Pyrroloquinoline quinone (PQQ) is an aromatic ortho-quinone compound and also a coenzyme of oxidoreductases, known as "the 14th vitamin". It possesses a unique redox cycling capability, allowing reversible conversion between oxidized and reduced forms, and participates in electron transfer and various metabolic reactions in organisms. PQQ is widely found in fruits, vegetables, cereals and fermented foods, and is one of the essential nutrients for mammals.

1. Food and nutritional supplements: As a novel food ingredient, it is used in functional foods and dietary supplements, with effects such as anti-oxidation, mitochondrial function promotion, and neuroprotection.

2. Pharmaceutical field: Used in the research and development of drugs related to anti-oxidation, anti-inflammation, anti-hepatic fibrosis, neuroprotection and anti-pigmentation.

3. Biochemical engineering: As a coenzyme of oxidoreductases, it is used in microbial fermentation, gluconic acid production and biocatalytic reactions.

4. Cosmetics: Used as a skin conditioning agent, humectant and antioxidant, added in anti-aging and repairing skin care products.

5. Agriculture: As a plant growth promoter and biological control factor, it improves crop stress resistance and yield.