Tannin biosynthesis

Brown, S. A., Lignin and tannin biosynthesis, in Biochemistry of Phenolic Compounds, Harborne, J. B., Ed., Academic Press, London, 1964, 387. 

Carron, T.R., Robbins, M.P., and Morris, P., Genetic modification of condensed tannin biosynthesis in Lotus corniculatus. 1. Heterologous antisense dihydroflavonol reductase down-regulates tannin accumulation in hairy root cultures. Theor. Appl. Genet., 87, 153, 1994. 

Phenolic compounds and flavonoids are a unique category of plant phytochemicals especially in terms of their vast po ential health-benefiting properties. They represent the most abundant and the most widely represented class of plant natural products. A substantial amount of research has been carried out over the past two decades yet large information gaps still exist. For example, the inventory of these compounds is still incomplete, although there is continuous effort to provide new structures. In addition the dissection of the metabolic pathways for certain phenolic compounds remains to be resolved. Recent reports underline that important questions that still need to be answered in the field of proanthocyanidin and tannin biosynthesis [Xie and Dixon, 2005], and even the exact nature of the biosynthetic pathway(s) leading to lignin monomers is not fully elucidated. 

Takos AM, Ubi BE, Robinson S, Walker AR. 2006b. Condensed tannin biosynthesis genes are regulated separately from other flavonoid biosynthesis genes in apple fruit skin. Plant Sci 170 487 -99. 

ARNOLD, T.M., SCHULTZ, J.C., Induced sink strength as a prerequisite for induced tannin biosynthesis in developing leaves of Populus, Oecologia, 2002,130, 585-593. 

Jiro. The method for the extraction of insoluble tannins from the fruits of nonastringent (PCNA) persimmon needs improvement, if tannin biosynthesis during fruit development is to be studied further. 

Mehansho, H., Hagerman, A., Clements, S., etal. (1983). Modulation of proline-rich protein biosynthesis in rat parotid glands by sorghums with high tannin levels. Proceedings ofthe National Academy of Sciences USA 80, 3948-3952. 

As documented in a review article (9), no experimental data was available to support hypothetical mechanisms for the biosynthesis of hydrolyzable tannins until recently. Enzymatic studies have now changed this unsatisfactory situation, at least as far as the formation of pentagalloylglucose is concerned. Future work will provide insight into those other challenges discussed in this contribution and that still require clarification. 

The PAs, or condensed tannins, are polymers synthesized from flavan-3-ol monomer units. The phlobaphenes are 3-deoxy-PAs formed from flavan-4-ol monomers. The biosynthesis of both types of PAs follows the biosynthetic route of anthocyanins from chalcones through to the branch points to flavan-3-ol and flavan-4-ol formation. In this section, the specific enzymes forming the monomers are discussed, along with a discussion on the polymerization process. Although the chemistry of tannins is described in detail elsewhere in this book, it is useful to briefly mention the nature of the monomer subunit types and the polymer forms. 

Figure 3-8. Biosynthesis of anthocyanins and condensed tannins. The enzymes involved in this pathway are (a) anthocyanidin synthase (E.C. 1.14.11.19), (b) anthocyanin 3-glycosyl transferase, and (c) BANYULS.

Stafford HA. 1989. The cnzymology of proanthocyanidin biosynthesis. In Hemingway RW, Karchesy JJ, Eds. Chemistry and Significance of Condensed Tannins. New York Plenum Press, pp. 345-368. 

Gross GG (1999) Biosynthesis of hydrolyzable tannins. Comprehensive Natural Products Chemistry, Vol 3. Elsevier, Amsterdam, pp 799-826. 

Grundhofer, R, Niemetz, R., Schilling, G. and Gross, G.G. (2001) Biosynthesis and subcellular distribution of hydrolysable tannins. Phytochemistry, 57, 915-27. 

Mohnen D (1999) Biosynthesis of pectins and galactomannans. In Pinto BM (ed) Carbohydrates and their derivatives including tannins, cellulose, and related lignins, vol 3, Comprehensive natural products chemistry. Elsevier, Amsterdam, chap 3.15... 

Bugg TDH (1999) Bacterial Peptidoglycan. Biosynthesis and its Inhibition. In Pinto BM (ed) Carbohydrates and Their Derivatives Including Tannins, Cellulose, and Related Lignins (Comprehensive Natural Products Chemistry, vol 3). Elsevier, Amsterdam, p241... 

Biosynthesis of Flavan-3-ols (40) and Condensed Tannins (Proanthocyanidins, 44) from Leucoanthocyanidins (Flavan-3,4-diols, 37)... 

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