Lecithin chemical structure

Emulsifiers. The chemical structures of emulsifiers, or surfactants, enable these materials to reduce the surface tension at the interface of two immiscible surfaces, thus allowing the surfaces to mix and form an emulsion. An emulsifier consists of a polar group, which is attracted to aqueous substances, and a hydrocarbon chain, which is attracted to lipids. Emulsifiers include mono- and diglycerides, lecithin, propylene glycol esters, luctylated esters, sorbttan and sorbitol esters, polysorbate.x, and sucrose esters. 

A change in the relative concentration of any of these components, or an alteration of their chemical structures, may cause some change in the physical or chemical properties of commercial lecithins. Lecithins can exist as liquids, plastics,... 

The simplest method for modifying natural (crude) lecithin is the addition of a non-reactive substance. Plastic lecithins are converted to fluid forms by adding 2% to 5% fatty acids and/or carriers such as soybean oil. If the additives react with the lecithin to alter the chemical structure of one or more of the phospholipid components, the resulting product is referred to as a chemically modified lecithin. Modification can also be achieved by subjecting lecithin to partial controlled enzymatic hydrolysis. Finally, refined lecithin products can be obtained by fractionating the various phospholipid components. 

Chemical structures for the most commonly occurring phospholipids in commercial soybean lecithin are shown in Figure 1 (7). PC and PE are cationic and anionic at the same time that is, they are zwitterions, and thus they can have some buffering action for both bases and acids. PI, however, is a relatively strong acid and, therefore, is anionic. The classes of compounds in commercial lecithin are as follows (31) ... 

These functional characteristics are primarily derived from the chemical structures of lecithin s major phospholipids (Figure 1) (7). Phospholipid molecules contain two long-chain fatty acids esterified to glycerol, as well as a phosphodiester bonding a choline, inositol, or ethanolamine group. A phospholipid s fatty acid end is nonpolar and thereby lipophilic (or fat loving). Conversely, the phosphodiester, with the above-mentioned constiments, is zwitterionic (or dipolar), which... 

None of the venoms, however, showed any interaction with films of cholesterol or protein, nor did hydrolysis occur in films of tripalmitin, triolein, cerebron, or sphingomyelin. The reaction with lecithin is highly specific. Not only is it sensitive to the chemical structure of the film, but the reaction rate may also be greatly altered by slight changes in the orientation of the molecules in the film or by changes in the pH of the solution or of the concentration of venom. 

Amphotropic behavior can be found for a large number of different chemical structures. Additional information is given in other chapters of this Handbook. Typical classes of amphotropic materials are for instance classical soaps (see lyotropics), transition metal soaps (see metallomesogens), viologens, quartemary amines and other ionic surfactants (see lyotropics), block copolymers (see polymer liquid crystals), cellulose derivatives (see cellulose liquid crystals) and partially fluorinated paraffines, diols, peptide surfactants, lecithins, lipids, alkylated sugars and inositols, naturally occurring glycosides and silanols, which are discussed in this chapter. 

Surfactants are classified on the basis of the charge carried by the polar head group as anionic, cationic, nonionic, or amphoteric. Tables 2.1 through 2.4 show the chemical structures of typical examples of these classes. Lecithin, cephalin, and the bile acids are ususally classified as biosurfactants. The bile acids and their conjugates have different properties in solution from surfactants with a long alkyl chain. ... 

This encapsulation procedure gives the highest activity for the lipases. The lecithin/ amines mixture structuring the pore network leads to a suitable phospholipids bilayer-like environment, which avoids the necessity to create an interface by substrate assembly. Monduzzi and coworkers compared the activity of lipase that was immobilized on SBA-15 physically, or chemically with glutardialdehyde [200]. 

Avocado produces a rather viscous oil that penetrates the upper skin layers well and is beneficial for dry skin and is often found in sun preparations. It is versatile, with applications ranging from soothing nappy rash to an ideal choice for damaged, dry and mature skin. It is a mixture of monounsaturated and saturated fatty acids, with oleic (60-70%), linoleic (8-15%), palmitoleic (4-7%), linolenic (2%), palmitic (12-16%) and stearic (2%). Vitamins A, B and D are found along with lecithin. Lecithin is one of the major phospholipids (a lipid combined with a phosphate group) of the body. Phospholipids are vital chemicals needed in the body for structural and metabolic functions. 

For the elucidation, synthesis, chemical properties, physical chemistry, composition, and analytical determination of the various individual phospholipid structures in animal and plant sources, the reader is referred to Wittcoff (4). Schneider (14) discusses the nomenclature used for phospholipids in more detail and provides compositional data on commercial lecithins (Table 14). 

The lipid membrane is made up of a variety of fat-derived chemicals, the most important of which are the phospholipids (or lecithins) and ceramides. Phosphatidylcholine (13.7) is a typical phospholipid. The molecular structure is based on glycerol, propan-1,2,3-triol. Two of the alcohol functions are esterified with fatty acids, stearic acid in this case, and the third (one of the primary alcohol functions) with phosphoric... 

Nature already produces the desired structures, and isolation of these components mostly requires only physical methods without chemical modification. Examples comprise polysaccharides (cellulose, starch, alginate, pectin, agar, chitin, and inuUn), disaccharides (sucrose and lactose), and triglycerides, lecithin, natural rubber, gelatin, flavors and fragrances, etc. 

Macro- and miniemulsions are thermodynamically unstable. If not stabilized, the droplets tend to fiocculate, coalesce, sediment or cream [2-4]. Other instabilities, such as Ostwald ripening and phase inversion, are also known. At worst, an emulsion will break, i.e. the two phases will separate completely. A product becoming unstable will lose its quality within a short period of time and thus cannot be commercialized. Therefore, even in natural emulsion-based products, amphiphilic molecules are found (e.g. lecithin and proteins in egg yolk and milk and artificial surfactants and emulsifiers in cosmetics and chemical products. They adsorb at the droplets interfaces and stabilize them against flocculation and coalescence. Adsorption and stabilization mechanisms depend on the molecular structure of a surfactant or an emulsifier as depicted in Figure 20.1. Stabilization mechanisms are summarized in... 

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