Gallotannins biosynthesis

Frohlich, B., Niemetz, R. and Gross, G.G. (2002) Gallotannin biosynthesis two new galloyltransferases from Rhus typhina leaves preferentially acylating hexa- and hep-tagalloylglucoses. Planta, 216, 168-72. 

Niemetz R, Gross GG (2005), Enzymology of gallotannin and ellagitannin biosynthesis , Phytochemistry, 66, 2001-2011. 

In enzymatic studies with cell-free extracts from higher plants, however, no evidence has been found to date for galloyl-CoA s involvement in the biosynthesis of / -glucogallin, or its higher galloylated derivatives an eventual role in the formation of the chemically different meta-depside bonds of gallotannins has not been investigated. 

Little knowledge also exists on the mechanisms involved in the biosynthesis of the characteristic structures of gallotannins and ellagitannins, as will be briefly discussed below. 

Hofmann, A. S., and Gross, G. G., 1990, Biosynthesis of gallotannins formation of polygalloylglucoses by enzymatic acylation of 1,2,3,4, 6-penta-O-galloylglucose, Arch. Biochem. Biophys. 283 530-532. 

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... 

Flavan-3-ols and Flavan-3,4-diols are the precursors of the second large group of tannins. They polymerize to the so-called condensed tannins. We have already mentioned the first group of tannins, the gallotannins. Flavan-3-ols are better known under the name catechins (Fig. 106). They are widely distributed in the plant kingdom. The same is true of the flavan-3,4-diols, which belong to the so-called leuco anthocyanins. This is because flavan-3,4-diols can be very easily converted into anthocyanins by boiling with alcoholic hydrochloric acid. However, this conversion does not play any role in the biosynthesis of the anthocyanins. 

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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