Leucine (abbreviated as Leu or L) is a branched-chain α-amino acid with the chemical formula HO2CCH(NH2)CH2CH(CH3)2. Leucine is classified as a hydrophobic amino acid due to its aliphatic isobutyl side chain. It is encoded by six codons (UUA, UUG, CUU, CUC, CUA, and CUG) and is a major component of the subunits in ferritin, astacin and other 'buffer' proteins. Leucine is an essential amino acid, meaning that the human body cannot synthesize it, and it, therefore, must be ingested.
| Item | Index |
| Specific rotatory power[α] D20 | +14.9º 16º |
| Clarity | >=98.0% |
| Chloride[CL] | =<0.02% |
| Sulfate[SO4] | =<0.02% |
| Residue on ignition | =<0.10% |
| Iron salt[Fe] | =<10 ppm |
| Heavy metal[Pb] | =<10 ppm |
| Arsenic salt | =<1 ppm |
| Ammonium salt[NH4] | =<0.02% |
| Other amino acid | =<0.20% |
| Loss on drying | =<0.20% |
| Content | 98.5 100.5% |