Urea (Carbonyldiamide) is formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end metabolite of protein catabolism and accounts for about one-half of the total urinary solids.

Pygmaniline B (1,3-bis(2,4-dimethoxyphenyl)urea) is a marine derived natural products found in Lichina pygmaea.

1,3-Diphenethylurea (N,N'-Bis(phenethyl)urea) is a marine derived natural products found in Lissoclinum patella.

Allantoin (Glyoxyldiureide), a urea hydantoin found in urine and plants, is used in dermatological preparations.

Benzoyleneurea has anti-bacterial activity.

Virgaureagenin F, a saponin, is derived from the rhizome of Bolbostemma [1].

Orotic acid zinc (Zinc Orotate) salt dihydrate is an intermediate product in pyrimidine synthesis.

Purpureaside C is a phenolic glycoside with significant proinflammatory, immunomodulating and antimicrobial effects.

Benzylurea (AI3-61350) competitively inhibits dehydrogenase/cytokinin oxidase.

N,N'-Dimethylthiourea (DMTU) (DMTU), isolated from Allii Sativi Bulbus, is an orally active scavenger of hydroxyl radical ( OH) and blocks OH production by activated neutrophils in vitro. N,N'-Dimethylthiourea protects against water-immersion restraint stress (WIRS)-induced gastric mucosal lesions in rats by exerting its antioxidant action including OH scavenging and anti-inflammatory action [1][2] .

Orotic acid (Vitamin B13) is an intermediate product in pyrimidine metabolism.

4-Acetamidobutanoic acid (4-ACETAMIDOBUTYRIC ACID) can be found in blood, feces, and urine, as well as in human prostate tissue. 4-Acetamidobutanoic acid exists in all eukaryotes, ranging from yeast to humans. 4-Acetamidobutanoic acid is a GABA derivative, a product of the urea cycle and the metabolism of amino groups, and the product of NAD-linked aldehyde dehydrogenase (EC 1.2.1.3) (KEGG).

L-Homocitrulline (Homocitrulline) is a metabolite that can be detected in larger amounts in the urine of individuals with urea cycle disorders. The accumulation of carbamyl phosphate due to a depleted supply of ornithine for the urea cycle may be responsible for the enhanced synthesis of L-Homocitrulline and homoarginine in some cases.

Phloretin (NSC-407292) is a well-known inhibitor of eukaryotic urea transporters, blocks VacA-mediated urea and ion transport. Phloretin is a dihydrochalcone, a type of natural phenols. It can be found in apple tree leaves and the Manchurian apricot. It promotes potent antioxidative activities in peroxynitrite scavenging and the inhibition of lipid peroxidation. It has been found to inhibit the growth of several cancer cells and induce apoptosis of B16 melanoma and HL60 human leukemia cells.

L-Ornithine hydrochloride ((S)-2,5-Diaminopentanoic acid) has an antifatigue effect by increasing the efficiency of energy consumption and promoting the excretion of ammonia. It is one of the key reactants in the urea cycle.

Ureidopropionic acid (3-Ureidopropionic acid) is an intermediate in the metabolism of uracil. More specifically it is a breakdown product of dihydrouracil and is produced by the enzyme dihydropyrimidase. It is further decomposed to beta-alanine via the enzyme beta-ureidopropionase. Ureidopropionic acid is essentially a urea derivative of beta-alanine. High levels of Ureidopropionic acid are found in individuals with beta-ureidopropionase (UP) deficiency. Enzyme deficiencies in pyrimidine metabolism are associated with a risk for severe toxicity against the antineoplastic agent 5-fluorouracil.

N-Acetyl-L-glutamic acid (Ac-L-Glu-OH) (NAcGlu) is an acetylated amino acid. NAcGlu is biosynthesized from glutamic acid and acetyl-CoA by the enzyme N-acetyl glutamate synthase (NAGS). NAcGlu activates carbamoyl phosphate synthetase in the urea cycle. A deficiency in N-acetyl glutamate synthase or a genetic mutation in the gene coding for the enzyme will lead to urea cycle failure in which ammonia is not converted to urea, but rather accumulated in the blood leading to the condition called Type I hyperammonemia.

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.

Trimethylamine N-oxide dihydrate (TMANO Dihydrate), a product of the oxidation of trimethylamine, is considered as a protein stabilizer that may serve to counteract urea, the major osmolyte of sharks, skates and rays.

2-Amino-5-ureidopentanoic acid (Citrulline) exists in the liver, is not a protein component, is an important intermediate in the human urea cycle, can be combined with ornithine, arginine to treat hyperammonemia.