Protocatechuic acid

Probably the most commonly referred to compound which accounts for a form of passive resistance of a chemical nature is protocatechuic acid (6.16) which is found in yellow and red skinned onions and prevents the germination of spores of the onion smudge fungus, Colletotrichum circinans. Thus, protocatechuic acid serves as a barrier to infection prior to penetration. Once penetration occurs the compound is ineffective. 

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On fusion with potash protocatechuic acid is formed. ... 

Studies by Hudson et al, (2000) have demonstrated the presence of eight polyphenols in rice bran by using high-pressure liquid chromatography. They are protocatechuic acid, p-coumaric acid, ferulic acid, sinapic aci vanillic acid, caffeic acid, which is a methoxycirmamic acid derivative, and tricin. The effect of these polyphenols on cell viability and on the colony-forming ability of human-derived MDA MB 468 and HBL 100 breast cells, colon-derived SW 480 and human colonic epithelial cells was assessed. These authors concluded that rice bran polyphenols have putative cancer chemopreventive properties. 

The total phenolic content in XRPP was 1.10%. The major components were found to be p-hydroxybenzoic acid (0.44%), vanillin (0.19%), syringic acid (0.13%), and syringaldehyde (0.13%). The contents of p-hydroybenzaldehyde, vanillic acid and ferulic acid were 0.032, 0.015 and 0.020%, respectively. Gallic acid, protocatechuic acid and cinnamic acid were detected in trace amounts. 

Iwagami S, K Yang, J Davies (2000) Characterization of the protocatechuate acid catabolic gene cluster from Streptomyces sp. strain 2065. Appl Environ Microbiol 66 1499-1508. 

Crawford RL (1975b) Novel pathway for degradation of protocatechuic acid in Bacillus species. J Bacteriol 121 531-536. 

Kampa et al. made the interesting observation that protocatechuic acid, which is found in grapes and red wine from Vitis vimfera (Vitaceae), showed a time- and dose-dependent inhibitory effect on cell growth of T47D human breast cancer cells at low concentrations (108). The phenolic compound is a potent inhibitor of topoisomerase I (109). The plant likely contains some germanacrolides because these sesquiterpenes are known... 

Piperonylic acid has been made by the oxidation of piperic acid,1 piperonal,1 safrole2 and isosafrole2 with potassium permanganate. It has also been prepared by the action of methylene iodide on protocatechuic acid 3 in the presence of alkali. 

Landete and others (2009) reported that Lactobacillus plantarum have the ability to metabolize phenolic compounds found in olive products (such as oleuropein, hydroxytyrosol, and tyrosol, as well as vanillic, p-hydroxybenzoic, sinapic, syringic, protocatechuic, and cinnamic acids). For example, oleuropein was metabolized mainly to hydroxytyrosol, whereas protocatechuic acid was decarboxylated to catechol by the enzymatic actions. 

Wang et al. (62) reported the oxidative polymerization of a mixture of phenolic compounds in aqueous solution containing mont-morillonlte, illite, and kaolinite, each of which had been mixed with quartz in a 3 7 ratio, and by quartz alone. The mixture of phenolic compounds contained gallic acid, pyrogallol, protocatechuic acid, caffeic acid, orcinol, ferulic acid, p-coumaric acid, syringic acid, vanillic acid, and p-hydroxybenzoic acid. The oxidative... 

Fig. 2.79. Chromatograms of a white (I) and red wine sample (II). (LC-DAD signals at three different wavelenghts 256, 324, 365 nm). Peak identification 1 = gallic acid 2 = protocatechuic acid 3 = p-hydroxybenzoic acid 4 = vanillic acid 5 = caffeic acid 6 = (+)-catechin 7 = syringic acid 8 = p-coumaric acid 9 = ( — )-epicatechin 10 = ferulic acid 11 = fraras-resveratrol 12 = rutin 13 = myricetin 14 = cw-resveratrol 15 = quercetin A = caftaric acid B = coutaric acid. Reprinted with permission from M. Castellari et al. [196],...

Biological. Benzoic acid may degrade to catechol if it is the central metabolite whereas, if protocatechuic acid (3,4-dihydroxybenzoic acid) is the central metabolite, the precursor is 3-hydroxybenzoic acid (Chapman, 1972). Other compounds identified following degradation of benzoic acid to catechol include cis,c/5-muconic acid, (+)-muconolactone, 3-oxoadipate enol lactone, and 3-oxoadipate (quoted, Verschueren, 1983). Pure microbial cultures hydroxylated benzoic acid to 3,4-dihydroxybenzoic acid, 2- and 4-hydroxybenzoic acid (Smith and Rosazza, 1974). In activated sludge, 65.5% mineralized to carbon dioxide after 5 d (Freitag et al., 1985). 

Biological. In anaerobic sludge, di-/3-butyl phthalate degraded as follows mono-/3-butyl phthalate to o-phthalic acid to protocatechuic acid followed by ring cleavage and mineralization. 

Biological. A proposed microbial degradation mechanism is as follows 4-hydroxy-3-methylbenzyl alcohol to 4-hydroxy-3-methylbenzaldehyde to 3-methyl-4-hydroxybenzoic acid to 4-hydroxyisophthalic acid to protocatechuic acid to p ketoadipic acid (Chapman, 1972). In anaerobic sludge, diethyl phthalate degraded as follows monoethyl phthalate to phthalic acid to protocatechuic acid followed by ring cleavage and mineralization (Shelton et al, 1984). 

The stepwise stability constants for V complexes with glutamic, aspartic, W -ethylenediaminedisuccinic, and W -ethylenediamine-bis-(a-glutaric acid) have been reported.The 1 1 oxovanadium(iv) complex of 5-nitrosalicylic acid has been characterized = 710 nm), and the mixed species formed between vanadium(iv) with protocatechuic acid (H3L ) or gallic acid (H L ) and 4-aminoantipyrine (aant) have been identified spectroscopically as the 1 1 1 and 1 2 2 HL (HL ) aant complexes. The species present in solutions of and tartaric acid below pH 2 have been identified as [VO-... 

Figure 3. Proposed biosynthetic pathways to gallic acid (5). (1) Dehy-droshikimic acid (2) caffeic acid (3) 3,4,5-trihydroxycinnamic acid (4) protocatechuic acid.

Phenolic acids Benzoic acid derivatives OH Caffeic acid 1 Gentisic acid Benzoic acid 1 1 Vanllic acid Protocatechuic acid 1 /7-Hydroxybenzoic acid COOH Syringic acid Hydroxy-isochromans HO. l-phenyh6,7- dihydroxy-isochroman l-(3 -methoxy-4- hydroxyphenyh6,7- dihydroxydsochroman R1... 

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