Protocatechuic acid structure

Borbulevych, O.Y. et al.. Lipoxygenase interactions with natural flavonoid, quercetin, reveal a complex with protocatechuic acid in its x-ray structure at 2.1 A resolution. Proteins, 54, 13, 2004. 

There is a substantial literature on the transformation of simple phenolic acids by microorganisms.2,7,11,16,18,20,22,25,29,44 For example, ferulic acid is transformed by fungi to either caffeic acid or vanillic acid, and these are transformed to protocatechuic acid. Next the ring structure of protocatechuic acid is broken to produce 3-carboxy-c/s,c/s-muconic acid, which is then converted to (3-oxoadipic acid (Fig. 3.1), which in turn is broken down to acetic acid and succinic acid, and these ultimately are broken down to C02 and water.11,18,29 Flowever, distribution of residual 14C-activity after growth of Hendersonula toruloidea, a fungus, in the presence of specifically 14C-labeled ferulic acid ranged from 32 to 45% in C02, 34 to 45% in cells, 9 to 20% in humic acid and 4 to 10% in fulvic acid.29 Thus, a considerable portion of the ferulic-acid carbon was bound/fixed over a 12-week period, and the initial ferulic acid transformation products (e.g., caffeic acid, vanillic acid and protocatechuic acid) were clearly of a transitory nature. Similar observations have also been made for other simple phenolic acids 22,23 however, the proportions metabolized to C02 and fixed into cells and the soil... 

V=9.267(1) nm, Z=4, Ri=0.0S3 and Rw=0,058. The complex is composed of copper cations, nitrate anions, 1,10-phenanthroline, protocatechuic acid and lattice water molecules. The structure of H3PCA, N03 and waters comprises packing of three-dimensional network by hydrogen bonds with cavities. The complex can be considered as a model of host/guest supermolecule. The three-dimensional hydrogen-bonding network is the host species. The Cu(phen)3 cations, guest species, occupy the cavities of the host. 

Scheme 1 Structural forms of protocatechuic acid and protocatechuates...

I). At the end of the 3-week incubation, there was a proportionate increase in the amount of 14C02 evolved and decrease in the soil-bound residues formed as the number of 2,4-dichlorophenol pretreatments increased (Table I). The potential of structurally similar compounds such as protocatechuic acid and vanillic acid in conditioning soils for rapid degradation of 2,4-D has been documented (23). 

Simple benzoic acids are synthesized in plants via the shikimate pathway, which is derived from shikimic acid, which is itself derived from quinic acid via 3-dehydroquinic and 3-dehydroshikimic acids (Scheme 68.1). In fact, shikimic, but not quinic, acid has been described in the leaves and stems of this species [14]. The simplest benzoic acids are protocatechuic acid (3,4-dihydroxybenzoic acid) and gallic acid (3,4,5-trihydroxybenzoic acid). The latter proved to be present in the tissues of C. roseus, in addition to vanillic acid (4-hydroxy-3-methoxybenzoic acid) [15]. The quantitative composition of C. roseus in benzoic acids can be seen in Table 68.1, and the structures of these compounds are represented in Fig. 68.1. 

Depending on food source, anthocyanins can be chemically different, mainly as glucosides or rutinosides. However, the stmcture of the metabolites is not dependent on sugar moieties naturally attached to polyphenol but on the structural characteristics of the polyphenol. Protocatechuic acid is the main metabolite detected after anthocyanin consumption [79, 81, 84]. 

Utilization of phenolic acids by microbes can be substantial as long as conditions are appropriate, e.g., adequate nutrition, moisture, pH, and temperature. However, a variety of other factors can also influence microbial utilization of phenolic acids. For example, phenolic acid utilization by microbes was reduced when more readily available carbon sources were present in the soil such as glucose and phenylalanine (Fig. 2.24 Blum et al. 1993 Pue et al. 1995) or other sources of available carbon, i.e., roots (Blum et al. 1999a). The presence of methionine, however, did not influence the rate of phenolic acid utilization by soil microbes (Pue et al. 1995). Differential utilization of carbon sources by soil microbes is fairly common (Martin and Haider 1979 Harder and Dijkhuizen 1982 Papanastasiou 1982 Sugi and Schimel 1993). Thus the relationship between phenolic acid-utilizing microbes and their carbon environment is complex. There is yet another aspect that adds to this complexity. Initial microbial breakdown products of phenolic acids are frequently other phenolic acids. For example, ferulic acid is converted to caffeic acid or vanillic acid and these are converted to protocatechuic acid. Next the ring structure of the... 

Zhang ZY, Han PF, Liang MD, Rao MR 1980 Experimental studies on relationship of chemical structure of protocatechuic acid derivatives and cardiac oxygen consumption and coronary flow. Yao Hsueh Hsueh Pao 15 641-647... 

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