3. Purine bases

Question 1

What are purine bases?

Answer 1

Purine bases are derivatives of heterocyclic compounds that contain 6- membered pyridine ring and 5- membered imidazole ring.

Question 2

Where do purines occur?

Answer 2

It does not occur naturally but its derivatives are biologically significant. The pharmaceutically active purine bases are all methylated derivates of 2,6- dioxypurine (xanthine) derivatives.

Question 3

What are the 3 main purine bases?

Answer 3

Caffeine (1,3,7-trimethyxanthine), theophylline (1,3-dimethylxanthines) and theobromine (3.7-dimethyxanthine)

Question 4

What are the actions of purine bases?

Answer 4

They inhibit phosphodiesterases and increase the conc. of cAMP and cause the release of norepinephrine. They have significant actions: they cause relaxation of bronchi and smooth muscles, they active gastric secretions, stimulate the CNS, inhibit uterine contractions, induction of diuresis and have a weak chronotropic and ionotropic effect on heart.

Question 5

What are the various forms of coffee?

Answer 5

Coffee occurs as coffee bean or seed, roasted beans and decaffeinated coffee

Question 6

What is coffee bean?

Answer 6

Coffee bean is the dried, ripe seed of Coffea arabica Lirine or C. Liherica Hiern (fam. Rubiaceae), deprived of the most of the seed coat.

Question 7

What are the action of caffeine?

Answer 7

Coffee produces its actions via caffeine mostly. But chlorogenic acid and caffeol also produce actions and some of the unpleasant action of coffee are contributed to them.

Question 7

What is the composition of coffee seeds?

Answer 7

1-2% caffeine
0.25% trigonalline
3-5% tannins
15% glucose and dextrin
10-13% fatty acid oil composed chiefly of olein and palmatin
10-13% proteins

Question 7

What is the dose of caffeine in coffee?

Answer 7

100-150 mg

Question 7

Caffeine in instant coffee?

Answer 7

85-100 mg

Question 8

Caffeine in cocoa

Answer 8

5-40 mg

Question 9

Caffeine in cola

Answer 9

40-60 mg/12 oz

Question 10

Caffeine in tea?

Answer 10

60-75 mg

Question 11

Maximum estimated dose of caffeine daily?

Answer 11

1.5 g

Question 12

From where is caffeine obtained?

Answer 12

Caffeine is prepared from tea, tea sweepings, coffee roasters and tea dust.

Question 13

What are the characteristics of caffeine?

Answer 13

Caffeine is anhydroous or may contain a molecule of water. It is a dried powder mass or white needles matted together in a fleecy mass. It has a bitter taste and sublimes directly when heated instead of decomposing.

Question 15

What is the solubility characteristic of caffeine?

Answer 15

The solubility of caffeine in water is markedly increased by the presence of citric acid, benzoates, salicylates, and bromides; medicinal compounds of this class are citrated caffeine and caffeine and sodium benzoate.

Question 16

What is the use of sodium benzoate?

Answer 16

The latter is most suitable for intramuscular injection as an analeptic in the treatment of poisoning, as a stimulant in acute circulatory failure, and as diuertic.

Question 17

Give the dosage of caffeine?

Answer 17

Caffeine and its related compounds are central nervous system
stimulants. The usual dose of caffeine is 200 mg; of citrated caffeine, 300 mg; of caffeine and sodium benzoate injection, parenterally, 500 mg.

Question 18

What is Theobromine?

Answer 18

Theobromine or 3,7-dimethyixanthine is a compound prepared from the dried, ripe seed of Theobroma cacao or is made synthetically

Question 19

What are the characteristics of theobromine?

Answer 19

It occurs as a white, crystalline powder with a bitter taste and sublimes at about 260 C

Question 20

What are the solubility characteristics of theobromine?

Answer 20

The base is slightly soluble in cold water or in alcohol but is readily soluble when mixed with salts that form basic solutions, such as calcium salicylate, sodium acetate, or sodium salicylate.

Question 21

What is the use of theobromine?

Answer 21

Theobromine is a diuretic and a smooth muscle relaxant. It has
little stimulant action on the central nervous system and hence is preferred over caffeine in treatment of cardiac edema and of angina pectoris.

Question 22

What is the usual dose of theobromine?

Answer 22

The usual dose is 200 mg,3 times daily.

Question 23

What is tea?

Answer 23

Thea or tea consists of the prepared leaves and leaf buds of Camellia sinensis, a shrub or tree with alternate, evergreen leaves. The tea tree is indigenous to eastern Asia and is now extensively cultivated in China, Japan, India, and Indonesia.

Question 24

What is green tea?

Answer 24

Green tea is prepared in China and Japan by rapidly drying the freshly picked leaves in copper pans over a mild artificial heat. The leaves are often rolled in the palm of the hand as they dry.

Question 25

What is black tea?

Answer 25

Black tea is prepared in Sri Lanka and India by heaping the fresh leaves until fermentation has begun. They are then rapidly dried artificially with heat. Tea occurs as more or less crumpled, bright green or blackish green masses. Its odor is agreeable and aromatic; its taste is pleasantly astringent and bitter.

Question 26

What are the constituents of tea?

Answer 26

Tea contains 1 to 4% of caffeine and small amounts of adenine, theobromine, theophylline, and xanthine; about l5% of gallotannic acid; and about 0.75% a yellow volatile oil that is solid at ordinary temperatures and has a strongly aromatic odor and taste.

Question 27

What is theophylline?

Answer 27

Theophylline or 1,3-dimethylxanthines is isomeric with theobromine and was first isolated from tea in 1885. It is prepared synthetically from caffeine or by other means.

Question 28

What are the constituents of theophylline?

Answer 28

Theophylline occurs as a white, odorless, bitter crystalline powder that is soluble in about 120 parts of water.

Question 29

Define solubility characteristics of theophylline.

Answer 29

It is rendered more soluble when combined with basic compounds. Aminophylline or theophylline ethylenediamine, theophylline monoethanolamine, and theophylline sodium glycinate are commonly employed in medicine.

Question 30

What are the uses of theophylline?

Answer 30

Theophylline and related compounds are utilized principally as smooth muscle relaxants for the symptomatic relief or prevention of bronchial asthma and for the treatment of reversible bronchospasrn associated with chronic bronchitis and emphysema. In addition, theophylline possesses diuretic properties.

Question 31

What is the dose of theophylline used?

Answer 31

The usual dose of theophylline is, orally, the equivalent of 2.4 mg of anhydrous theophylline per kg of body weight every 6 hours initially, adjusted as necessary to control symptoms with a usual optimal dosage of 4.8 mg per kg of body weight every 6 hours.

Question 32

What is the dose of aminophylline used?

Answer 32

The usual dose of aminophylline is, orally, 3 mg per kg of body weight every 6 hours adjusted as necessary to an optimal dosage of 6 mg per kg every 6 hours and, intravenously, 250 to 500 mg every 6 hours.

Question 33

What is the use of aminophylline?

Answer 33

Aminophylline is also a valuable diuretic. It exhibits dilating action on the pulmonary vessels in relieving asthma and can lower venous pressure in certain cases of heart failure