Canadian Forest Service Publications
An improved butanol-HCl assay for quantification of water-soluble, acetone:methanol-soluble, and insoluble proanthocyanidins (condensed tannins). 2017. Shay, P-E., Trofymow, J.A., Constabel, C.P. Plant Methods, 13: 63.
Issued by: Pacific Forestry Centre
Catalog ID: 38869
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Condensed tannins (CT) are the most abundant secondary metabolite of land plants and can vary in abundance and structure according to tissue type, species, genotype, age, and environmental conditions. Recent improvements to the butanol-HCl assay have separately helped quantification of soluble and insoluble CTs, but have not yet been applied jointly. Our objectives were to combine previous assay improvements to allow for quantitative comparisons of different condensed tannin forms and to test protocols for analyses of condensed tannins in vegetative plant tissues. We also tested if the improved butanol-HCl assay can be used to quantify water-soluble forms of condensed tannins.
Plain Language Summary
Condensed tannins are among the most abundant secondary compounds produced by plants and can affect insects feeding and fungal diseases on live plant tissues and decay by microbes of dead plant tissues. However, methods to accurately measure amounts of tannins in plant tissues remains difficult, since tannins occur in different forms that can affect their biological activity. Few studies examined what these forms are and how to quantify them. In this paper, improvements to a standard method for measuring condensed tannins, the butanol-HCl assay, are described and tested. The new method allows for the measurement of three different tannin forms in plant tissue based on their solubility in different solvents ie. water-soluble, acetone:methanol-soluble, and insoluble. The three different forms of tannins were measured in natural poplar leaf and Douglas-fir needle litter fall, as well as in a variety of fresh poplar tissues including roots. We show how our assay methods for the three biologically relevant forms is highly replicable and describe potential pitfalls researchers can avoid when using this assay on different plant tissue types.