clove Tree — Caiyophyllus aromaticus L.;
The homeland of the clove tree is the Moluccas and other islands of Southeast Asia, but it is also bred in other tropical states: on the islands off the eastern coast of Africa (Zanzibar, etc.), the Antilles (Jamaica, etc.), in Brazil, etc.
Evergreen tree 10-12 m tall with a pyramidal top, giving a dense shade. The leaves are opposite, broadly lanceolate, entire, dark green, leathery and shiny. In transmitted light, bright points (essential oil receptacles) are visible. The inflorescences are apical in the form of complex semi-umbels. The flowers consist of a bright red cylindrical receptacle (hypanthium), bearing 4 small red sepals at the top, and a pale pink 4-petaled corolla, falling off when blooming in the form of a hemispherical cap.
Carnation flowers – Flores Caryophylli. Collect unblown flower buds; their red color becomes dark brown when dried. The shape of clove buds resembles a nail (whence its name), 1-1.5 cm long. The smell is strong, fragrant; pungent, spicy taste. On a longitudinal section of a carnation under a magnifying glass, numerous large round receptacles with essential oil are visible, located along the periphery and especially densely at the base of the cylindrical receptacle. A benign clove in a glass of water floats upright with its head up, since the essential oil is heavier than water. A clove with a low essential oil content floats horizontally.
Cloves contain 17-20% essential oil (Oleum Caryophylli) and within 2% tannins. The essential oil is distilled off with steam under pressure. The oil is light in color when fresh, but gradually acquires a purple-brown color when exposed to air and light. Contains 70-85% eugenol, acetyl-eugenol (within 3%) and caryophyllene – a mixture of bicyclic sesquiterpenes. Eugenol is obtained from oil by solvent extraction or charcoal sorption.
Carnation flowers, like all spices, promote digestion and are used mixed with other spices in powder or alcohol tincture. Cloves are more important for the food industry than for medicine. For medicinal purposes, essential oil is used – in dental practice as an antiseptic. For these purposes, pure eugenol is used.
As a spice and medicine, cloves have been known since ancient times and enjoyed special attention in India, the Middle East, Egypt, China, they were even brought to Rome. The mummies of the ancient Egyptians were adorned with a carnation necklace; in China, etiquette prescribed that one should address the emperor with a speech only after chewing a clove. The first detailed description of the plant was made by the companion of Magellan, the Italian Pigatetta. The Portuguese, having taken possession of the Moluccan foundations, for the purpose of monopoly, limited the cultivation of the clove tree on their islands, while predatory exterminating it in all other places. The Dutch who replaced the Portuguese colonizers followed the same policy. However, in the XVIII century. the French managed with great difficulty to bypass the vigilance of the Dutch authorities and take out a whole ship of carnation seedlings,
Carnation fruits – Fructus Caryophylli. In addition to carnation buds, Anthophylli carnation fruits are also commercially available and are harvested almost ripe. The fruit is a false berry formed from the lower ovary enclosed in the receptacle. They are larger than buds – 2.5 cm long, of the same dark brown color. The shape of the fruit is oval, topped with the remaining 4 sepals, contains one seed rich in starch. Fruit powder can be distinguished from bud powder by the presence of starch. The smell and spicy taste of clove fruits are the same as those of the buds, even more pleasant. The essential oil, which is less here than in the buds, also contains eugenol.
The plant contains aromatic and phenolic compounds.
PLANTS CONTAINING AROMATIC AND PHENOLIC COMPOUNDS
Aromatic compounds in essential oils are represented by oxygen derivatives, of which the following are the most common.
Phenols in essential oils are represented by both individual compounds and phenol esters. The most common are the following.
PLANTS CONTAINING ESSENTIAL OILS
Essential oils are natural aromatic substances that are highly volatile and cause the specific smell of plants. For this reason, also due to their “oily” consistency and “greasy” stain on paper, which soon disappears, they received such a peculiar name.
Essential oils are not individual substances. These are complex mixtures of organic substances, the composition and number of which are different for each type of essential oil plants and can serve as a chemotaxonomic feature. The main group of substances that make up the essential oils of many plants are terpenes (more precisely, monoterpenes) and seseviterpenes, i.e., substances with an isoprenoid structure. However, in the essential oils of a number of plants, aromatic compounds may predominate, as well as numerous substances of the aliphatic series. There are plants with sulfur and nitrogen compounds in essential oils.
Essential oils in plants are mostly in a free state. However, some plants contain them in the form of glycosides and are released during enzymatic cleavage. Essential oils are formed in all parts of plants, but quantitatively they accumulate in them traditionally unequally.
They can be in a plant organism in a diffuse diffuse state (ie, emulsified or dissolved in cells) or accumulate, localize in special anatomical and morphological formations that are easily detected under a microscope. These excretory formations can be exogenous and endogenous.
Exogenous formations develop in the epidermal tissue and are:
– glandular “spots” – small-drop accumulations of essential oils immediately under the cuticle of the epidermis;
– glandular hairs – cylindrical epidermal outgrowths, consisting of a unicellular or multicellular pedicle and a head with cells that secrete essential oil;
– glands – epidermal outgrowths that have received the most
the highest specialization in the extraction and accumulation of essential oils. They have a different structure and can serve as a systematic feature. For example, in yasnotkovye (labial) 8 excretory cells are arranged in a rosette on a short stalk; in aster (composite) glandular cells have a vertical arrangement – 2 in 4 rows, etc.
Endogenous formations develop in parenchymal tissues and are:
– secretory cells – single (for example, in the air parenchyma of calamus rhizome) or form layers of such cells (for example, in valerian roots);
– receptacles – rounded cavities formed in the mesophyll of the leaf, peel of citrus fruits, in the bark and wood of a number of plants and filled with essential oil;
– tubules and passages – strongly elongated excretory formations found in the fruits of umbellate, bark and wood of a number of plants.
Essential oils accumulate in plants in all possible quantities: from hundredths and thousandths of a percent (for example, in violet flowers – 0.004%) to 20% or more (for example, in flower buds of carnations – up to 23%).
Essential oils are obtained: 1) by steam distillation; 2) extraction with some extractants; 3) enfleurage; 4) mechanically.
Steam distillation is the most common method. It is carried out in installations consisting of a double-jacketed still (in which steam circulates to prevent the still from cooling), a condenser and a receiver. Steam is fed into the cube loaded with raw materials from below through a perforated coil, entraining the essential oil. A mixture of cooled vapors of water and essential oil enters the receiver, where the mixture separates and excess water is removed through a tube at the bottom of the receiver (if oil is lighter than water) or through a drain tube at the top (if oil is heavier than water).
The extraction of essential oils from raw materials is carried out with volatile organic solvents in Soxhlet-type apparatuses or in column apparatuses. Subsequently, the raw material is lifted by the screw from the bottom up, and the extractant enters towards it. After distillation of the solvent, the residue is either pure essential oil or its mixture with other extracted substances (resins, waxes, etc.); in the latter case, additional cleaning is required.
Enfleurage is based on the fact that essential oil from raw materials (mainly from flowers) is absorbed by sorbents (solid fats, activated carbon, etc.) in special frame installations.
The mechanical method is used to extract essential oils from citrus fruits by pressing or scraping.
Although essential oils are very common in the plant world, their role for the plant organism and the reasons for their formation have not yet been reliably established. It was assumed that essential oils serve to protect plants from diseases and pests, to attract the smell of insects, which contributes to the pollination of flowers, to protect plants from excessive heating during the day and hypothermia at night, etc. Currently, most scientists believe that essential oils (or rather, their components) are actively involved in the metabolic processes of plant organisms.
Essential oils find a wide and varied application for medicinal, cosmetic, food (spices) and other chains.
Essential oils are classified according to the substances that make up their bulk, or substances that determine their medicinal and industrial value. There are the following groups (and subgroups) of components of essential oils:
Monoterpenes (terpenes), including:
1. Acyclic terpenes.
2. Monocyclic terpenes.
3. Bicyclic terpenes.
Sesquiterpenes, including:
1. Acyclic sesquiterpenes.
2. Cyclic sesquiterpenes.
Aromatic and phenolic compounds.
Sulfur and nitrogen-containing compounds.
The listed compounds, especially terpenoids, in essential oils can occur in the form of numerous oxygen derivatives: alcohols, aldehydes, ketones, phenols, acids, esters, lactones, oxides, quinones. The number of terpenoids also increases due to the tendency of many of these compounds to various forms of isomerism (optical, geometric, etc.).