Aconite – Aconite ferox Wall., A. fischeri Reichb. (A. chinense Sieb.)
A. ferox – wild aconite, grows in the subalpine zone of the Himalayas at an altitude of 3000-4000 m above sea level. m. A. fischeri – Fisher’s aconite, typical of the flora of Vietnam, China, Japan; found on Sakhalin and Kamchatka.
Both species are perennial herbaceous plants, 1.5–1 m tall or more. The leaves are rounded, palmately dissected, the lower leaves are on long petioles, the upper ones are almost sessile. Inflorescence – loose brush of blue flowers. Flowers irregular, calyx 5-leafed, corolla-shaped, upper leaflet in the form of a low helmet. Under the helmet there is a reduced corolla, turned into two blue bent nectaries, with a short spur. There are many stamens. The fruit is a multi-seeded complex leaflet.
Among themselves, these species differ mainly in leaves, fruits and roots. The lower leaves of A. ferox are 5-digitally dissected, their lobes are pinnately dissected into narrow segments, the blade is large, up to 20 cm in diameter; fruit of 2-5 leaflets; tubers are oblong, turnip-swollen or almost cylindrical, dark brown outside. The lower leaves of A. fischeri are smaller, within 8 cm in diameter, 5, 7-finger-dissected, the lobes are wide, with large sharp teeth; pedicels of lower flowers curved; plate of nectaries widely swollen; leaflets 3; tubers are short-conical, light gray outside.
Tuber roots (Tuber Aconiti) are harvested. Pseudoaconitine is the main alkaloid in A. ferox. It is considered the most poisonous type of aconite. The amount of alkaloids in A. fischeri tubers can reach 3%; the main alkaloid is aconitine.
The skeleton of aconitine consists of 19 carbon atoms and has a lyoctonine structure. The lethal dose of aconitine is 3-6 mg.
Both species are often used in Indian and Oriental medicine as an anesthetic, for febrile diseases, externally for gout, rheumatism and sciatica.
The plant contains diterpene alkaloids.
PLANTS CONTAINING DITERPENE ALKALOIDS
Diterpene alkaloids selectively accumulate in plants belonging to the genera Aconite, Delphinium (Ranunculaceae), Erythrophleum (Fabaceae), Carrya (Cornaceae).
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.