The homeland of ipecac is Brazil, where it grows on a vast territory in the upper reaches of the right tributaries of the Amazon River. During the dry season, experienced pickers go out to harvest, as it is not easy to find this small plant in dark, humid, vast forests. The aerial part of ipecac traditionally does not exceed 30-40 cm and consists of a thin stem bearing several pairs of opposite evergreen broadly lanceolate leaves; a small inflorescence develops at the top – a head of crowded white small tubular flowers.
The fruit is a fleshy drupe. Under the ground stretches a gray-brown long thin horizontal rhizome with a smooth surface. In the nodes, long roots depart, which have a special structure; they are composed of hardwood and broad bark; the bark grows unevenly, with ring constrictions, which makes the root look like a rosary. Only these roots are used. Having cut them off, the pickers immediately bury the tops of the rhizome in the ground, it grows back and after 3-4 years the thicket is restored. Despite this, the need for ipecac is so great that industrial plantations have been established in India, Indonesia, and Tanganyika.
Raw materials should consist only of bead-like roots of a gray-brown color. Their smell is peculiar, musty; the taste is bitter-nauseous. Root diameter 4-5 mm, length 10-15 cm. Smooth pieces of rhizome impair raw materials, since their bark is thin, and alkaloids are found only in the bark. The bark of dry roots is very fragile and easily separated from the wood when crushed.
The root contains 2-2.5% (up to 4%) of the amount of alkaloids. The main one in terms of quantity and action is emetine, which is within 70% of the amount. Opened in 1817 by Pelletier, but only in 1879 was obtained in its pure form by V. Podvysotsky; the formula was established in 1948 by Robinson, and in 1950 N. A. Preobrazhensky confirmed the structure by synthesis.
The second largest alkaloid, cephalein, contains one CH 3 group less than emetine, and can serve for its semisynthesis. The remaining alkaloids are in trace amounts. In addition, it is within 2% of saponins and the glycoside ipecacquinine.
The root is used in infusion and cough powder as the best expectorant (0.02-0.05 g each); large doses (0.5 g or more) act as emetic; the product serves as a specific remedy against amoebic dysentery.
The plant contains isoquinoline alkaloids.
PLANTS CONTAINING ALKALOIDS
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.