Учебно-методическое пособие по английскому языку для вузов. Кислякова Н.В - 12 стр.

                             The constituents of plants

   Plant constituents of medical importance represent a diverse group of chemical
compounds showing great variation in solubility and stability. The methods which
are used for their extraction either in the pure state or in the form of galenicals must
vary. The problems involved in the drying, storage and extraction of materials need
a knowledge of the general properties of the plant constituents.
  The plant constituents may be classified as follows: fatty acids, fixed oils, fats and
waxes, phenols, tannins, proteins, alkaloids, carbohydrates, gums, mucilages and
pectins, volatile oils, resins and colouring matters. The common fatty acids are
straight chain compounds which may be saturated or unsaturated. Fatty acids when
acted upon by alcalis form soaps, the sodium or potassium salts. They are prepared
by the hydrolysis of fixed oils, fats and waxes.
  Fixed oils, fats and waxes are esters of the saturated and unsaturated acids. They
may be either liquid or solid at ordinary temperatures and have vegetable origin. The
determination of the chemical constant of oils, fats and waxes is described in the
Pharmocopoeia. The amount of unsaturated acids is indicated by the iodine value. A
determination of the amount of free fatty acids present in an oil is the indication of
purity. Vegetable oils and fats occur mainly in the endosperm or embryo of the seed.
   Phenols are compounds in which one or more hydroxyl groups are united to a
carbon atom. The simpler phenols are water-soluble substances of feebly acidic
nature. In general, they are readily soluble in aqueous caustic soda. Phenols with
several hydroxyl groups are powerful reducing agents and absorb oxygen from the
air. Phenolic substances are widely distributed in plants, usually in combination with
sugars.
  Tannins are complex substances. Their molecules are built up from simple
phenolic acids. Many tannins occur in close association with simple sugars and
appear to be glycosidic in nature. Some of them have been obtained in a crystalline
state and their structures are still in doubt. In general, tannins are soluble in water,
alcohol, dilute alcali and glycerol. Their solutions have a typical taste and give green
or blue colours with solutions of iron salts. They precipitate soluble proteins from
solutions.

Follow-up activities
IV. Read the text again and replace Russian words with their English equivalents
from the text.
1. Составные части растительных веществ represent a diverse group of medical
compounds.
2. The fatty acids may be насыщенные и ненасыщенные.
3. Vegetable oils and fats occur в эмбрионе семени.
4. The simpler phenols are water-soluble substances слабокислотной природы.
5. Tannins are сложные вещества.
6. Solutions of tannins have a типичный вкус.
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