Topic of lecture: GALENIC PREPARATIONS THEORETICAL FUNDAMENTALS OF EXTRACTION

Classification of extraction preparations from herbal raw materials (HRM) by technology of receipt: 1) Total (Galen) preparations; 2) New-galen (the maximal purified or refined) preparations; 3) Preparations of individual substances.

Galen preparations are called by the name of a famous Roman physician and pharmacist Claudius Galen ( rr.n.e.) Galen preparations (GP) are extracts from herbal or animal raw materials. They are classified: - Tinctures, - Extracts (liquid, thick, dry), - Extracts-concentrates - Polyextracts Galen preparations (GP) are complex of biologically active substances are obtaining from HRM. Therapeutic effect of GP due to this complex that enhance, diminish or alter the action of basic substances.

The process of extraction is the mass changed process which has been based on the diffusion of molecules of biologically active of substances (BAS) from the internal structures of particles of herbal raw material (HRM) in the extractant and has been ends when you reach equilibrium concentrations of molecules of biologically active substances in raw and extractant.

Molecular diffusion is a process of transportation of molecules of substances (BAS) due the chaotic motion of molecules in a stationary environment. Molecular diffusion has been characterized by coefficient of molecular diffusion D, which is derived from the equation of Einstein: D= RT/6Nπrη

D= RT/6N 0 πrη R - universal gas constant, equal to 8.32 J / (mol deg); N 0 - number of Avogadro (6, ); T - absolute temperature, K; η - viscosity of solution; r - radius of Diffused particles, m.

Coefficient of molecular diffusion describes the ability of a given substance to penetrate due to diffusion in the stationary environment. D= RT/6N 0 πrη They have been increased with increasing of temperature and have been decreased with increasing viscosity of medium and particle size of molecules of BAS.

Layer of extractant is present about the wall of part of HRM. It called diffusion boundary layer, on the surface of part of HRM. This layer makes a great resistance to further transfer of extracted substances in the extractant. Its thickness depends on the hydrodynamics of the process, especially on rate of mixing at extraction. While higher the speed of mixing, the boundary layer has been thinned.

Within the diffusion boundary layer transfer of substances are legally as the first law of free diffusion and can be expressed as the first law of Fik: S=βF (C 1 -C 2 )τ/d S - number of substances that had diffused, kg; β – coefficient of convective diffusion, m/s, which is the greater at the more intensive mixing. F - surface of separation of phases, m 2. d - thickness of diffusion boundary layer, m τ - time of diffusion, s; C 1 - C 2 – difference of concentration of BAS, kg/m 3.

Extraction process depends on many factors, most important of which: hydrodynamic conditions surface of separation of phases difference of concentration duration of process viscosity of extractant temperature adding of surfactants, choice of extractant, porosity and the size of cavities between pieces of crushed HRM influence of vibrations, pulsations, electric pulse discharge in a liquid medium, strain and chop of raw in extractant.

In the presence of hydrodynamic conditions rate of the extraction is higher, because layer of stationary liquid has been decreased, there are convection currents that promote transfer of substances. The difference of concentrations of BAS in HRM (C 1 ) and in extractant (C 2 ) is drives the process of extraction. During the extraction should aspire to the maximum gradient of concentration. It is achieved by frequent changes of extractant (remaceration instead maceration), a process extraction with opposite direction of HRM and extractant et al.

The amount of BAS which had diffused through conventional layer is directly proportional to the time of extraction. Excessive times of extraction process leads to the pollution extracts by macromolecular associates. While long extraction may be undesirable processes under the influence of enzymes. It is reasonable to stop the process of extraction at some point because obtaining of more quantities of extracted substances dos not cover costs of excessive costs of extractant (alcohol, ether).

Viscosity of extraction Less viscous solutions have a greater diffusion capacity. Heating ensures reducing of the viscosity while extraction by vegetable oils. Liquefied gases: carbon dioxide CO 2, propane, butane, liquid ammonia and others is promised in this respect. Liquid carbon dioxide is chemically indifferent to the large number of active substances. Its viscosity in 14 times smaller than the viscosity of water and in 5 - than the viscosity of ethanol.

Raising of the temperature accelerates the extraction process. But: heating is possible only for water extracts because while heating loss of extraction has been increased, and thus harm and danger of working with them increases too. Polymerization of starch, peptization of substances is while using hot water, extracts in this case are mucous.

Porosity of materials – is the size of the cavities inside the plant tissue. The size of cavities between pieces of crushed material affects the speed of extraction. These characteristics of HRM cause its absorption capacity.

Influence of vibration, pulsation, shredding Using the methods of extraction, in which there are vibration, pulsation, crushing and deformation in the medium of extraction allowed to increasing speed and completeness of the extraction of raw materials.

Requirements to extractant, for to ensure complete of extraction of BAS and maximum speed of extraction 1. selectivity (maximum dissolving medicines and minimal – ballast substances), 2. chemical and pharmaceutical indifference, 3. low toxicity and flammable, 4. availability, be affordable, 5. penetrate into the pores of the HRM and through walls of cell, to provide high resolution of wet, 6. prevent the development of microflora in the infusion, 7. have a low boiling point, easily recover.

Water is one of the most suitable extractants. It has several advantages: 1. well penetrates through the cell membrane, impermeable to hydrophobic substances; 2. dissolves and extracts substance better than other liquids; 3. pharmacologically indifferent; 4. very common; 5. combustible and explosion proof; 6. available at cost.

Water, as extractant has some negative properties: 1. Can not dissolve and can not extracts hydrophobic substances; 2. Has not antiseptic properties, resulting in water extractions can develop micro- organisms; 3. Using water due hydrolytic cleavage of many substances, especially while high temperature; 4. Enzymes can destroy medicines in the aquatic environment.

Characteristic of alcohol as extractant: 1.Is the solvent for many compounds but dos not extract water, such as fats, alkaloids, chlorophyll, glycosides, essential oils, resins and others; 2. Has antiseptic properties (alcohol in aqueous solutions with concentration above 20 % do not develop bacteria); 3. The stronger of alcohol, hydrolytic processes are the less possible in its environtmental. 4. Alcohol inactivate enzymes; Quite volatile, so alcohol extract is easy dencytied and dried to a powdery substance.

Disadvantages of alcohol: 1.Is limited product, has been sold by pharmaceutical production according to the law; 2.Much heavier than water. Penetrates through the cells walls and subtracts the water in proteins and mucous substances, converts them to sediments that clog cells pores, and therefore impairs the diffusion. Whether a lower concentration of alcohol, the easier it gets inside cells; 3. Pharmacologically no indifferent, has both the local and general effect, which should be considered in the production of infusions; 4. Flammable.

Acetone Is extractant for the alkaloids, resins, oils and others. Ethyl ether mixed in all proportions with acetone, alcohol, petroleynyy ether, fatty oils and essential oils. Chloroform is a good solvent for alkaloids, glycosides, oils, oils and more. Dyhloretan is used for extracting glycosides. Methylene chloride is used for the extraction of hydrophobic substances (glycosides, alkaloids, etc.). Methanol, methyl or wood alcohol. Vegetable oil. Often used peach, almond and sunflower oils. Liquefied gases: carbon dioxide, propane, butane, liquid ammonia, chladone. Liquid carbon dioxide good extracts ether oils, fatty oils and other hydrophobic substances.