LECTURE № 4
Analysis of medicinal plants and medicinal raw material which contain lipids (macrodiagnostics). Analysis of fatty oils. Determination of purity, physical and chemical indices
Plan
1. Lipids and their classification.
2. Fatty acids: classification, nomenclature and biological functions.
2a. Prostaglandins- biologically active lipids derived from fatty acids.
3. Fats- physicochemical properties, methods of obtaining, analysis and biological actions.
4. Lipoids: their classification and main application.
4a. Phospholipids
4b. Lecithin
4c.Waxes
5. MRM which contain lipids
Lipids are naturally occurring molecules from plants or animals that are soluble in organic solvents and non-soluble in water.
Classification of lipids
There are 3 main classifications of lipids: chemical, biological and physicochemical.
In biological classification lipids are divided to reserve and structural.
By physicochemical classification there are: a) polar and non-polar (neutral) L.; b) saponificated (fats, waxes, phospholipids, glycosides) and non-saponificated (isoprenoids and prostaglandins) L.
In pharmacognosy we use chemical classification. We study here lipids, which have in their structure remains of fatty acids: fatty acids, fats and fat-like substances (lipoids).
Fatty acids
There are more than 200 fatty acids in the world. Their classification is based on the length of the carbon chain (short, medium or long); the number of double bonds (unsaturated, mono- and polyunsaturated); or essentiality in the diet (essential or non-essential).
Essential fatty acids (EFA) – are fatty acids that caot be constructed within the organism from other components, and therefore must be obtained from the diet.
There are 2 main types of EFA’s: omega-3 (linolenic, eicosapentaenoic and decosahexanoic acids) and omega-6 (linoleic and arachidonic acids). The body can convert one omega-3 acid to another omega-3, but not omega-3 to omega-6. These acids are originally designated as Vitamin F. Average daily dose of Vitamin F for adults is 10g.
Sample nomenclature for fatty acids:
Name- Carbon Length: Number of Double Bonds (Position of Double Bonds)
Saturated acids:
Butyric acid- 4:0
Palmitic acid-16:0
Stearinic acid- 18:0
Unsaturated acids:
Oleic acid- 18:1 (9)
Linoleic acid- 18:2 (9, 12)
α–Linolenic acid- 18:3 (9, 12, 15)
γ–Linolenic acid- 18:3 (6, 9, 12)
Arachidonic acid- 20:4 (5, 8, 11, 14).
Spreading and biological functions of FA’s
FA’s are the constituents of lipids. In animal lipids we can find saturated acids- palmitic and stearinic. Unsaturated FA’s are in oils – linoleic, α–linolenic.
FA’s play energetic and structural functions. They increase energy production by helping the body obtain more oxygen. They also increase oxidation rate, metabolic rate, energy levels and stamina.
Prostaglandins
Prostaglandins (PG) – are biologically active lipids enzymatically derived from fatty acids. Every PG contains 20 carbon atoms, including a 5-carbon ring. They are mediators and have a variety of strong physiological effects. Although they are technically hormones, they are not classified as such.
In 1971, it was determined that aspirin-like drugs could inhibit the synthesis of PG. The British pharmacologist John Robert Vane showed that aspirin suppressed the production of PG and he was awarded Nobel Prize in 1982 for this.
PG are used:
– for abortion and to induce a childbirth;
– to prevent and treat peptic ulcers;
– for treatment of glaucoma;
– in pulmonary hypertension;
– for treatment of bronchial asthma.
Fats
Fats are generally triesters of glycerol and fatty acids. Their main structure is:
R, R, R- polyunsaturated fatty acids with one, two, three or four double bonds.
Fats may be either solid or liquid at normal room temperature. Term “fatty oils or plant fats” is usually used to refer to fats that are liquids, while “animal fats” is used to refer to fats that are solids at normal room temperature. The examples of plant fats are peanut oil, sunflower oil, olive oil, coconut oil.
By physicochemical properties fats are classified to non-drying, semi-drying and drying.
Physicochemical properties of fats.
Fats and fatty oils are oily and they leave a sign on the paper which becomes bigger and bigger when we heat it. This feature distinguishes them from the ether oils (their sign disappears). When fats burn the fire is very bright. They are soluble in organic solvents (diethyl ether, benzole, vaseline oil, chloroform etc.)
Saponification of fats
Saponification is the hydrolysis of an ester under basic conditions to form a glycerol and the salts of fatty acids (soaps). This reaction used to make soaps and to find the constituents of fats and their quality. We use here a saponification number.
Rancidification of fats
Rancidification is the decomposition of fats and other lipids by hydrolysis and/or oxidation. These chemical processes can generate highly reactive molecules which are responsible for producing unpleasant and obnoxious odours and flavours. This kind of spoiling is controlled by acid number and peroxide number.
Drying of fats
The word “oil” is applied to those glycerides that are liquid at 20°C. Drying oils on exposure to the atmosphere are oxidising and form a thin elastic film of dry resin- lanoxin, which is unsoluble in organic solvents. They are of great importance to the paint and varnish industries. Semi-drying oils can only slowly absorb a limited amount of oxygen and will only form a soft film after long exposure to the atmosphere. Non-drying oils remain liquid at ordinary temperatures and do not form a film.
The drying of oils is very important physicochemical process which begins with the oxidation of methylenic groups near double bonds with further polymerisation and condensation etc.
Elaidic test and iodine number are the characteristics of the drying.
Oleic acid under the action of nitrous acid converts to trans-isomer – elaidic acid which has a firm consistency. The positive elaidic test means that the testing oil is non-drying. Drying oils have the highest iodine number as they consist of big amount of unsaturated fatty acids.
Hydrogenation of lipids
Hydrogenation of lipids involves the addition of hydrogen to double bonds in the fatty acid chains. Hydrogenated lipids are used as ointment bases.
Methods of fats’ obtaining
There are 3 methods of obtaining fats: squeezing or pressing, extraction or rendering. For example, Castor oil is obtained by hot pressing. Oils, which are obtained by extraction, are not used in pharmaceutical industry.
The concentrate of lipidic juices (virgin) has near 3% of impurities (waxes, vitamins, sterols, proteins, etc). These fats should be purificated by physical (filtration, centrifugation, sedimentation), chemical (sulphuric acid treatment, hydration, oxidation, etc) and physicochemical (adsorptive purification, deodorization) methods.
Analysis of fats
Fat testing consists of organoleptic analysis (colour, taste, odour and consistency), solubility establishment, qualitative analysis, identification of physical and chemical numeric characteristics. Contents of fatty acids are identified with gas chromatography. Chemical numeric characteristics are: saponification number, acid number, iodine number, ether number and peroxide number.
Acid number is the amount of potassium hydroxide in milligrams that is needed to neutralize the free acids in 1 gram of oil. By the acid number we can determine the fats’ quality. Fresh fats have almost neutral pH.
Peroxide number measure of milliequivalents of oxygen taken up by 1000 grams of investigated fat. Also known as peroxide value.
Saponification number (value) represents the number of milligrams of potassium hydroxide or sodium hydroxide required to saponify 1g of fat. It is a measure of all fatty acids present.
Iodine number (value/index) is the mass of iodine in grams that is consumed by 100 grams of a chemical substance. Non-drying oils have 80-100, semi-drying 100-140 and drying oils 140-200 units.
The ether value- indicates the number of milligrams of potassium hydroxide required for the saponification of the neutral ethers in1 g of a fat. The difference between saponification number and acid number is the ether number.
Biological functions of fats
The glycerophospholipids are the main structural component of biological membranes. Other lipid components such as sphyngomyelin and sterols are also found in biological membranes. In plants and algae lipids are important components of membranes of chloroplasts and related organelles.
Triacylglycerols, stored in adipose tissue, are a major form of energy storage in animals. The adipocyte, or fat cell, is designed for continuous synthesis and breakdown of triacylglycerols. The complete oxidation of fatty acids provides high caloric content, about 9kcal/g, compared with 4 kcal/g for the breakdown of carbohydrates and proteins.
Migratory birds that must fly long distances without eating use stored energy of triacylglycerols to fuel their flights.
In recent years, evidence has emerged showing that lipid signalling is a vital part of cell signalling. Membranes of several different lipid categories have been identified as a signalling molecules and cellular messengers.
The fat-soluble vitamins (A, D, E and K) which are lipids are essential nutrients stored in the liver and fatty tissues.
In pharmaceutical industry fats are used in production of ointments, emulsions, suppositories, as a solvent for hormones, camphor and for other fat-soluble substances.
Fat-like substances (lipoids)
Lipoids are a group of fat-like substances, as waxes or complex lipids. Lipoids are insoluble in water, soluble in organic solvents; while heated with alkali they saponificate.
Phospholipids are a class of lipids and are a major component of all cell membranes. Most phospholipids contain a diglyceride, a phosphate group and a simple organic molecule such as choline.
Functions of phospholipids.
Phospholipids act as a building blocks of the biological cell membranes in all organisms; participate in transaction of biological signals; act as efficient store of energy; play an important role in the transport of fat between gut and liver in mammalian digestion.
Lecithin is a group of substances occurring in animal and plant tissues, composed of phosphoric acid, choline, fatty acids and glycerol.
It may be isolated from egg yolk, soy beans chemically or mechanically. It also found in caviar and sunflower seeds.
Lecithin helps to maintain a structural integrity of cells; is a source of messengers to help control blood pressure and regulate insulin level. Phospholipids and lecithin are used to treat liver disorders.
Waxes
Wax is the type of lipid that may contain a wide variety of long-chain alkanes, esters, polyesters and hydroxyesters of long-chain primary alcohols and fatty acids. They are usually distinguished from fats by the lack of glycerine and three fatty acids.
Wax types
Animal waxes:
– beeswax– produced by honey bees. It used as a food additive and known as E901. Also beeswax helps to treat wounds as it has vitamin A;
– lanolin (wool wax)- produced by the sebaceous glands of sheep. Medical grade lanolin is used as a cream to soothe skin, it has hypoallergenic and bacteriostatic functions. As an ointment base it is rapidly absorbed through skin, facilitating the absorption of medicinal chemicals it carries. Lanolin is often used as a raw material for vitamin D3 production;
– spermaceti– from the head cavities and blubber of the sperm whale. Is used for ointment production in pharmaceutical industry;
Vegetable waxes:
– bayberry wax- from the surface wax of the fruits of the bayberry shrub, Myrica faya. Used in manufacturing of candles where the distinctive fragrance is desirable;
– candelilla wax- from the Mexican shrubs Euphorbia cerifera or Euphorbia antisyphilitica. As a food additive candelilla wax has the number E 902 and is used as a glazing agent. It also finds use in cosmetic industry as a component of lip balm and lotion bars;
– castor wax- catalytically hydrogenated castor oil. Is used in cosmetic products;
– jojoba oil- a replacement for spermaceti, is pressed from the seeds of the jojoba bush, Simmondsia chinensis. Jojoba oil is an ingredient in cosmetics and personal care products, especially skin care and hair care. It has fungicide action also.
Mineral waxes:
– ceresin waxes;
– montan wax- extracted from lignite or brown coal. Is used for making polishes, resins.
There are also a lot of synthetic waxes:
– polyethylene waxes;
– chemically modified waxes;
– Fisher-Tropsch waxes, etc.
MRM, which contaion-drying lipids
Olive fruits- Olivarum Fructus
Olea europaea
Oleaceae
Olive oil- Oleum olivarum
Is used as a solvent for a fat-soluble injections, as a base for liniments; also as a laxative agent, in gastric ulcer, cholelithiasis.
Almond seeds – Amygdalarum Semina
Amygdalus communis
Rosaceae
Almond oil- Oleum Amygdalarum
Is used to replace an Olive oil.
Peach seeds- Persicorum Semina
Persica vulgaris
Rosaceae
Peach oil- Oleum Persicorum
Is used to replace an Olive oil
Castor seeds- Ricini Semina
Ricinus communis
Euphorbiaceae
Castor oil- Oleum Ricini
Is used as a laxative agent; externally for treatment of trophic ulcer and seborrhoea.
MRM, which contain semi-drying lipids
Sunflower seeds- Helianthi Semina
Helianthus annuus
Asteraceae
Sunflower oil- Oleum Helianthi
Is used as a solvent for medicinal substances, as a base for patches; mild cholagolic agent.
MRM which contain phospholipids
Soybean seeds- Semina Sojae (Glycine)
Glycine hispida
Fabaceae
Soybean oil- Oleum Sojae
Essentiale– used for liver diseases;
Essel, Essaven-gel- venotonic action;
Glysabol– for metabolism correction.
Drying lipids
Flax seeds- Semina Lini
Linum usitatissimum
Linaceae
Flax oil- Oleum Lini
Reduces the cholesterol level; inflammatory disease of digestive system, laxative agent;external use- restorative function.
Solid fats
Cocoa seeds- Semina Cacao
Theobroma cacao
Cocoa butter- Butyrum cacao (Oleum Cacao)
Used as basis for suppositories.
Animal fats
Cod-liver oil- Oleum Jecoris
Fish oil, Tecom– vitamin, restorative, immune-stimulatory agent. Reduces the lipids’ level in blood.
Prepared by assist. Dakhym I.S.
