Leucine

• BPLeucine
• JPL-Leucine
• Ph. Eur.Leucine
• USP–NFLeucine

L-Leucine; (S)-2-amino-4-methylpentanoic acid; α-aminoisocaproic acid; leucinum

(S)-2-Amino-4-methylpentanoic acid · [61-90-5]

UNII GMW67QNF9C · PubChem CID 6106

C6H13NO2 · 131.17

Lubricant

Typical concentrations: — · Dosage forms: Solid

Leucine is used as a water-soluble lubricant in tablets, particularly effervescent and soluble tablets where insoluble stearates would leave a scum. In spray-dried powders for inhalation it is added as a dispersibility enhancer: it accumulates at the particle surface, lowering cohesion and moisture uptake and improving aerosol performance; levels of several percent up to about 20% w/w are commonly reported. It is also used as a nutritional amino acid.

White, shiny crystals or white crystalline powder, practically odourless, with a slightly bitter taste. It is an essential, branched-chain amino acid.

Melting point

sublimes and decomposes at about 290–295 °C

Solubility

sparingly soluble in water; practically insoluble in ethanol (95%); dissolves in dilute mineral acids and dilute alkali hydroxide solutions

pKa

≈ 2.4 (carboxyl); ≈ 9.6 (amino)

Isoelectric point

≈ 6.0

pH

about 5.5–6.5 (1% w/v aqueous solution)

Stable under normal storage conditions. Store in a well-closed container, protected from light, in a cool, dry place.

Incompatible with strong oxidising agents. As a primary amine it can take part in Maillard reactions with reducing sugars.

Produced mainly by microbial fermentation followed by isolation and purification; it can also be obtained by hydrolysis of proteins.

A normal dietary component and regarded as non-toxic and non-irritant at the levels used as an excipient.

Observe normal precautions for the quantity handled. Avoid generating dust; eye protection, gloves and a dust mask are recommended.

Permitted in the USA as a nutrient food additive (21 CFR 172.320). Monographs exist in the major pharmacopoeias.

Isoleucine; valine; glycine; sodium benzoate (as an alternative soluble lubricant).

As a tablet lubricant leucine is less efficient than magnesium stearate, so relatively high levels are needed, but it gives clear solutions. In spray drying, its low aqueous solubility makes it precipitate early at the droplet surface, which is the basis of its shell-forming effect; the crystallinity of the surface layer depends on drying conditions.