|Molar mass||154.12 g/mol|
|Appearance||light brown solid|
|Melting point||221 °C (430 °F; 494 K) (decomposes)|
|1.24 g/100 mL|
|Solubility||soluble in ethanol, ether
insoluble in benzene
|Acidity (pKa)||4.48 |
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Protocatechuic acid (PCA) is a dihydroxybenzoic acid, a type of phenolic acid. It is a major metabolite of antioxidant polyphenols found in green tea. It has mixed effects on normal and cancer cells in in vitro and in vivo studies.
Protocatechuic acid (PCA) is antioxidant and anti-inflammatory. PCA extracted from Hibiscus sabdariffa protected against chemically induced liver toxicity in vivo. In vitro testing documented antioxidant and anti-inflammatory activity of PCA, while liver protection in vivo was measured by chemical markers and histological assessment.
PCA has been reported to induce apoptosis of human leukemia cells, as well as malignant HSG1 cells taken from human oral cavities, but PCA was found to have mixed effects on TPA-induced mouse skin tumours. Depending on the amount of PCA and the time before application, PCA could reduce or enhance tumour growth. Similarly, PCA was reported to increase proliferation and inhibit apoptosis of neural stem cells. In an in vitro model using HL-60leukemia cells, protocatechuic acid showed an antigenotoxic effect and tumoricidal activity.
Occurrence in nature
The hardening of the protein component of insect cuticle has been shown to be due to the tanning action of an agent produced by oxidation of a phenolic substance. In the analogous hardening of the cockroach ootheca, the phenolic substance concerned is protocatechuic acid.
Açaí oil, obtained from the fruit of the açaí palm (Euterpe oleracea), is rich in protocatechuic acid (630 ± 36 mg/kg)., Protocatechuic acid also exists in the skins of some strains of onion as an antifungal mechanism, increasing endogenous resistance against smudge fungus. It is also found in Allium cepa (17,540 ppm).
- Biosynthesis enzymes
- 3-dehydroshikimate dehydratase
- (3S,4R)-3,4-dihydroxycyclohexa-1,5-diene-1,4-dicarboxylate dehydrogenase
- Terephthalate 1,2-cis-dihydrodiol dehydrogenase
- 3-hydroxybenzoate 4-monooxygenase
- 4-hydroxybenzoate 3-monooxygenase (NAD(P)H)
- 4-sulfobenzoate 3,4-dioxygenase
- Vanillate monooxygenase
- 3,4-dihydroxyphthalate decarboxylase
- 4,5-dihydroxyphthalate decarboxylase
- Degradation enzymes
The enzyme protocatechuate decarboxylase uses 3,4-dihydroxybenzoate to produce catechol and CO2.
The enzyme protocatechuate 3,4-dioxygenase uses 3,4-dihydroxybenzoate and O2 to produce 3-carboxy-cis,cis-muconate.
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- Liu, CL; Wang, JM; Chu, CY; Cheng, MT; Tseng, TH (2002). "In vivo protective effect of protocatechuic acid on tert-butyl hydroperoxide-induced rat hepatotoxicity". Food Chem Toxicol 40 (5): 635–41. doi:10.1016/s0278-6915(02)00002-9. PMID 11955669.
- Babich H, Sedletcaia A, Kenigsberg B (November 2002). "In vitro cytotoxicity of protocatechuic acid to cultured human cells from oral tissue: involvement in oxidative stress". Pharmacol. Toxicol. 91 (5): 245–253. doi:10.1034/j.1600-0773.2002.910505.x. PMID 12570031.
- Nakamura Y, Torikai K, Ohto Y, Murakami A, Tanaka T, Ohigashi H (October 2000). "A simple phenolic antioxidant protocatechuic acid enhances tumor promotion and oxidative stress in female ICR mouse skin: dose-and timing-dependent enhancement and involvement of bioactivation by tyrosinase". Carcinogenesis 21 (10): 1899–1907. doi:10.1093/carcin/21.10.1899. PMID 11023549.
- Guan S, Ge D, Liu TQ, Ma XH, Cui ZF (March 2009). "Protocatechuic acid promotes cell proliferation and reduces basal apoptosis in cultured neural stem cells". Toxicology in vitro : an international journal published in association with BIBRA 23 (2): 201–208. doi:10.1016/j.tiv.2008.11.008. PMID 19095056.
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- Pietta, P. G.; Simonetti, P.; Gardana, C.; Brusamolino, A.; Morazzoni, P.; Bombardelli, E. (1998). "Catechin metabolites after intake of green tea infusions". BioFactors 8 (1-2): 111–118. doi:10.1002/biof.5520080119. PMID 9699018.