Lipids PHMD 232 2024 Lecture Notes PDF

Lipids PHMD 232 2024 Emelia Oppong Bekoe B.Pharm, M.Pharm, PhD UGSoP, University of Ghana, Legon Learning outcomes Describe the occurrence and sources of fixed oils, fats, and waxes in natural substances. Explain the various methods of ext...

Lipids PHMD 232 2024 Emelia Oppong Bekoe B.Pharm, M.Pharm, PhD UGSoP, University of Ghana, Legon Learning outcomes Describe the occurrence and sources of fixed oils, fats, and waxes in natural substances. Explain the various methods of extraction used to obtain fixed oils, fats, and waxes from their natural sources. Identify the physical properties, such as appearance, texture, and melting point, of fixed oils, fats, and waxes. Evaluate the pharmaceutical significance of selected oils, fats, and waxes commonly used in medicinal formulations, such as: Castor oil, Cod-liver oil, Shark liver oil, Olive oil, Coconut oil etc. etc. , Beeswax 2  Lipids These are naturally occurring organic compounds which are are defined by their solubility in nonpolar organic solvents (e.g. ether, chloroform, acetone, and benzene) and insoluble in water. They are comprised of fixed oils, fats and waxes. They serve as structural components of biological membranes. They provide energy reserves, predominantly in the form of triacylglycerols. Both lipids and lipid derivatives serves as vitamins and hormones  Lipids Lipids (fixed oils, fats and waxes) are esters of long-chain fatty acids and alcohols or of closely related derivatives. The chief difference between these substances is the type of alcohol. in fixed oils and fats, glycerol combines with the fatty acids in waxes, the alcohol has a higher molecular weight. acetyl alcohol [CH3(CH2)15OH].  Fats and oils Fixed oils and fats are obtained from plants or animal. They are rich in calories and in plant source; they are present mostly in the seeds. They differ only according to their melting point and chemically they belong to the same group. If a substance is liquid at 15.5 – 16.5 °C it is called fixed oil and solid or semisolid at the above temperature, it is called fat. They float in water since their specific gravity is less than 1.  Fats and oils Fats and oils are made from two kinds of molecules : glycerol (a type of alcohol with a hydroxyl group on each of its three carbons) and three fatty acids joined by dehydration synthesis. Since there are three fatty acids attached , these are known as triglycerides. Triglyceride Where R1,R2, and R3 are long alkyl chains The three fatty acids R1COOH ,R2COOH , R3 can all be different, all the same, or only two the same.  Structure of fatty acids The “tail” of a fatty acid is a long hydrocarbon chain, making it hydrophobic. The “head” of the molecule is a carboxyl group which is hydrophilic. Fatty acids are the main component of soap , where their tails are soluble in water to emulsify and wash away the oily dirt. However, when the head end is attached to glycerol to form a fat, that whole molecule is hydrophobic.  Structure of fatty acids Since fatty acids in these triglycerides contain the maximum possible amount of hydrogens, these would be called saturated fats. The hydrocarbon chains in these fatty acids are, thus, fairly straight and can pack closely together, making these fats solid at room temperature.  Structure of fatty acids Oils mostly from plant sources have some double bonds between some of their carbons in the hydrocarbon tail, causing bends or ‘kinks’ in the shape of the molecules. Because some of the carbons share double bonds, they are not bonded to as many hydrogens as they could if they were not double bonded to each other. Therefore, these oils are called unsaturated fats. Because of the kinks in the hydrocarbon tails, unsaturated fats (or oils) cannot pack as closely together, making them liquid at room temperature.  Structure of fatty acids Although most vegetable oils are liquid at ordinary temperatures and most animal fats are solid, there are notable exceptions, such as cocoa butter, which is a solid vegetable oil and cod liver oil, which is a liquid animal fat.  Structure of fatty acids In unsaturated fatty acids, there are two ways the pieces of the hydrocarbon tail can be arranged around a C-C double bond (cis and trans). In cis bonds , the two pieces of the carbon chain on either side of the double bond are either both ‘up’ or both ‘down’, such that both are on the same side of the molecule. In trans the two pieces of the molecule are on opposite sides of the double bond ,that is ,one is ‘up’ and one is ‘down’ across from each other.  Structure of fatty acids Naturally occurring unsaturated vegetable oils have almost all cis bonds but using oil for frying causes some of the cis bonds to convert to trans bonds. If oil is used only once like when you fry an egg, only a few of the bonds convert to the trans, however, if oil is constantly reused, like in fast food French fry machines, more and more of the cis bonds are changed to trans until significant numbers of fatty acids with trans bonds build up. The reason for this concern is that fatty acids with trans bonds are carcinogenic or cancer causing. FATS VS FIXED OILS FATS FIXED OILS 1.Mostly contain saturated fatty acids 1.Majority of the fixed oil contains unsaturated fatty acids 2.Solid at room temperature 2.Liquid at room temperature 3.Higher melting point 3.Lower melting point Fixed oil Fixed oils Properties Sources Uses Chemical composition Tests Minor components Specific examples Extraction methods 16  Fixed Oils Definition: Fixed oils, also known as non- volatile oils, are glycerides of fatty acids that do not evaporate at room temperature and are not volatile. Characteristics Composed mainly of triglycerides. Insoluble in water but soluble in organic solvents. Extracted primarily through cold pressing or solvent extraction. Used in food, pharmaceuticals, cosmetics, and industrial applications  Examples of Fixed Oils Castor oil Almond oil Olive oil Cotton seed oil Peanut oil Corn oil Soybean oil Safflower oil Sesame oil Cocoa butter  Sources of Fixed Oils Plant Sources: Seeds: Sunflower, sesame, flaxseed Fruits: Olive, avocado Nuts: Almond, coconut Others: Castor, soybean Animal Sources: Fish: Cod liver oil. Other: Lard, tallow Chemical Composition Triglycerides: Esters derived from glycerol and three fatty acids. The type of fatty acids (saturated, monounsaturated, polyunsaturated) determines the oil's properties. Fatty Acids: Saturated Fatty Acids: No double bonds (e.g., palmitic acid, stearic acid). Monounsaturated Fatty Acids: One double bond (e.g., oleic acid). Polyunsaturated Fatty Acids: Multiple double bonds (e.g., linoleic acid, alpha-linolenic acid). Fixed Oils & Fats : CHEMISTRY Fixed oils are esters of fatty acid with glycerol. These may be – Monoglycerides Diglycerides Triglycerides Chemical Composition Minor Components: Vitamins (e.g., Vitamin E). Sterols (e.g., beta-sitosterol). Phospholipids. Tocopherols. Methods of Extraction 1. Cold Pressing: Mechanical process without heat. Oil expelling is a mechanical method of extracting oil from seeds or nuts by applying pressure using an expeller press. The expeller press can be a screw press or a hydraulic press, and the process involves several steps Retains natural nutrients and antioxidants. 2. Solvent Extraction: Uses solvents like hexane to dissolve oils from plant material. The solvent is then evaporated, leaving behind the oil. Methods of Extraction 3. Extraction by expression Mechanically crushing the seeds or nuts and then pressing them to extract the oil. This can be done using various types of presses, such as hydraulic presses or screw presses. Fixed oils are obtained by expression in hydraulic presses. If the expression is carried out in the cold , the oil is known as a “virgin oil” or a ‘cold pressed oil. In contrast, if the expression is carried out in the heat , the oil is known as a ‘hot- pressed oil’. Methods of Extraction 4. Refining: Involves degumming, neutralization, bleaching, and deodorization. Produces oils with improved shelf life and sensory qualities but may reduce nutrient content. 5. Animal Fat Rendering Animals fats are separated from other tissues by rendering with steam, with or without pressure. The heat melts the fat, which rises to the top and may be separated by decantation.  Uses of Fixed Oils 1. Nutritional: Source of essential fatty acids. Used in cooking and food preparation (e.g., olive oil, canola oil). 2. Pharmaceutical: Used as carriers for drug delivery (e.g., castor oil). Emollients and moisturizers in topical formulations. Uses Of Fixed Oils 3. Cosmetic: Ingredients in skincare and haircare products. Provide hydration, nourishment, and protection 4. Industrial: Used in the production of biodiesel. Lubricants and soaps. Uses Of Fixed Oils Suppositories, tablet coating Dietary supplements Emulsifying agents Manufacture of paints, varnishes and lubricants Therapeutic uses (castor oil) CASTOR OIL Synonyms: Castor bean oil, castor oil seed, Ricinus oil Biological Source: It is the fixed oil obtained by cold expression of the seeds of Ricinus communis Linn., belonging to family Euphorbiaceae. Geographical Source: It is mainly found in India (Gujarat , Andhra, Pradesh), Brazil , America, China, Thailand Preparation 1. Castor oil is obtained from castor seeds. 2. The oil is obtained by two ways: By removal of the seed coat, or With the seed coat 3. By using grooved rollers seed coat are removed and then they are subjected to a current of air to blow the testas. 4. The kernels are fed in oil expellers and then they are expressed under high pressure (at room temperature) in order to obtain about 30% oil. Preparation 5.Then oil is filtered and steamed 80 – 100 Degrees to facilitate the coagulation and precipitation of poisonous principle ricin, proteins and enzyme lipase present in it. 6.Oil is then filtered and this oil with 1% acidity is used for medical purpose. 7. The oil cake (contains of ricin, lipase and about 20% oil) which remains is grounded, steamed and expressed under high pressure which yields second quality of oil with 5% acidity and is used for industrial purpose. 8. The residual cake which remains after the expression of the second quality oil still contains about 8% to 10% and extracted by Soxhlet apparatus which is used as manure and not fed to animal due to the presence of ricin. The cake is also used for the production of lipase. Chemical Constituents Castor oil consists of glyceride of ricinoleic acid, isoricinoleic, stearic, and dihydroxy stearic acid (responsible for laxative activity). Ricinoleic acid, binds to receptors on the smooth muscle cells of your intestinal walls, and it is absorbed. It causes those muscles to contract and push out stool, just as other stimulant laxatives do. Castor oil is non-edible oil, defers from all other oils as having ricinoleic acid as a major constituent. Compared to all other oils castor oil is highly viscous, less soluble in hexane and more soluble in ethanol as a consequence of presence of ricinoleic acid which is a hydroxyl fatty acid. Olive oil Olive oil Is the fixed oil obtained from the ripe fruits of Olea europaea. Family : Oleaceae Olive oil is a pale yellow or light greenish yellow liquid with a mild but characteristic odor. Constituents: Glycerides of – ✓Oleic acid(75%), Linoleic acid (9%), Stearic acid, Arachidic acid, Palmitic acid Uses: Laxative, Nutrient, Emollient, Demulcent (an agent that forms a soothing film over a mucous membrane, relieving minor pain and inflammation), PEANUT OIL or ARACHIS OIL Peanut oil is the refined fixed oil obtained from the seed kernels of Arachis hypogaea. Family :Leguminosae Constituents: Glycerides of ✓Oleic acid (50-65%) ✓Linoleic acid (18-30%) ✓Palmitic acid (8-10%) ✓Stearic acid ,Behenic acid, Arachidic Acid and Lignoceric acid (10-12%) PEANUT OIL or ARACHIS OIL Uses: ✓Vehicles in emulsions, liniments, plasters, soap. ✓Ink manufacture ✓Preparation of hydrogenated vegetable oil. COCONUT OIL Botanical origin Coconut oil is obtained from dried solid part of endosperm of Cocos nucifera. Family : Palmae Plant part used : Dried solid part of endosperm COCONUT OIL Constituents: Glycerides of – ✓Lauric acid (50%), Myristic acid(20%), Capric acid, Caprylic acid, Caproic acid, Oleic acid, Palmitic acid, Stearic acid Uses: ✓Confectionaries ✓Cosmetics ✓Ointment base Tests for Fixed Oils  Purpose: To identify, quantify, and determine the quality and purity of fixed oils. Significance: A combination of qualitative and quantitative tests provides a comprehensive analysis. Essential for quality control in food, pharmaceutical, and cosmetic industries  Qualitative Tests Organoleptic Evaluation: Principle: Sensory analysis based on appearance, odor, and taste. Procedure: Observe the color and clarity of the oil. Smell to detect any rancid or unusual odors. Taste (if safe) to check for any off-flavors. Result: Initial assessment of quality and possible contamination Solubility Test: Principle: Assessing solubility in various solvents. Procedure: Mix the oil with solvents such as ethanol, ether, and chloroform. Observe the solubility behavior. Result: Fixed oils are insoluble in water but soluble in organic solvents like ether and chloroform. Spot Test: Principle: Determines the presence of fixed oils through their ability to leave a translucent spot on paper. Procedure: Place a drop of oil on a piece of filter paper. Allow it to stand and observe the spot. Result: A persistent translucent spot indicates the presence of a fixed oil. Quantitative Tests Iodine Value: Principle: Measures the degree of unsaturation in the oil. Procedure: 1.Dissolve the oil in chloroform. 2.Add iodine monochloride solution. 3.Allow the reaction to proceed and add potassium iodide. 4.Titrate the liberated iodine with sodium thiosulfate. Result: A higher iodine value indicates a higher degree of unsaturation.  Quantitative Tests Saponification Value: Principle: Measures the amount of alkali required to saponify a given amount of oil. Procedure: 1.Heat the oil with an alcoholic potassium hydroxide solution. 2.Titrate the excess alkali with hydrochloric acid. Result: Provides information on the average molecular weight of fatty acids in the oil. Higher values indicate shorter chain fatty acids.  Quantitative Tests Acid Value: Principle: Measures the free fatty acids present in the oil. Procedure: 1.Dissolve the oil in a solvent mixture (ethanol and diethyl ether). 2.Titrate with a standardized sodium hydroxide solution using phenolphthalein as an indicator. Result: Higher acid value indicates a higher concentration of free fatty acids, implying hydrolysis or rancidity. Peroxide Value: Principle: Measures the extent of primary oxidation by quantifying peroxides in the oil. Result: Higher peroxide value indicates higher levels of oxidative rancidity Ester Value: Principle: Indicates the amount of ester present in the oil, derived from the saponification and acid values. Result: Provides insight into the ester content of the oil, reflecting the level of esterification. Refractive Index: Principle: Measures the degree to which light is bent as it passes through the oil. Procedure: Place a drop of oil on a refractometer. Measure the refractive index at a specific temperature. Result: Each oil has a characteristic refractive index, which can indicate purity and quality. Specific Gravity: Principle: Measures the density of the oil relative to water. Procedure: Use a pycnometer or a digital density meter to measure the oil's specific gravity at a specific temperature. Result: Provides information about the purity and concentration of the oil. Waxes Like fats, waxes are esters of fatty acids. The alcohol, however, is not glycerol but usually a long-chain, high-molecular weight alcohol e.g. cetyl and stearyl alcohols In plants, waxes are generally found covering the external parts, like the epidermis of leaves and fruits, where their main function is to prevent the loss of water. Wax is also produced by insects , e.g. the honeycombs of bees and wasps. Waxes USES OF WAX Wax is used in pharmacy to make soft ointments harder and to prepare lip salves. The technical uses of waxes are substantial e.g. in the shoe polishes and car waxes. Waxes Wax has a melting point above approximately 45 degree celsius (which differentiates waxes from fats and oils). Fats and oils may be saponified by means of either aqueous or alcoholic alkali but waxes are only saponified by alcoholic alkali (this fact is used for the detection of fats when added as adulterants to waxes). Examples of waxes Jojoba wax (Simmondsia chinensis) Carnauba wax ( Copernicia cerifera) Beewax (Apis mellifera) BEES WAX OR YELLOW WAX Bees wax or yellow wax Source: Bees wax or yellow wax is the purified wax obtained from the honeycomb of the bee Apis nullifera, Family : Apidae It is a solid varying in colour from yellow to greenish brown. Constituents : ✓Esters of fatty & wax acids (72%), chiefly myricyl palmitate ✓Free wax acids (14%), chiefly cerotic acid ✓Hydrocarbons (12%) BEES WAX OR YELLOW WAX USES : ✓In foods and beverages, white beewax and beewax absolute (yellow beewax treated with alcohol), are used as a stiffening agent or edible coatings. ✓Component of yellow ointment, cold creams. ✓Beeswax is used in the preparation of ointments, plasters, fragrant and long-burning candles, body care products, and polishes ✓Beeswax – based nanoparticles used in topical applicated protect the skin and increase hydration. BEEWAX Swarm bees, the bees that set out to start a new hive, gorge on the honey stored in their current hive in order to produce the beeswax needed to start their new colony. The bees then digest the honey and convert the carbs into liquid beeswax. Beeswax is produced from a gland in the abdomen of honeybees and is excreted to create the hive itself. The female worker bees have 8 glands in their abdomens to produce the wax when it is time to build the honeycomb.  BEEWAX The wax that is secreted hardens as soon as it hits the air and forms a wax scale. After removal of honey, honeycomb is melted in boiling water. On cooling the melted wax gets solidified and floats on the surface of water while the impurities settle below and honey leftovers get dissolved in water. The pure wax is then poured into earthen vessels wiped with damp cloth and the wax obtained is yellow wax. BEEWAX The yellow beeswax is run on a thin steam of spinning wet drum, from which long ribbon like strips are scrapped off. White beeswax is further obtained by bleaching of yellow beeswax under sunlight. Then chemically obtained with potassium permanganate , chromic acid or chlorine or charcoal. ADULTERANTS Beeswax is adulterated by solid paraffin, ceresin, carnauba wax, or other fats and waxes of animal or mineral origin.