Prolamin extraction from high polyphenol seeds of sorghum (Sorghum spp.) and species discrimination and varieties identification by ultrathin-layer isoelectric focusing

Abstract

The seeds of sorghum (Sorghum spp.) are rich in polyphenols, which cause protein precipitation and coloration of extracts. Because of this precipitation, proteins in seeds of sorghum cannot be effectively extracted using common methods. Here we report two modified methods for the seed protein extraction. The result showed that the method in which the samples were pretreated by polyvinylpyrrolidone (PVPP) before protein extraction (modified method 2) got more prolamine content and can be used for later ultrathin layer isoelectric focusing electrophoresis (UTLIEF) analysis. Seed prolamin variation between two sorghum (Sorghum spp.) species included twelve sorghum varieties and eight sudangrass varieties were analyzed by UTLIEF. The result showed that obvious polymorphisms within and among varieties can be revealed through electrophoresis of sorghum single seed sample. Meanwhile, polymorphisms within species and varieties are concealed when sample was bulk which contains more than 100 seeds. By means of visual evaluation of the presence or absence of the special region bands of electrophogram, sorghum and sudangrass can be discriminated from each other. Furthermore, 10 of 12 sorghum varieties or lines and six of eight sudangrass varieties can be identified successfully according to the unique banding patterns in the discriminated regions which Rf was 0.314 to 0.332 and 0.605 to 0.826, respectively. Key word: Sorghum, species discrimination, variety identification, ultrathin layer isoelectric focusing electrophoresis.