Partial purification of trypsin inhibitors from Caesalpinia ferrea and Swartzia polyphylla seeds and effect of protein extracts on pathogenic fungi

Abstract

Legume seeds present high concentration of trypsin inhibitors; these proteins are involved in both cell metabolism and plant defense mechanisms. In order to confirm or not a possible fungicidal action of these proteins from extracts of seeds of legume tree species, the aim this study was to detect trypsin inhibitors in seeds of Caesalpinia ferrea (CfTI) and Swartzia polyphylla (SpTI) and to test their extracts against the pathogenic fungi Colletotrichum guaranicola, Corynespora cassiicola, Fusarium oxysporum and Sclerotium rolfsii, evaluating mycelial growth and sporulation. Thus, samples of the plant material, finely powdered seeds, were extracted in 150 mM NaCl. The protein extracts were partially purified on Sephadex G-100 column, subjected to detection of inhibitors and SDS-PAGE (12.5%), and used in bioassays against the fungi. The electrophoretic profile revealed a single band in CfTI and eight bands in SPTI. The extracts of C. ferrea and S. polyphylla had an effect in reducing sporulation of the tested fungi, but S. rolfsii was inhibited only by C. ferrea. As to mycelial growth, the two extracts showed an effect on F. oxysporum and S. rolfsii, while C. guaranicola was inhibited only by S. polyphylla, and C. cassiicola by C. ferrea. It was concluded that seeds of C. ferrea and S. polyphylla present trypsin inhibitors. In addition, the results suggest that these tropical tree species are promising for the exploration of natural fungicides, since the extracts reduced mycelial growth and sporulation of C. guaranicola, C. cassiicola, F. oxysporum and S. rolfsii.