tea - up to 5%

• Coffee - 1.1.5%

• Cola nuts - 2%

What does caffeine do?

• stimulates CNS and heart

• increase blood pressure

• stimulates gut motility

What is uric acid?

• discovered in bladder stones

• final product of nitrogen metabolism in reptiles and birds

What leads to gout?

• sodium urate crystals in joints

What are the causes for gout?

• inborn kidney disfunction

• disrupted purine metabolism

• consuming too much meat