Biosynthesis of gallic acid

Comparatively little is yet known concerning the biosynthesis of the various derivatives of gallic acid, such as the esters and depsides that occur in plants. Biogenetic relationships have been proposed to link these groups of substances 

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The biosynthesis of gallic acid (3.47) has been under investigation for more than 50 years. Different biosynthetic routes have been proposed, as depicted in Figure 3-6 (/) direct biosynthesis from an intermediate of the shikimate pathway, (2) biosynthesis via phenylalanine (3.27), cinnamic acid (3.29), />coumaric acid (3.30), caffeic acid (3.32), and 3,4, 5-trihydroxycinnamic acid (3.44), or (3) biosynthesis via caffeic acid (3.32) and protocatechuic acid (3.45). The possibility that different pathways co-existed in different species or even within one species was also considered. 

Wemer, R. A., Rossmann, A., Schwarz, C., Bacher, A., Schmidt, H.-L., and Eisenreich, W., 2004, Biosynthesis of gallic acid in Rhus typhina discrimination between alternative pathways from natural oxygen isotope abundance, Phytochem. 65 2809-2813. 

Conn, E. E. and T. Swain, Biosynthesis of gallic acid in higher plants, Chem. Ind., 592-593 (1961). 

Against this backcloth it is perhaps not surprising to learn, that, despite its distinctive position in the overall patterns of plant phenol metabolism, ambiguity still surrounds the biosynthesis of gallic acid. Several pathways have been proposed. Zenk formulated a conventional pathway (Fig. 7, a) from L-phenylalanine to 3,4,5-trihydroxy-cinnamic acid followed by 6-oxidation to give gallic acid. 

Cornthwaite D C,Haslam E 1965 Gallotannins. Part 9. The biosynthesis of gallic acid in Rhus typhina. J Chem Soc 3008-3011... 

Knowles P F, Haworth R D, Haslam E 1961 Gallotannins. Part 4. The biosynthesis of gallic acid. J Chem Soc 1854-1859... 

CoRNTHWAiTE, D. C., and E. Haslam Gallotannins Part 9. The Biosynthesis of Gallic acid in Rhus typhina. J. Chem. Soc. 1965, 3008. 

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