Biochemistry of Fats and Oils

Lipids: Introduction & Classifications

• Lipids are a diverse group of naturally occurring organic compounds.
• They are soluble in non-polar solvents (like ether, chloroform, acetone, benzene) but generally insoluble in water.
• Lipids exhibit significant structural diversity, encompassing fixed oils, fats, and waxes.
• Lipids have crucial physiological roles, including structural components of biological membranes, energy reserves (primarily in triacylglycerols), and as vitamins and hormones.
• Lipophilic bile acids aid in lipid solubilization.

Lipids: Introduction & Classifications

• Lipids are mainly esters of long-chain fatty acids and alcohols, or closely related derivatives.
• Simple lipids include fixed oils, fats, and waxes.
• Complex lipids include phosphatides and lecithins, containing phosphorus and nitrogen, in addition to carbon, hydrogen, and oxygen.
• Lipids can be categorized as hydrolyzable or non-hydrolyzable.
• Fatty acids are commonly found in ester combination with glycerol, forming triglycerides.
• Triacylglycerols (triglycerides) are the most abundant lipids. Upon hydrolysis, they yield glycerol and three fatty acid molecules.
• Triglycerides can be simple (all three fatty acids are identical) or mixed (two or more different fatty acids). Most natural fats and oils are mixed triglycerides.

Lipids: Introduction & Classifications

• Hydrolyzable lipids can be cleaved into smaller molecules via hydrolysis with water. Most hydrolyzable lipids contain an ester unit.
• Non-hydrolyzable lipids cannot be cleaved into smaller units via aqueous hydrolysis. They typically show more structural variation.
• Examples of hydrolyzable lipids: waxes, triacylglycerols, phospholipids.
• Examples of non-hydrolyzable lipids: fat-soluble vitamins, eicosanoids, terpenes, steroids.

Lipids: Introduction & Classifications

• All fatty acid chains are unbranched, although they may be saturated or unsaturated.
• Common saturated fatty acids include palmitic and stearic acids. Oleic acid is a common unsaturated fatty acid.
• Naturally occurring fatty acids usually have an even number of carbon atoms.
• The melting point of a fatty acid depends on the degree of unsaturation.

Structures of Common Lipids

• Diagrams of cholesterol, a free fatty acid, a triglyceride, and a phospholipid are presented.

Fixed Oils and Fats

• Fixed oils and fats are derived from plants or animals.
• In higher plants, they are primarily found in seeds, often serving as reserve food materials.
• In animals, they predominantly reside in subcutaneous and retroperitoneal tissues.
• Fixed oils and fats are categorized as liquid or solid at room temperature.
• Most vegetable-derived lipids are liquid, while animal-derived lipids are generally solid.
• Fats and oils, when metabolized, yield more calories than proteins and carbohydrates.

Fixed Oils and Fats

• Fixed oils and fats differ mainly in their melting points.
• Fixed oils and fats are insoluble in water but readily dissolve in organic solvents.
• They are lighter than water.
• They stain paper permanently and exhibit translucence.
• Prolonged exposure to air, moisture, and light can lead to rancidity due to ester hydrolysis.

Fixed Oils and Fats

• Chemically, fixed oils and fats are composed of glycerol and three fatty acids linked via dehydration synthesis; these are known as triglycerides.
• Fatty acids can be saturated, monounsaturated, or polyunsaturated.
• Saturated triglycerides tend to be solid, while unsaturated triglycerides typically remain liquid.

Examples of Saturated and Unsaturated Fatty Acids

• A table lists various fatty acids, their sources, and relevant characteristics (e.g., number of carbon atoms, position of double bonds).

Analytical Parameters for Fats and Oils

• Iodine value: Measures the extent of unsaturation in fats or oils. Higher values correspond with greater potential for rancidity.
• Saponification value: Indicates the average molecular weight of fatty acids contained within a fat or oil.
• Acid value: Reflects the amount of free acid present in a lipid sample.
• Peroxide value: Measures oxidative rancidity, related to the initial stages of lipid oxidization.
• Unsaponifiable matter: The residue remaining after saponification (a procedure used to produce soap).

Analytical Parameters for Fats and Oils (Qualitative)

• Qualitative tests involving physical constants (like specific gravity, melting point, refractive index, and optical rotation) are significant for characterizing fixed oils and fats.
• Gas chromatography is often used to separate and identify fatty acids produced through hydrolysis of certain fixed oils. This technique is significant for quality control and identification purposes.

Waxes

• Waxes are esters of long-chain fatty acids and alcohols.
• Unlike fats, waxes are saponified only by alcoholic alkali, not aqueous alkali.
• Waxes usually contain high molecular weight monohydroxy alcohols (like cetyl, melissyl, and myricyl alcohols), in addition to other components, like sterols and hydrocarbons.
• Waxes are not good food sources due to the lack of appropriate hydrolyzing enzymes.
• Waxes generally have lower iodine values than fats and oils.
• Waxes exhibit significant hydrophobic character.

Waxes

• Waxes are widely distributed in nature, especially in the leaves and fruits of many plants.
• Waxy coatings offer protection from dehydration and small predators. Common examples of waxy substances include spermaceti, beeswax, and carnuba wax.

Extraction of Lipids

• Raw materials often require pre-treatment (e.g., delinting, decortication, blanching).
• Extraction methods include using volatile organic solvents or mechanical expression (either cold or hot).
• The extraction method depends on the characteristics of the lipid being extracted and the properties of the source material.

Extraction of Lipids (Cold Expression)

• Cold expression for fat extraction is performed at low temperatures.
• The method often employs pressure to extract lipids.
• The method frequently results in the initial separation and filtration of the extracted lipid.
• Examples of lipids obtained via cold expressions are castor oil and olive oil.

Extraction of Lipids (Hot Expression)

• Hot expressions utilize pressure and heat to extract lipids.
• Often necessitates additional steps, like neutralization, washing, and bleaching.
• Examples of lipids subjected to hot expression include cottonseed oil and linseed oil.

Extraction of Lipids (Solvent Extraction)

• Solvent extraction is often employed for materials that contain a higher concentration of lipids.
• Soxhlet, Bligh & Dyer, Folch et al., and Hara & Radin methods are commonly used procedures.

General Uses of Lipids

• Fats and oils are predominantly utilized for their nutritional value, in soaps, paints, and various pharmaceutical applications.
• Waxes are employed in pharmaceutical preparations, candles, leather work, and polishes.

Pharmaceutical Important Lipids & Drugs Containing Lipids

• Various lipids are components of pharmaceutical preparations, demonstrating a diverse range of applications.

Drugs Containing Lipids: Castor Oil

• Castor oil (Oleum Ricini) is derived from the decorticated seeds of Ricinus communis.
• Major components include approximately 45-55% fixed oil, 20% protein substances (globulins, albumin, nucleo-albumin, glycoprotein), an alkaloid (ricinine), and enzymes.
• The extracted oil has a viscid, almost colorless consistency with a faint acrid taste, highly soluble in ethanol, ether, and chloroform.

Drugs Containing Lipids: Castor Oil

• Primarily composed of triglycerides, approximately 75% tri-ricinolein.
• Other constituents include di-ricinoleoglycerides with acyl groups like oleic, linoleic, dihydroxystearic, or saturated acids (palmitic or stearic).
• Castor Oil application includes use as a laxative, emollient, in the base of ointments, and more.

Drugs Containing Lipids: Almond Oil

• Almond oil (Oleum Amygdalae) is extracted from the seeds of Prunus amygdalus, a variety of almond.
• Two types: sweet and bitter almonds.
• Contains 40-55% fixed oil, 20% protein, and mucilage.
• Bitter almond oil also contains cyanogenic glycoside amygdaline.
• Primarily composed of triglycerides with significant oleic content.

Drugs Containing Lipids: Almond Oil

• Almond oil has wide application in traditional medicine due to nutritive and emollient qualities.
• It is employed in preparations for hemorrhoids and as a vehicle in injections/insertions and many cosmetic applications.
• A 2016 review suggests possible heart health benefits linked to regular almond consumption.

Drugs Containing Lipids: Coconut Oil

• Coconut oil (Oleum Cocesi) is derived from the seed kernel of Cocos nucifera.
• It's extracted via cold expression or solvent extraction.
• Primarily characterized as an oil (concrete coconut butter) below 23°C in temperate areas. It's a concrete substance at lower temperatures and becomes liquid above that temperature.
• Contains approximately 30-40% fixed oil.

Drugs Containing Lipids: Coconut Oil

• It has a high saponification value (250-264).
• Its iodine value is lower than most vegetable oils (7-10).
• It's used as a base in ointments and some shampoos.
• It's employed as a dietary component with uses in therapeutic oral medicines. It's used in many nonaqueous mediums for administering medicines.

Drugs Containing Lipids: Theobroma Oil

• Theobroma oil (Oleum Theobromatis, Cocoa Butter) is derived from roasted seeds of Theobroma cacao.
• Extensively used as a base for suppositories, pessaries, and cosmetics.
• It is employed to create creams and certain soaps.
• It is known to reduce the formation of stretch marks during pregnancy by keeping the skin supple.

Theobroma Oil: Preparation

• The preparation of theobroma oil involves separating seeds from pods and allowing them to ferment, often resulting in a color change (from white to reddish-brown) after roasting.
• The seeds are then roasted at a temperature of up to 140°C.
• The seeds' hulls are cracked.
• The resulting substance is ground into a paste (containing approximately 50% fat) also known as "cacao butter" which, at room temperature, represents "Bitter Chocolate."
• Expression of the cacao butter from the paste creates the final product.

Theobroma Oil: Characteristics

• Theobroma oil's appearance is a solid, yellowish-white substance, or, below 25°C, a brittle solid.
• It exhibits a mild chocolate-like odor and a bland taste.
• It's mostly soluble in ether, chloroform, and ethanol.
• The glycerides, which dominate the oil's structure, contribute to its distinctive melting point, which is sharp and not greasy.

This quiz explores the chemical composition and characteristics of triglycerides, fatty acids, and fixed oils. You will learn about their states at room temperature, iodine values, saponification, and more. Test your knowledge on the biochemical properties of fats and oils in plants.