L-Isoleucine (Ile) is an essential branched-chain aliphatic amino acid found in many proteins. It is an isomer of LEUCINE. It is important in hemoglobin synthesis and regulation of blood sugar and energy levels.

(2S,3R,4S)-4-Hydroxyisoleucine (Hydroxyisoleucine) from fenugreek (Trigonella foenum-graecum) seeds is a potential insulinotropic (anti-diabetic) and anti-obesity amino acid. HIL stimulates glucose-dependent insulin secretion from pancreatic cells. HIL activates insulin receptor substrate-associated phosphoinositide 3 (PI3) kinase activity. HIL reduces plasma levels of triglycerides, free fatty acids and cholesterol.

L-Alloisoleucine (L-allo-Isoleucine) is a branched chain amino acid and is a stereoisomer of L-isoleucine. It is a common constituent of human plasma (albeit at low levels). L-alloisoleucine is produced as a byproduct of isoleucine transamination. Plasma L-alloisoleucine, which is derived from L-isoleucine in vivo, can be used for the diagnosis of maple syrup urine disease (MSUD), a genetic disorder. Indeed, plasma L-alloisoleucine levels above 5 μmol/L is the most specific and most sensitive diagnostic marker for all forms of MSUD.

D-Isoleucine ((2R,3R)-2-Amino-3-methylpentanoic acid) is a selective activator of Asc-1 antiporter, which enhances long-term potentiation at the hippocampal CA1-CA3 via release of endogenous D-serine.

4-Hydroxyisoleucine (4-Hydroxy-L-isoleucine) has antidepressant-like, antidyslipidemic, and antihyperglycemic effects. It displays an insulinotropic activity.

Methyl acetylacetate (Methyl acetoacetate) has been identified in the urine of patients with an inherited deficiency of propionyl-CoA carboxylase, and after isoleucine loading in the diagnosis of 2-methylacetoacetyl-CoA thiolase deficiency.

Kirromycin is an antibiotic originally isolated from Streptomyces and an inhibitor of protein biosynthesis. It inhibits isoleucine incorporation, polyphenylalanine synthesis, and growth of B. brevis. Kirromycin inhibits elongation factor Tu-dependent peptidyl transfer activity in E. coli.

L-Aspartic acid (Aspatofort) is a non-essential amino acid in humans, L-Aspartic acid has an overall negative charge and plays an important role in the synthesis of other amino acids and in the citric acid and urea cycles. Asparagine, arginine, lysine, methionine, isoleucine, and some nucleotides are synthesized from aspartic acid. L-Aspartic acid also serves as a neurotransmitter.

H-Abu-OH (L-α-amino-n-Butyric acid) , also known as (S)-2-aminobutanoic acid, homoalanine, 2-AABA, ethylglycine, or L-butyrine, is a member of the class of compounds known as L-alpha-amino acids. H-Abu-OH is a non-proteogenic amino acid that can be found in the human kidney, in liver tissues, and in most biofluids or excreta (e.g. feces, breast milk, urine, and blood). Within the cell, H-Abu-OH is primarily located in the cytoplasm. H-Abu-OH is biosynthesized by transaminating oxobutyrate, a metabolite in isoleucine biosynthesis. As a non-proteogenic amino acid, H-Abu-OH can be used by nonribosomal peptide synthases.