Isolation, purification and characterization of proteinaceous fungal α-amylase inhibitor from rhizome of Cheilocostus speciosus (J.Koenig) C.D.Specht

As the aim of this present study, a proteinaceous α-amylase inhibitor has been isolated from the rhizome of Cheilocostus specious (C. speciosus) and was purified using DEAE cellulose anion exchange chromatography followed by gel filtration using Sephacryl-S-200 column. The purity and molecular mass of the purified inhibitor was determined by SDS-PAGE and LC-MS respectively. The molecular mass of the purified inhibitor was determined to be 31.18 kDa. Protein-protein docking was also carried out as molecular model. Model validation methods such as Ramachandran plot and Z-score plot were adopted to validate the structural description (sequence analysis) of proteins. The inhibitory activity was confirmed using spectrophotometric and reverse zymogram analyses. This 31.18 kDa protein from C. speciosus inhibited the activity of fungal α-amylase by 71% at the level of ion exchange chromatography and 96% after gel filtration. The inhibition activity of the α-amylase inhibitor was stable and high at optimum pH 6 (52.2%) and temperatures of 30-40 °C (72.2%). Thus it was suggested that the main responsible for the versatile biological and pharmacological activities of C. speciosus is due to its primary metabolites (proteins) only.