Lecithin

• USP–NFLecithin

Egg lecithin; Epikuron; Lipoid; mixed soybean phosphatides; Phospholipon; soybean lecithin; vegetable lecithin; E322

Complex mixture of acetone-insoluble phosphatides (mainly phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol) with triglycerides, fatty acids and carbohydrates · [8002-43-5]

Polymer, mixture or material of variable composition — no single molecular formula applies.

Surfactant, emulsifier

Typical concentrations: — · Dosage forms: Liquid, Sterile (parenteral/ophthalmic), Semi-solid

Used as a dispersing, emulsifying, wetting and stabilising agent in intramuscular and intravenous injections, parenteral nutrition fat emulsions, oral suspensions, topical creams and ointments, rectal and vaginal products, and as a suspending/dispersing agent and valve lubricant in metered-dose inhalers. Purified fractions are used to make liposomes. Typical concentrations: aerosol inhalation about 0.1%; intramuscular injection 0.3–2.3%; oral suspensions 0.25–10%. It is also widely used in foods and cosmetics.

Lecithins vary widely in appearance with their source, purity and free fatty acid content, from viscous semi-liquids to pastes and powders, and from brown to light yellow; highly refined grades are almost white. The odour ranges from almost none to faintly nut-like. Commercial material is obtained mainly from soybeans or egg yolk.

Acetone-insoluble matter

not less than 50% (USP-NF); purified fractions contain much more phosphatidylcholine

HLB

variable with composition; crude lecithin is in the lower (water-in-oil) range, and hydroxylated or enzyme-modified grades are more hydrophilic

Solubility

soluble in aliphatic and aromatic hydrocarbons, halogenated hydrocarbons, mineral oil and fatty acids; practically insoluble in cold vegetable and animal oils, polar solvents and water; disperses in water to form liposomes or emulsions

Lecithin is sensitive to oxidation of its unsaturated fatty acid chains and to hydrolysis, and it darkens on exposure to heat; liquid grades may separate on standing and powders are hygroscopic. Store in an airtight container, protected from light, at a cool temperature; purified grades are often stored refrigerated or under inert gas.

Incompatible with esterases, which hydrolyse it. Oxidising agents and extremes of pH accelerate its degradation.

Soybean lecithin is obtained as a by-product of soybean oil refining: the crude oil is degummed with water, and the hydrated phosphatides are separated and dried. Egg lecithin is extracted from egg yolk with solvents. Further fractionation with ethanol or acetone, and in some cases hydrogenation, gives purified phosphatidylcholine grades.

Phospholipids are normal components of cell membranes and of the diet, and lecithin is regarded as non-toxic. Rare hypersensitivity reactions may occur in people allergic to soy or egg because of residual proteins, and hypersensitivity has occasionally been reported with intravenous lipid emulsions.

Observe normal precautions for the quantity handled. Eye protection and gloves are recommended.

GRAS listed. Accepted as a food additive in Europe (E322); EFSA's re-evaluation found no need for a numerical ADI. Included in the FDA Inactive Ingredient Database (inhalation, intramuscular, intravenous, oral, rectal, topical and vaginal preparations) and in parenteral and non-parenteral medicines licensed in Europe.

Egg phospholipids; hydrogenated soybean phosphatidylcholine; phosphatidylcholine; synthetic phospholipids (for example dipalmitoylphosphatidylcholine).

Because 'lecithin' covers materials of very different composition, the grade (source, phosphatidylcholine content, degree of hydrogenation) must be specified for parenteral and liposomal products. Saturated (hydrogenated) phospholipids are much more resistant to oxidation than natural unsaturated grades.