Lipids 1 Lecture 7 PDF

LIPIDS 1 Dr. Algamar 12/10/2024  LIPIDS Introduction & Classifications  The lipids are a large and diverse group of naturally occurring organic compounds that are related by their solubility in non polar organic solvents (...

LIPIDS 1 Dr. Algamar 12/10/2024  LIPIDS Introduction & Classifications  The lipids are a large and diverse group of naturally occurring organic compounds that are related by their solubility in non polar organic solvents (e.g. ether, chloroform, acetone, and benzene) and are generally insoluble in water.  There is great structural variety among the lipids and comprise of fixed oils, fats, and waxes.  The lipids of physiological importance for humans have the following major functions: › They serve as structural components of biological membranes. › They provide energy reserves, predominantly in the form of triacylglycerols. › Both lipids and lipid derivatives serve as vitamins and hormones. › Lipophilic bile acids aid in lipid solubilization. PHYTOCHEMISTRY 12/10/2024 2  Introduction & Classifications  Lipids are mainly esters of long chain fatty acids and alcohols, or of closely related derivatives.  Lipids include: › Simple lipids such as fixed oil, fats and waxes. › Complex lipids such as phosphatides and lecithins which contain phosphorous and nitrogen in addition to carbon, hydrogen and oxygen. › Lipids also can be categorized as hydrolyzable or nonhydrolyzable.  Fatty acids are mainly found in ester combination with glycerol in the form of triglycerides.  Triacylglycerols, or triglycerides, are the most abundant lipids, they are tri-esters that produce glycerol and three molecules of fatty acids upon hydrolysis.  If all three esterifying acids are the same, then the triglyceride is termed simple, whereas a mixed triglyceride is produced if two or more of the fatty acids are different. Most natural fats and oils are composed largely of mixed triglycerides. PHYTOCHEMISTRYr 12/10/2024 3  Introduction & Classifications  Hydrolyzable lipids: can be cleaved into smaller molecules by hydrolysis with water. Most hydrolyzable lipids contain an ester unit.  Nonhydrolyzable lipids: can not be cleaved into smaller units by aqueous hydrolysis.  Nonhydrolyzable lipids tend to be more varied in structure. PHYTOCHEMISTRY 12/10/2024 4  Introduction & Classifications  All fatty acid chains are unbranched, but they may be saturated or unsaturated.  The most common saturated fatty acids are palmitic and stearic acids. The most common unsaturated fatty acids is oleic acid.  Naturally occurring fatty acids have an even number of carbon atoms. The melting point of a fatty acid depends on the degree of unsaturation.! PHYTOCHEMISTRY 12/10/2024 5 Structures of Common Lipids PHYTOCHEMISTRY 12/10/2024 6  FIXED OILS AND FATS  Fixed oils and fats are obtained from plants or animal.  In higher plants, fixed oils and fats are mainly found in seeds of the angiosperm, where as in lower plants they are found in fungi species such as Ergot, in which it amounts up to 60 % where they serve as a source of reserve food material. Lipids are synthesized in plants from carbohydrates.  In animals they are present in subcutaneous and retroperitoneal tissues.  These materials are called fats or oils, depending on whether they are solid or liquid at room temperature.  Most lipids from vegetable origin are liquids in nature , with the exception of few e.g. Theobroma oil. Lipids from animal origin are usually solids with exception of few e.g. Cod liver oil.  Fats and oils, when metabolized, generate more calories than proteins and carbohydrates. PHYTOCHEMISTRY 12/10/2024 7  FIXED OILS AND FATS  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.  Fixed oils and fats are insoluble in water, freely soluble in organic solvents, sparingly soluble in alcohol with exception of castor oil and coconut oil.  They are lighter than water.  They produce a permanent translucent stain on the paper and are called fixed oils. Fixed oils and fats cannot be distilled without their decomposition.  On prolonged storage, in presence of air, moisture and light, they develop rancidity due to hydrolysis of esters and formation of free fatty acids. PHYTOCHEMISTRY 12/10/2024 8  FIXED OILS AND FATS  Chemically, they are made from two kinds of molecules: glycerol and three fatty acids joined by dehydration synthesis. Since there are three fatty acids attached, these are known as triglycerides.  These fatty acids may be saturated, monounsaturated or polyunsaturated. Usually, the gylcerides of unsaturated fatty acids are liquids, where as the glycerides of saturated fatty acids of sufficient chain lengeth are solids.! PHYTOCHEMISTRY 12/10/2024 9 Examples of saturated and unsaturated fatty acids PHYTOCHEMISTRY 12/10/2024 10 Analytical Parameters for Fats and Oils  Following are the parameters used 3. Acid value: It is the amount of free acid to analyze the fats and oils: present in fat as measured by the 1. Iodine value: It is the mass of milligrams of potassium hydroxide iodine in grams that is needed to neutralize it. As the consumed by 100 g of fats or glycerides in fat slowly-decompose the acid value increases. oil. It is a measure of the 4. Peroxide value: One of the most widely used tests extent of unsaturation and for oxidative rancidity; peroxide value is a measure higher the iodine value, the of the concentration of peroxides and hydro- more chance for rancidity. peroxides formed in the initial stages of lipid oxidation. Milliequivalents of peroxide per kg of fat 2. Saponification value: It is are measured by titration with iodide ion. For oils the number of milligrams of are to be used for parental dosage forms potassium hydroxide required the maximum peroxide value is 5. to neutralize the free acids and 5. Unsaponifiable matter: The principle is saponify the esters contained the saponification of the fat or oil by in 1 g of fat under the boiling under reflux with an ethanolic conditions specified. It is a potassium hydroxide solution. measure of the average Unsaponifiable matter is then extracted molecular weight of all the from the soap solution by diethyl ether. fatty acids present. The solvent is evaporated and then the residue is dried and weighed. PHYTOCHEMISTRY 12/10/2024 11 Analytical Parameters for Fats and Oils  Qualitative tests  Certain physical constants of fixed oils and fats are significant: › Specific gravity › Melting point › Refractive index › Optical rotation (castor oil)  The gas chromatographic separation and quantification of the acids produced by the hydrolysis of specific fixed oils is an official method for their identification and quality control; type chromatograms are included in the BP/EP. PHYTOCHEMISTRY 12/10/2024 12 Analytical Parameters for Fats and Oils 12/10/2024 13 Analytical Parameters for Fats and Oils r 12/10/2024 14  WAXES  Waxes are esters of long-chain fatty acids and alcohols.  The fatty acids are same in wax and fats, but the difference being saponification. Waxes are saponified only by alcoholic alkali but the fats may be saponified either by alcoholic alkali or by aqueous alkali.  Along with fatty acids it also contains monohydroxy alcohols of high molecular weight especially cetyl alcohol, melissyl alcohol, and myricyl alcohol. Sometimes cholesterol or phytosterols are also present.  As such they are not suitable as food because hydrolysing enzymes of wax are not present in system.  Waxes in addition contain appreciable amounts of free fatty acids, hydrocarbons, free alcohols and sterols. It is thus noted that acid values of waxes are higher than those of fats and oils; and so the unsaponifiable matter.  Whereas, iodine value is relatively lower in waxes than its in fats and oils. PHYTOCHEMISTRY 12/10/2024 15  WAXES  Waxes are widely distributed in nature. The leaves and fruits of many plants have waxy coatings, which may protect them from dehydration and small predators.  Because of their long hydrocarbon chains, waxes are very hydrophobic.  Spermaceti, beeswax, carnuba wax, etc. are the examples of waxes. PHYTOCHEMISTRY 12/10/2024 16 Extraction of Lipids  Prior to extraction of lipids, the raw material may require pre-treatment such as delinting, (e.g. white cotton seeds) decortication, (e.g. castor seed and groundnuts), blanching (e.g almond seeds),…etc; this is followed by crushing or reduction of size before extraction.  Fixed oils are either extracted by volatile organic solvents or by expression.  Expression may be done on the cold or the hot using suitable hydraulic pressure. PHYTOCHEMISTRY 12/10/2024 17 Extraction of Lipids  Cold expression: › Pressing is done in the cold and liquid obtained is then filtered, skimmed or decanted. In some cases it may be purified by washing with water. › Examples of medicinal lipids obtained by cold expression are: castor oil and olive oil.  Hot expression: › Pressing is done under the effect of steam or heat. Lipids obtained by such process require additional treatment such as neutralization, washing, and bleaching e.g. cottonseed oil, linseed oil. › The remaining cake (meal), after extraction, is used for cattle PHYTOCHEMISTRY 12/10/2024 18 feed, with the exception of few such Extraction of Lipids Solvent Extraction 12/10/2024 19 General Uses Of Lipids  Fats and oils are mostly used for their nutritive value, some are used in soap and paint industries; others have different pharmaceutical uses.  Waxes are used as ingredients of some pharmaceutical preparations, some find their use in candles, leather and polish industries. PHYTOCHEMISTRY 12/10/2024 20 Pharmaceutical important Lipids & Drugs Containing 21 Lipids PHYTOCHEMISTRY 12/10/2024  Drugs Containing Lipids “Castor Oil”  Castor Oil: “Oleum Ricini” › The fixed oil is obtained by cold expression of decorticated seeds of Ricinus communis, family Euphorbiaceae. › The plant is indigenous to India, South and Central America and Brazil. › Castor seeds contain from 45-55% of fixed oil; about 20% protein substances consisting of globulin, albumin, nucleo-albumin, glycoprotein and ricin ( a toxalbumin); an alkaloid ricinine, and several enzymes. 12/10/2024 r 22 Castor Oil “Oleum Ricini”  The fixed oil is viscid, almost colourless or slightly yellowish with slight characteristic odour and faint acrid taste.  It is soluble in 2.5 volume of 96% ethanol, freely soluble in ether and chloroform.  It is mainly composed of a mixture of triglycerides, about 75% of which is tri-ricinolein. The reminder consists of di- ricinoleoglycerides with the third acyl group represinting either oleic, linoleic, dihydroxystearic, or a saturated acid (palmitic or stearic) Ricinoleic acid PHYTOCHEMISTRY 12/10/2024 23 Castor Oil “Oleum Ricini”  Castor oil is mild purgative, fungi- static, used as an ointment base, as plasticizer, wetting agents, as a lubricating agent.  It is used as laxative and emollient. The usual dose is 15 to 60 ml.  Ricinoleic acid is used in contraceptive creams and jellies; it is also used as an emollient in the preparation of lipsticks, in tooth formulation, as an ingredient in hair oil.  The dehydrated oil is used in the manufacture of linoleum and alkyl resin.  The main use of castor oil is the industrial production of coatings, also employed to make pharmaceuticals and cosmetics in the textile and leather industries and for manufacturing plastics and fibers.  Used in traditional medicine to induce labor in pregnant women, but there is insufficient evidence that castor oil is effective to dilate the cervix or induce labor PHYTOCHEMISTRY 12/10/2024 24  Almond Oil “Oleum Amygdalae”  It is the fixed oil obtained by cold expression of blanched seeds of Prunus amygdalus varitey dulcis “ sweet almond” and seeds of P. amygdalus variety amara “bitter almond”, family Rosaceae.  The tree is native to Iran, Syria and is grown in countries bordering the Mediterranean. PHYTOCHEMISTRY 12/10/2024 25  Almond Oil “Oleum Amygdalae”  Both varieties of almonds contain 40-55% of fixed oil, 20% of protein and mucilage. Bitter almond contains in addition 2.5-4% of the colorless, crystalline, cyanogenetic glycoside amygdaline.  The oil is yellow with slight characteristic odour and bland taste.  It is insoluble in ethanol, soluble in ether and chloroform.  Almond oil consists of a mixure of glycerides with component acids of the following appropriate composition: Oleic 77%, Linoleic 17%, Palmitic 5%, Myristic 1%. PHYTOCHEMISTRY 12/10/2024 26  Almond Oil “Oleum Amygdalae”  Almond oil is used as nutritive, emollient, mild laxative, for hemmorrhoids preprations, as vehicle for injections and as an ingredient in the preparation of many cosmetic articles.  A 2016 review of clinical research indicated that regular consumption of almonds may reduce the risk of heart disease by lowering blood levels of LDL cholesterol.  The almond derivative laetrile/amygdalin has been used as an alternative cancer treatment, but there is no clinical evidence to support this use. PHYTOCHEMISTRY 12/10/2024 27  Coconut Oil “Oleum Cocesi”  The fixed oil is obtained by cold expression or solvent extraction of the dried solid part of endosperm (seed kernel) of the coconut palm Cocos nucifera, family Palmae.  In temperate region below 23°C coconut oil is concrete oil (coconut butter).  The oil readily becomes rancid on exposure to air. The coconut oil has the highest saponification value, 250– 264 and the lowest iodine value, 7–10 among the vegetable oils in common use. 12/10/2024 28 Coconut Oil “Oleum Cocesi  Coconut seed contains 30-40% fixed oil which is a semi-solid, melting at 24⁰C.  It is solid white fat / colorless to light yellow oily liquid with coconut odour and bland taste.  It is soluble in 2 parts of 96% ethanol, freely soluble in ether and chloroform.  Coconut oil consists of a mixture of glycerides in which 80-85% of the acids are saturated. Lauric 50%, and myristic 20% are the major fatty acids.  Coconut oil also contains gylcerides of Caprylic and Capric acids. PHYOCHEMISTRY 12/10/2024 29 Coconut Oil “Oleum Cocesi  Coconut oil is used as base ointment, and for preparation of marine soap and shampoo.  Coconut oil is used as dietary products in many areas of the world.  In European Pharmacopoeia, fractionated coconut oil is known as ‘Thin vegetable oil’. It is useful as a non-aqueous medium for the oral administration of some medicaments. Fractionated coconut oil is used as a basis for the preparation of oral suspension of drugs unstable in aqueous media.  Diets based on medium chain triglycerides including preparations made from coconut oil are used in conditions associated with mal absorption of fat such 30 as cystic fibrosis, enteritis, and12/10/2024 PHYTOCHEMISTRY  Theobroma Oil “Oleum Theobromatis, Cocoa Butter”  It is the solid fat obtained from hot expression of roasted seeds of Theobroma cacao, family Sterculiaceae.  The plant (tree attaining 12 meters in hight) is indigenous to Mexico, but now is widely cultivated in Tropical countries.  The seeds contains 45-53% fat + 1-4% theobromine + 0.07-0.4% caffeine, 15% starch and 15% protein. Dr. Algamar 12/10/2024 31  Theobroma Oil “Oleum Theobromatis, Cocoa Butter”  Preparation of Theobroma oil carried as follow: › First the seeds are separated from the pod and allowed to ferment (the color changes from white to dark reddish-brown). › The seeds are then roasated at temperature not above 140⁰C (they loose water and develop their charcteristic odour and taste). › The seed coats are cracked and then broken kernels are separated. › The broken kernels are ground between hot rollers yielding a paste containing up to 50% fat known as “Cacao Butter”. › At room temperature, the paste form what is known as “Bitter Chocolate”. PHYTOCHEMISTRY 12/10/2024 32 › Expressing cacao butter gives the Theobroma Oil “Oleum Theobromatis, Cocoa Butter”  Cocoa butter is yellowish white solid and brittle below 25°C. It has pleasant chocolate odour and taste.  The oil is yellowish-white solid fat with slight odour and bland chocolate-like characteristic taste.  It is slightly soluble in ethanol, freely soluble in ether and chloroform.  Theobroma oil melts between 30 and 35⁰ C. it consists of a mixure of glycerides with component acids of the following approximate composition: Oleic 37%, Stearic 34%, Palmitic 26%, and Linoleic 2%.  Due to its peculiar glyceride strucure, theobroma oil owes relatively sharp melting point and its non-greasy nature. 12/10/2024 33 Theobroma Oil “Oleum Theobromatis, Cocoa Butter”  Theobroma oil is used as a base for suppositories and pessaries.  It is used as an emollient, as a base for ointments, manufacture of creams, and toilet soaps.  It reduces the formation of stretch marks during pregnancy by keeping the skin supple.  It is used as an ingredient in lotion bars, lip balms, body butters, soaps, and belly balms for expectant mothers. 12/10/2024 34 Thanks 12/10/2024 35