The content and distribution of condensed tannins in different species of the genus sorghum (Sorghum Moench) and their effect on seed protein electrophoresis

Abstract

AbstractBACKGROUND: The interaction between condensed tannins (CTs) and seed protein in varieties of sorghum interferes with protein extraction and the separation by electrophoresis, so electrophoresis can not be used widely for determining seed purity and identifying a variety. The objective of this research was to classify the effect of CTs on the extraction of seed storage proteins and on their analysis by SDS–PAGE, and to search for a promising solution to reduce the negative effect of CTs in sorghum.RESULTS: The vanillin–HCl test confirmed that CTs were localised mainly in the glumes of grain sorghum, but distributed in every fraction of sudangrass. Samples with high CT content did not produce any bands in the gel after electrophoresis. Removal of the glumes and pericarp/testa prevented the influence of CTs on electrophoresis for grain sorghum but had little effect for sudangrass. Adding tannin/catechin to the protein extraction of sorghum kernel decreased the number of bands in the gel. Adding polyvinylpyrrolidine to the protein extraction of sudangrass increased the bands.CONCLUSION: Tannin–protein interactions are responsible for the absence of bands in varieties with high CT content. For grain sorghum, decortication can prevent the influence. Adding polyvinylpyrrolidine during the extraction of seed protein could solve the problem of tannin–protein interactions for varieties of sudangrass. Copyright © 2009 Society of Chemical Industry