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Tree Extractives

Tree Extractives


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By Dra. Esther Álvarez Godoy

Tree extractables are an important source of phytochemicals. Forestry development must focus its attention on obtaining from the tree everything that it can provide to man, provided that the mechanisms used are respectful with the environment.

Summary

In addition to cellulose, hemicelluloses and lignin, trees contain other substances to a lesser extent, which do not enter into the composition of cell walls. These are the extractives. Chemically they are composed of aliphatic and aromatic hydrocarbons, terpenes, phenols, fatty and resinous acids, resins, fats, sterines, essential oils and others.


The amount and composition of them depends on the species, the part of the tree, the time of year, the growing conditions and other factors. In this work, the results of the search in various bibliographic sources on the content of the extractives in different parts of the tree have been compiled. This can be a reference material for wood chemistry researchers and forestry students.

Introduction

All wood species and most vegetables contain varying amounts of some chemicals other than carbohydrates and lignin that make up the cell wall. According to the point of view with which they are dealing, they receive various names:

· Foreign components of wood, because they are different from the compounds that make up the cell wall.
· Extractable or soluble substances.
Extractive
· Volatile substances, because many of these substances are volatile or impart odor characteristics to wood.
Minor constituents

The extractables found in plant tissues are substances such as terpenes, phenols, tannins, minerals, sugars, aliphatic and aromatic hydrocarbons, aliphatic and aromatic acids, sterines, essential oils, fatty and resinous acids, resins, fats and others.

There is considerable variation in the distribution of extractables in a tree; they are found distributed in foliage, wood, bark and roots. The bark and roots are the parts where extractables are found in the highest concentration (Emilianova, 1969).

Developing

Foliage extractives

They range between 30-36%. They can be divided into two large groups: substances soluble in water and those soluble in organic solvents.

Water soluble substances.

The foliage contains a considerable amount (up to 30%) of water-soluble substances, which belong to different classes of compounds, which could be classified as follows: Vitamins (C, B1, B2, B6, H, folic acid), compounds nitrogenous (protein and non-protein), acids, phenolic substances, sugars (mono and oligosaccharides) and ashes (macro and microelements)

Soluble in organic solvents

The chemical composition of substances soluble in organic solvents is very varied. In organic solvents mainly fats, resins and fatty acids, esters of these acids, wax, phytosterins are extracted (Tamchuk, 1973).

Both the amount and the composition of these substances depend on the solvent in which they are extracted. In the literature they appear under different names: lipids, fat-soluble substances, resinous substances, crude fat and others.

According to current ideas, the substances that form living organisms, insoluble in water, but soluble in organic solvents (chloroform, ether, benzene, and others) and that contain higher alkyl radicals in their molecules, are called lipids. These substances are hydrocarbons, alcohols, aldehydes, derivatives of fatty acids (glycerides, waxes, phospho, glycol, sulfolipids), fat-soluble vitamins (A, D, E, K) and their derivatives, chlorophyll, carotenoids, sterines, etc. The inclusion of these substances in the composition of lipids is explained because they are frequently found in membranes and appear together with phospholipids and in solvent extracts used for fat extraction (Yagodin, 1981).

Essential oils

They are products of the vital activity of plants formed by complex mixtures of different substances, colorless or slightly yellow colored liquids, with a specific smell and burning taste (Tamchuk, 1973).

They constitute a mixture of volatile substances that belong to different classes of organic compounds. Oxygenated terpenes and terpenoids (alcohols and acids), some phenols, ethers, aldehydes, ketones and lactones predominate (Jolkin, 1989).
Terpenes are hydrocarbons of composition C10H16 (derivatives of isoprene C5H10). Monoterpenes, diterpenes (C20H32) and sesquiterpenes (C15H24) appear in essential oils (yagodin, 1989).

Essential oils protect the tree from fungal and insect diseases and the greatest industrial use is reached in perfumery to provide aroma to the products.

Researchers from the Institute of Pharmacy and Food, University of Havana quantified the essential oil content of the endemic Pinus caribaea Morelet species of Cuba, based on the age of the tree. The results obtained showed that the essential oil content varies significantly with the age of the tree in an ascending way, with the lowest value (0.12% by weight) at 8 years and the highest (0.27% by weight) at 30 years (Quero, et al, 2000).

Extractives from wood.


Substances extractable from wood are those substances that are extracted from different parts of coniferous and broadleaf trees by means of water, organic solvents, water vapor and by means of mechanical squeezing (Vidorov, 1987).

Among the extractable substances are the most diverse organic and inorganic compounds and their presence in different species is relative.

Sugars, starch, and some nitrogenous compounds are found in sapwood. Phenolic substances are normally found in the heartwood. There is a variation in the concentration of extractables along the trunk of the tree and between it and the branches. When the structure of the wood is studied, it is observed that the fats are located in the parenchymal cells, especially in the parenchymal rays, while the resin is secreted by the epithelial cells and they are deposited in the resin canals. Other substances are deposited in the pores of the wood (Díaz, 1986).

This distribution is governed by a series of factors, among which those of genetic and ecological significance can be highlighted. Its composition and relative quantity depend on various factors such as species, age and region.

Approximately 3-10% of dry wood is made up of extractable substances. For conifers this figure ranges between 5-8% and for broadleaves, between 2-4% (Otero, 1988).

These constituents are responsible for some characteristics of plants such as natural resistance to rot, taste and abrasive properties. Heartwood extractives are considered responsible for imparting very characteristic odors and flavors to certain wood species, such as the "pencil" smell of spruce wood, Mexico, or the unpleasant bitter taste of amargoso, Guatemala. Some species to which the extractives impart an intense aroma and flavor are also very resistant to attack by fungi and insects (Echenique, 1993).

The production of extractable substances from wood is divided into two fundamental groups:

1) Production of rosin and turpentine from resin, by distillation.

Rosin. It is a brittle substance with a vitreous appearance, a color that ranges from light yellow to brown, soluble in most organic solvents. It is made up of an amorphous mixture of up to 98% of resinous acids and non-saponifiable neutral substances. The pine resin rosin is made up of 92% of a mixture of resinous acids; 0.4 - 1.6% of fatty products and 6.4% of neutral products (Tamchuk, 1973).

Turpentine. It constitutes the volatile fraction of the resin. It is made up of a mixture of terpenic hydrocarbons (general formula: C10 H16). Almost all of these hydrocarbons have a tendency to isomerization through the action of acids, high temperature, light, catalyst, and other factors.

2) Obtaining products derived from rosin and turpentine

Rosin derivatives. They are more often called modified rosins. They are products of various reactions such as polymerization, chlorination, hydrogenation, oxidation, etc .; resinous acids (abietic, levopimaric, dextropimaric); synthetic resins; resinates (from Ca, Zn, Mn, Pb, Cu) ¸emulsifiers, etc.

Turpentine derivatives. Pinenes (a and b), camphene, camphor and others stand out.

Bark extractives

They are divided into lipophilic and hydrophilic, although there are no boundaries that delimit them. The content is higher than in wood. It varies between 20-40% dry bark mass. It includes a heterogeneous group of substances (Sjöström, 1981).

Lipophilic fraction

Extractable with apolar solvents (ethyl ether, dichloromethane, etc.). They consist of fats, waxes, terpenes and terpenoids and higher aliphatic alcohols. Terpenes, resinous acids and sterols are located in the resin channels. Triterpenoids abound: B-sitosterol found in waxes, betulinol.

Hydrophilic fraction

It includes those extractable in water alone or with polar solvents (acetone, ethyl alcohol, etc.). They contain large amounts of phenolic constituents, many of them, especially condensed tannins (phenolic acids) can be extracted only as salts with dilute alkali solution. For example, a considerable amount of flavonoids belongs to the group of condensed tannins are present in the bark of fir, oak, redwood. Monomeric flavonoids including quercetin and dihydroquercetin are also present in the bark. Small amounts of lignans and stilbenes are also found. In less quantity are carbohydrates, proteins and vitamins.

It is known that the phenolic and terpenoid components have antifungal, antibiotic, antioxidant, allelopathic and other properties (Sattler, 1993). These compounds have earned a reputation for their activity in plants as the control of insect attack and microbial diseases.

Jolkin (1989) reports 7.5% of ethanol-soluble substances for pine bark. Bedrin (1987) in pine, for mechanized debarked wood, reports 8.0% of water-soluble substances; 8.1 soluble in ethyl ether and 8.6% soluble in benzine, as well as much higher values ​​for bark that has been manually separated.

When studying the chemical composition of wood and bark of Picea orientalis (L) Link in Turkey, it was found that the content of lipophilic extractives in wood is between 0.4 - 0.6%, while in the bark it is 4, 5-6.4% (Hafizoglu, 1997).

Twenty-six phenolic compounds were found in the bark of Pinus silvestri from Sweden, being the major constituents of the catechin and proanthocyanidin groups (Pan, 1995).

In Cuba, Martínez (1983) has reported a yield of 8.29% of Pinus caribaea bark tannins and 10.19% of Pinus cubensis.

Results of the project "Alternative uses of anacardiaceae bark" in Argentina, show that the tannin-producing forest bark represents 20% of the total volume of the tree trunk and that it is currently wasted (Jiménez, 1995). In the Santiago del Estero region they studied the antioxidant properties.


The pine bark Pino cubensis G contains oligomeric proanthocyanidins, a class of flavonoid that is very powerful in its antioxidant action; it keeps the connective tissues soft and has anti-inflammatory and anti-cancer properties, report researchers from the Superior Institute of Basic and Preclinical Sciences "Victoria de Girón" (García, et al., 2001).

Bioactive extracts with antifungal activity were obtained from the bark of Pinus caribea M; otrelet var. Hondurans from forest plantations in eastern Venezuela, which also showed free radical trapping activity (Varga, 2002).

Tannins

Tannins are substances that are produced in various parts of plants, such as: bark, fruits, leaves, roots and seeds; Despite having a common origin, the specificity of the plants gives the tannins differences in color, quality and concentration.

Tannin is a compound that oxidizes on contact with air, is odorless and has a sour taste, soluble in water, alcohol and acetone; reacts with ferric chloride and other salts; it is combustible with a flash point of 199ºC, an auto ignition temperature of 528.5ºC; slightly toxic by ingestion or inhalation.

From the biological point of view, tannins are complex substances produced by plant species that perform antiseptic or conservation functions. The classification of tannins is based on the following two criteria:

Products resulting from dry distillation: hydrolyzable tannins and condensed tannins
Origin: physiological tannins and pathological tannins.

Hydrolyzable tannins, in turn are divided into:
a) Gallotanins characterized by the presence of gallotanical acid, it is common in the galls of the oak and in the root of the sumac;
b) Elagitannins, their main component is ellagic acid, they are obtained from plants such as dividivi and microblain.

Condensed tannins, generally present in the wood, bark and roots of plants such as quebracho, sour cane, eucalyptus, oyamel and mangrove, among others; They are made up of flavonoid units, which support various degrees of condensation, carbohydrates and amino acid residues.

Physiological tannins are the result of the metabolic functions of the plant.

Pathological tannins are a response to insect attack, either by oviposition or by stinging.

The tanning technique has been known since 1000 years B.C., but it is until the period 1790-1800, in France, when the base chemicals for tanning hides were isolated and discovered (Prance and Prance, 1993). Tannins are highly astringent acids, a property that has identified them as useful ingredients in traditional medicine; They are also used in food preparation, fruit ripening; beverage ingredients such as cocoa, tea, and red wine.
When tannins are mixed with iron salts, a blue-green color is produced, which is the basis for the production of inks (Prance and Prance, 1993).

Tannins occur in species of plant families around the world, approximately 500 species of plants that contain various amounts of tannins have been identified, among the main botanical families with importance in obtaining tannins, the following can be mentioned: Leguminosae, Rosaceae, Polygonaceae, Fgaceae, Rhyzophoraceae, and Myrtaceae.

Some genera such as acacias (Acacia spp.), Oaks (Quercus spp.) And some pines (Pinus spp.) That inhabit pine-oak forests or transition zones are important in the production of these products. The use of some natural substances, specifically polyphenolic structures such as oligomeric catechins and flavonoids, has proven to be a source of protection for the body. Its antimicrobial, antioxidant, photoprotective properties, as well as protease inhibitors such as elastase, are recognized. Given the structural similarity, the condensed vegetable tannins of different forest species were studied, namely: pine, casuarina, mimosa, pine cones, eucalyptus and soplillo.

In recent years, special attention has been paid to the study of new substances with physicochemical characteristics capable of preventing disorders that lead to skin mutations caused by ultraviolet radiation; Thus, the condensed vegetable tannins of different forest species were studied, namely: pine, casuarina, mimosa, pine cones, eucalyptus and soplillo by researchers from the Center for Biomedical Research and the Higher Institute of Nuclear Sciences and Technologies. In the results, it was observed that the tannins of all plant species were capable of protecting bacteria against the damage of ultraviolet radiation, which coincides with good antioxidant and anti-elastase activity; the latter 2 were lower for eucalyptus (González, et al., 2001).

Conclusions

Tree extractables are an important source of phytochemicals. Forestry development must focus its attention on obtaining from the tree everything that it can provide to man, provided that the mechanisms used are respectful with the environment.

* Bibliographic study
University of Pinar del Río. Cuba

Bibliography
· Díaz, A. Science of wood. Ministry of Higher Education. Havana, 195p.1986.
· Echenique, R. Science and Technology of wood I. University Texts. Universidad Veracruzana, Mexico, 1993
· Emilianova, I. Z. Chemical-technical control of hydrolytic productions. Edit. Lesnaya Prom. Moscow. 366 p.1969
· García, L, et al. Plants with antioxidant properties. Cuban Journal of Biomedical Research. 20 (3): 231-5. 2001
· González, Y; Peñaz, M; Sánchez, R and Santana, J.L. Tannins of different plant species in the prevention of photoaging. 20 (1): 16-20. 2001.
· Jolkin, Y. I. Technology of hydrolytic productions. Moscow, 496 p.1989
· Otero, M. Celulosa e papel. Technology of manufacture of cellulosic pulp, Sao PauloPp. 45-68. 1988.
· Sjostrom, E. Wood Chemistry. Fundamentals and Applications. Academic Press. New York. .223 p.1981.
· Tamchuk, R. and Tamchuk, G. N. Foliage and its use in agriculture. 360 p. 1973.
· Yagodin, V. Foundations of Chemistry and Technology for the treatment of foliage. Ed. Leningrad. Universitieta. pp 47-50. 1981
· Varga, J. Behavior of some extracts of the Caribbean pine bark (Pinus caribaea var. Hondurensis) on the growth of xylophagous fungi and their antioxidant action. Thesis presented as an option to the degree of Doctor in Forest Sciences. University of Pinar del Río. Cuba. 2002.


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