[9.3] ALKALOIDS

• Qualitative identification: Murexide test (pink) 

• Pharmacologically important: derivatives of methylxanthines 

 PURINE BASES

Methylxanthines

• Potent bronchodilatory & stimulant molecules

• Inhibit PDE, resulting to an increase in cAMP, and NE release

Theophylline

• 1,3-dimethylxanthine

• Was widely used a bronchodilator in asthma

Theobromine

3,7-dimethylxanthine

Caffeine

• 1,3,7-trimethylxanthine

• Central stimulant, diuretic, and content of several carbonated beverages

• Alkaloid which does not react with, or form precipitate with alkaloidal reagents

• cola

• cofeea bean

• guarana

• mate

Caffeine-containing purine bases

Dried cotyledons of Cola nitida

COLA / KOLA NUTS 

• source

Caffeine (central stimulant)

COLA / KOLA NUTS 

• constituents

For manufacture of non-alcoholic beverages

COLA / KOLA NUTS 

• use

Coffea arabica

COFFEE BEAN

• source

• Caffeine 

  • Its aroma is due to caffeol 

  • Decaffeinized coffee has only up to 0.08% caffeine (more expensive, higher market price)

COFFEE BEAN

• constituents

paste from crushed seeds of Paullinia cupana

GUARANA

• source

• Caffeine + tannin 

  • Its caffeine content is twice as much as that found in coffee seeds

GUARANA

• constituents

• Stimulant

• Astringent

GUARANA

• use

leaves of Ilex paraguariensis

MATE / PARAGUAY TEA

• source

Caffeine + tannin

MATE / PARAGUAY TEA

• constituents

• Laxative

• Diaphoretic

• Diuretic

MATE / PARAGUAY TEA

• use

leaves of Camelia sinensis

Tea/ Thea

• source

• Caffeine

• Theobromine

• Theophylline

Tea/ Thea

• constituents

Theophylline: relief of asthma; reversible spasm in emphysema and bronchitis; narrow therapeutic index:

Tea/ Thea

• use

seeds of Theobroma cacao

Theobromine

• source

• Little CNS stimulation, preferred over caffeine in treatment of cardiac edema and angina

Theobromine

• notes

• diuretic, smooth muscle relaxant;

• suppository base

Theobromine

• use

• From phenylalanine and tyramine

• Represented by galantamine

Amaryllidaceae Alkaloids

caucasian snowdrop

Amaryllidaceae Alkaloids

• examples

Galanthus woronowii

CAUCASIAN SNOWDROP

• source

Galantamine

CAUCASIAN SNOWDROP

• constituents

• Cholinesterase inhibitor 

  • Extensively used in 1950s as curare reversal agent 

  • Modulator of nicotinic cholinergic receptors- augmenting central cholinergic neurotransmission

CAUCASIAN SNOWDROP

• use

monkshood

Terpenoidal Alkaloids

• example

Aconitum napellus

MONKSHOOD

• source

Ranunculaceae

MONKSHOOD

• family

Aconitine

MONKSHOOD

• constituents

• Aconitine can induce cholinergic excess (nausea, diarrhea, hypotension, etc.)

• Arrow poisons

• Formerly used as antineuralgic liniment 

• Cardiotonic properties due to higenamine

  • Active at about the same dosage levels as Digitalis glycosides

MONKSHOOD

• use