homogentisic acid

1. Homogentisic acid (2,5-dihydroxyphenylacetic acid) shows interesting antioxidant and antiradical activities, and protective effect against thermal-cholesterol degradation, comparable to those of well known antioxidants. 2. Homogentisic acid is the primary precursor of melanin synthesis in Vibrio cholerae, a Hyphomonas strain, and Shewanella colwelliana. 3. A derivative of homogentisic acid which inhibits Pfnek-1 with an IC(5) around 1.8 muM, this product is moderately active in vitro against a FcB1 P. falciparum strain (IC(5) = 12 muM).

Homogentisic acid lactone (Compound 1) is a fungal metabolite with antifungal properties, identified in the fungus WF5. It exhibits inhibitory effects against the plant pathogen F. graminearum. Additionally, homogentisic acid lactone can serve as a substrate for measuring serum paraoxonase aromatic esterase 1 (PON1) activity.

Phaseoloidin, a homogentisic acid glucoside from Nicotiana attenuata trichomes, contributes to the plant's resistance against lepidopteran herbivores.

4-Hydroxyphenylpyruvic acid is an enzyme inhibitor.4-Hydroxyphenylpyruvic acid (4-HPPA) is a keto acid that is involved in the tyrosine catabolism pathway. It is a product of the enzyme (R)-4-hydroxyphenyllactate dehydrogenase (EC 1.1.1.222) and is formed during tyrosine metabolism. The conversion from tyrosine to 4-HPPA is catalyzed by tyrosine aminotransferase. Additionally, 4-HPPA can be converted to homogentisic acid which is one of the precursors to ochronotic pigment. The enzyme 4-hydroxyphenylpyruvic acid dioxygenase (HPD) catalyzes the reaction that converts 4-hydroxyphenylpyruvic acid to homogentisic acid. A deficiency in the catalytic activity of HPD is known to lead to tyrosinemia type III, an autosomal recessive disorder characterized by elevated levels of blood tyrosine and massive excretion of tyrosine derivatives into urine. It has been shown that hawkinsinuria, an autosomal dominant disorder characterized by the excretion of 'hawkinsin,' may also be a result of HPD deficiency . Moreover, 4-hydroxyphenylpyruvic acid is also found to be associated in phenylketonuria, which is also an inborn error of metabolism. There are two isomers of HPPA, specifically 4HPPA and 3HPPA, of which 4HPPA is the most common.