Purine Alkaloids

Purine alkaloids are unique alkaloids with a nitrogen containing ring structure similar to that of purines. Purine and pyrimidine nucleotides, which are derivatives of xanthines, constitute the major structural units of purine alkaloids. They play an important role in pharmacology and food chemistry. Studies have shown that the characteristic identification reaction of purine alkaloids is the murexide reaction. Purine nuclei-containing alkaloids are oxygenated in the presence of strong acids (e.g., nitric acid) and hydrolyze to dialuric acid, which is partially reduced to alloxane and to 5-aminobarbituric acid. Both compounds form an insoluble reaction product: alloxanthine, which, in the presence of ammonia forms murexide-ammonium salts of purpuric acid-which is characterized by a purple-red color.

Figure 1. The basic structure of the purine nucleus in purine alkaloids.

Common purine alkaloids

Caffeine (1,3,7-trimethylxanthine), theobromine (3,7-dimethylxanthine), and theophylline (1,3-dimethylxanthine) are the three most widespread alkaloids belonging to this group. They are all methyl derivatives of xanthine and they commonly co-occur in a particular plant. These three classes of purine alkaloids are often refined into coffee, cocoa, cola, and tea and play an important role in pharmacology and food chemistry. They competitively inhibit phosphodiesterase, resulting in an increase in cyclic adenosine monophosphate and subsequent release of adrenaline. This leads to a stimulation of the central nervous system, a relaxation of bronchial smooth muscle, and induction of diuresis, as major effects. These effects vary in the three alkaloids. Caffeine stimulates the central nervous system and has a weak diuretic action, whereas theobromine acts in the reverse way. Theophylline has generally similar properties to the above, with a shorter, though more powerful diuretic action than caffeine; it relaxes involuntary muscles more effectively than either caffeine or theobromine.

Figure 2. Structural chemical formulas of common purine alkaloids.

Sources of purine alkaloids

Most purine alkaloids are derived from plants, especially dicotyledonous species distributed in tropical and subtropical climates. Coffee, tea and cocoa are the world's top three beverage plants, all of which are rich in purine alkaloids.

Coffee

Coffee consists of the dried ripe seed of Coffea arabica, C. canephora, C. liberica, or other Coffea species (Rubiaceae). The plants are small evergreen trees, widely cultivated in various parts of the world, e.g., Brazil and other South American countries, and Kenya. Coffee is one of the most popular drinks in the world, and it can be prepared and presented in a variety of ways. Coffee seeds contain 10–20 g/kg caffeine and trace amount of theophylline and theobromine.

Tea

Tea is the prepared leaves and leaf buds of Camellia sinensis, an evergreen shrub cultivated in China, India, Japan, and Sri Lanka. Some studies have shown that tea contains 1-4% caffeine, and small amounts (up to 0.05%) of theophylline and theobromine.

Cocoa

Cocoa is derived from the roasted seeds of Theobroma cacao (Sterculiaceae), a tree widely cultivated in South America and West Africa. Cocoa is the basis of the sweet food preparation chocolate. Cocoa contains 1-4% theobromine, and 0.2-0.5% caffeine.

What we offer

As a supplier of alkaloids, Alfa Chemistry has always shown great interest in the latest developments in purine alkaloids. Alfa Chemistry is committed to providing a wide range of purine alkaloids. If you do not find what you need, please contact us. We also offer product customization according to customer's detailed requirements.