The coniferous (ephedra) family on the globe is represented by one genus, numbering within 30 species. In the USSR, 12 species grow; the main industrial species is horsetail ephedra, Ephedra equisetina Bunge, collected in many mountainous regions of Kazakhstan and the Central Asian republics.
In China and the states of Indochina, industrial species are dark ephedra – E. sinica Stapf, and horsetail ephedra.
In India and other states of Hindustan, industrial species are medium ephedra – Ephedra intermedia Schrenk, Gerard’s ephedra – Ephedra gerardina Wall, and ephedra nebrodensis – E. nebrodensis Tineo. The first two species are also typical of the flora of Central Asia.
The species composition of ephedra growing in the states of the Arabian Peninsula and Southwest Asia is close to the species of Central Asia and Hindustan.
In American species of ephedra (with the exception of Andean ephedra – E. andina Popp.) alkaloids were not found.
In Egypt, dark ephedra is bred for industrial purposes, in the USA, besides it, Gerard’s ephedra; in Australia, Indian species have been tested in culture.
All types of ephedra are shrubs or small trees; typical xerophytes. They grow in semi-desert and desert zones, in mountainous places along gravelly slopes, rising to 1300-1800 m above sea level. m., often form large thickets. Plants with dioecious flowers, dioecious, with jointed branches, leaves are reduced to scaly sheaths. Flowers in spikelets. The fruit is a fleshy yellowish or false berry.
The raw material is grass (Herba Ephedrae) which is harvested in early spring or autumn. The raw material is non-lignified apical parts of the plant up to 25 cm long, consisting of herbaceous jointed branches. The internodes in the fracture are woody. The raw material is light green in color, odorless, the taste is not tested (poisonous!).
Ephedra grass contains alkaloids – derivatives of -amino-phenylpropane; L-ephedrine, D-pseudoephedrine (optical isomer of ephedrine), L-norephedrine, LN-methylephedrine.
The content of the sum of alkaloids, and the main alkaloid – ephedrine varies depending on the type of ephedra and the places and conditions of growth. In the main industrial species E. sinica and E. equisetina, the amount of alkaloids can reach 3%, and ephedrine prevails in it, which is especially valuable; call, E. gerardina contains less alkaloids (0.3-1.9%) than the previous species, but the total proportion of ephedrine is high (up to 67%).
Ephedrine is obtained as hydrochloride (Ephedrini hydrochloridum); It is used in the treatment of allergic diseases (bronchial asthma, vasomotor rhinitis, urticaria, etc.), as well as a stimulant of the central nervous system and in case of poisoning with morphine, scopolamine and gangliolytics.
The plant contains alkaloids with an aliphatic structure or with nitrogen in the side chain.
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, there are cases when their 2 very close systematically 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.