A coffee tree

Coffee tree – species Coffea L. 


C. arabica L. – Arabian coffee, lives in the wild in Ethiopia, in river valleys, at an altitude of 1600-2000 m above sea level. m., where real forest thickets (undergrowth) are still preserved in the province of Kaffa. It is cultivated in many tropical states, accounting for 90% of the world’s coffee plantations. Plants cannot stand the heat of the tropics below 1200-1500 m above sea level. m., therefore, in the lower zones it is replaced by heat-resistant C. canephora Pierre (C. robusta Linden). Precipitation in the cultivation zone should be at least 1300 mm per year; with a lack of moisture, artificial irrigation will be necessary.

C. canephora Pierre – Congolese coffee, typical of the equatorial forests and savannas of the Congo Basin. Crosses easily with C. arabica, very productive species. Widely cultivated in Indonesia.

C. liberica Hiern. – Liberian coffee. Grows wild in tropical West Africa. Cultivated from Senegal to East Africa, in Sri Lanka, Indonesia.

C. mokko hard. —mocha coffee (named after the port of export), Yemeni coffee, is a garden variety of C. arabica. Introduced into culture in Arabia.

Although the birthplace of the coffee tree is Africa, the most extensive plantations are found in Latin America, especially in Brazil. Smaller areas are occupied by coffee in Southeast Asia and Africa. Coffee occupies a larger area on a global scale than tea.

Shrub or small tree, 8-10 m tall, evergreen, trunk with greenish-gray bark. The branches are long, flexible, spreading or drooping. Leaves entire, slightly wavy, opposite, 5-20 cm long and 1.5-5 cm wide, on short petioles. The flowers are white, fragrant, 3-7 in the axils of the leaves, regular, 5-membered, cleaved. It blooms and bears fruit all year round. The fruit is a berry, almost spherical or oval, dark red, two-seeded, 1-1.5 cm in diameter.

The harvested ripe berries are subjected to “dry” or “wet” processing. During dry processing, the berries are dried in the sun and then the fruit, which is fragile within the limits, is removed by machines. With the wet method, fresh berries are passed through special machines and the pulp is washed off in a stream of water.

Seeds (Semen Coffea) are light gray, hard, oval-shaped, flat-convex, with a deep furrow on the flat side. The seeds are covered with a thin “silver” or “parchment” shell, which is erased during processing and its remains are retained only in the furrow.

The seeds contain from 0.7 to 2% caffeine, depending on the variety. Yemeni coffee is recognized as the best variety. Congolese coffee is most suitable for the production of instant coffee (Nescafe, Instant coffee). Liberian coffee contains relatively little caffeine (1.2-1.3%). There are many commercial varieties of coffee – “for different prices and different tastes.”

Coffee is used as a stimulant for mental fatigue, headaches and for first aid in case of poisoning. The effect of coffee on the nervous system was first noticed by the shepherds of Ethiopia, watching how goats and sheep, having eaten fallen fruits from wild coffee bushes, did not sleep at night.

The plant contains purine alkaloids.



Purine is a fused system of pyrimidine and imidazole rings. Purine alkaloids in nature are represented by methyl derivatives of the oxygen derivative of purine – xanthine (2, 6-dioxipurine). The main ones are caffeine, theobromine and theophylline.



Purine is a fused system of pyrimidine and imidazole rings. Purine alkaloids in nature are represented by methyl derivatives of the oxygen derivative of purine – xanthine (2, 6-dioxipurine). The main ones are caffeine, theobromine and theophylline.


Alkaloids are called natural nitrogen-containing compounds of the main character, formed in plants. Groups of proteinogenic amines (for example, tyramine) and betaines (stakhidrin, trigonelline, etc.) adjoin the alkaloids, which are considered as transitional compounds from the simplest nitrogen-containing compounds (methylamine, trimethylamines, etc.) to the alkaloids themselves.

Of natural pharmacologically active substances, alkaloids are the main group from which modern medicine draws the largest number of highly effective drugs.

According to world literature, by the end of the past decade, the number of alkaloids isolated from the higher plants of the Earth’s flora exceeded 5000. According to modern concepts, alkaloid-bearing plants make up 10% of the entire world flora. The families Equisetaceae, Lycopodiaceae, Ephedraceae, Liliaceae, Amaryllidaceae, Dioscoreaceae, Chenopodiaceae, Nymphaeaceae, Ranunculaceae, Berberidaceae, Menispermaceae, Papaveraceae, Fabaceae, Rutaceae, Cactaceae, Punicaceae contain the largest number of alkaloid-bearing genera and species. Loganiaceae, Apocynaceae, Borraginaceae, Solanaceae, Rubiaceae.

Usually, plants that are phylogenetically close contain alkaloids that are very similar in structure, thus forming a natural group of genera. For example, plants of the genera Atropa, Datura, Hyoscyamys, Scopolia, Physochlaina, Duboisia. Mandragora (all from the same Solananeae family) contain a well-defined group of tropane alkaloids. This far-reaching pattern, however, has exceptions that have not yet been explained. So, for example, caffeine is found in plants that are not systematically related to each other: tea (Theaceae), coffee (Rubiaceae), cocoa (Sterculiaceae), mate (Aquifoliaceae), guarana (Sapindaceae), erodium (Geraniaceae). Along with this, cases are known when of their 2 very systematically close species, one is rich in alkaloids, and the other either does not contain them at all, or contains alkaloids of a different structure.

Alkaloids can be found throughout the plant, or they can be formed and accumulated only in one or more specific organs. The plant traditionally contains not one, but several alkaloids. In individual plants, there may be 20 or more of them (cinchona, hypnotic poppy, etc.), and they may be similar in structure or belong to different chemical groups. In the sum of alkaloids, 1–3 traditionally predominate quantitatively (the main alkaloids). In plants, alkaloids are dissolved in the cell sap of the main parenchyma, phloem, and other tissues in the form of salts, mainly organic acids (malic, succinic, citric, oxalic, fumaric, quinic, etc.); of mineral acids, phosphoric acid is more often involved.

The quantitative content of alkaloids is, in principle, a species characteristic, and it varies over a very wide range. For example, in black henbane they are only 0.05-0.1%, and up to 15% accumulate in the cinchona bark. In the process of ontogenetic development of plants, their alkaloid content undergoes quantitative and sometimes qualitative changes, and each species has its own regularities.

The content of alkaloids in plants is influenced by their geographical location and various factors (air and soil temperature, precipitation, duration and intensity of sunlight, shading, height above sea level, etc.), as well as human impact in the case of transferring the plant to cultivation or its acclimatization. The largest number of alkaloid-bearing species, moreover, with a high content of alkaloids, is common in subtropical and tropical states with a humid climate. Alkaloids of different structure are confined to certain latitudes, and in connection with this, their pharmacological activity changes.

There is no consensus on the biological role and causes of the formation of alkaloids in plants. The main hypotheses proposed at different times interpret alkaloids as: 1) waste products of the vital activity of a plant organism; 2) spare substances; 3) protective substances; 4) active substances necessary for biosynthesis. The latter hypothesis is currently considered by most scientists to be the most general one, which, however, does not exclude other biological functions of alkaloids.

The exceptional diversity in the structure of alkaloid molecules does not allow us to imagine a single way of their formation in plants. Their biosynthesis proceeds according to specific schemes with the most complex chemical transformations (ring opening and closing, oxidation, deamination, ring condensation, etc.) through many intermediate products. Some alkaloids begin biogenesis from amino acids, others from acetic acid (in other words, from carbohydrates).

The modern classification of alkaloids is based on the nature of the heterocycles included in their molecules, with the release into a separate group of alkaloids with an aliphatic structure and with nitrogen in the side chain.

1. Alkaloids with an aliphatic structure or with nitrogen in the side chain;

2. Pyrrolizidine alkaloids.

3. Piperidine and pyridine alkaloids.

4. Alkaloids with condensed and pyrrolidone and piperidine rings.

5. Quinoline alkaloids.

6. Quinazoline alkaloids.

7. Isoquinoline alkaloids.

8. Indole alkaloids.

9. Alkaloid of the imidazole group.

10. Purine alkaloids.

11. Diterpene alkaloids.

12. Steroid alkaloids (glycoalkaloids).

13. Alkaloids of unknown structure.

In conclusion of this brief review, it should be pointed out that most alkaloids are highly active substances with selective pharmacological action. The selectivity of the action of alkaloids determines their widespread use for medicinal purposes. The main forms are extraction products (tinctures, extracts, novogalenic preparations, etc.) and pure alkaloids isolated from plants, converted into soluble salts of certain inorganic and organic acids.

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