Orotic acid, also known as orotate, is a pyrimidine derivative and a vitamin B-like compound. It plays a role in the synthesis of pyrimidine nucleotides in living organisms and exhibits unique chemical properties and physiological functions. Below is a detailed introduction:

I. Basic Properties

1. Chemical structure:

Molecular formula: C₅H₄N₂O₄

Molecular weight: 156.10

Its structure includes a pyrimidine ring, a carboxyl group (-COOH), and an amide group (-CONH-), making it a derivative of uracil (6-carboxyuracil).

2.Physical properties:

Appearance: White crystalline powder, odorless, with a slightly acidic taste.

Solubility: Slightly soluble in water (approx. 0.1 g/100 mL at 25°C); poorly soluble in ethanol and ether; easily soluble in dilute acids or bases due to the ionizable carboxyl group and acid/base reactivity of the amide group.

Melting point: Around 345–346°C (decomposes).

3.Chemical properties:

Exhibits general characteristics of carboxylic acids and can react with bases to form salts (e.g., sodium orotate, which has better water solubility).

The pyrimidine ring and amide group make it susceptible to hydrolysis or decomposition under high temperature or strong acid/base conditions.

Participates in enzymatic reactions in the body as a precursor in pyrimidine nucleotide biosynthesis.

II. Key Features

Unique biological activity: It is a key intermediate in the de novo synthesis pathway of pyrimidine nucleotides. In the liver, it is synthesized through multiple steps from precursors like aspartate and carbamoyl phosphate, eventually forming uridine monophosphate (UMP), which is essential for RNA, DNA, and coenzyme synthesis. It is vital for cell proliferation and metabolism.

Low toxicity and high safety: Naturally found in foods such as milk, animal liver, and yeast. It can also be synthesized endogenously in the human body. It is considered safe at normal dosages and has few side effects.

Metal ion coordination ability: The carboxyl and amide groups can form complexes with metal ions (e.g., Ca²⁺, Mg²⁺), affecting the absorption and metabolism of these ions—for example, by promoting calcium utilization.

Nutritional supplement potential: Although not strictly classified as a vitamin, it is often used as a nutritional fortifier, particularly in animal feed, to promote growth.

III. Applications

1. Pharmaceutical field:

Adjunctive treatment for liver diseases: Promotes liver cell regeneration and improves liver function, useful in the treatment of acute/chronic hepatitis and fatty liver.

Treatment of pyrimidine synthesis-related disorders: Used in conditions like orotic aciduria, a genetic disorder resulting in orotic acid accumulation due to enzyme deficiencies; supplementation helps regulate related metabolic pathways.

Nutritional supplement*: Supports cellular metabolism in patients undergoing chemotherapy or those with general weakness.

2. Feed industry:

A valuable feed additive, especially in poultry and aquaculture. It promotes growth, improves feed conversion rate, enhances immunity, and reduces the incidence of conditions like fatty liver. For instance, adding it to chick feed can help prevent growth retardation.

3. Food industry:

Used as a nutritional fortifier in functional foods to supply pyrimidine precursors. Suitable for individuals with high metabolic needs, such as athletes and the elderly.

4. Scientific research:

Serves as a biochemical reagent for studying the pyrimidine nucleotide biosynthesis pathway or as a nutrient component in cell culture media.

IV. Precautions

Orotic acid deficiency in humans is rare, but excessive intake may affect uric acid metabolism (thus, it should not be consumed alongside high-purine foods).

Its salts (e.g., sodium orotate) are more widely used in medicine and feed due to better water solubility.

Thanks to its central role in pyrimidine metabolism, orotic acid holds irreplaceable value in pharmaceutical and feed applications. Its safety and biocompatibility make it a vital functional compound.