Chitin-binding peptides from Capsicum annuum with antifungal activity and low toxicity to mammalian cells and Galleria mellonella larvae

In recent years, there have been several reports of the presence of toxic proteins in cultivated or wild plant species, which are implicated in plant defense mechanisms. The existence of these proteins raises the possibility of biotechnological applications originating from the development of new techniques to combat diseases caused by fungi. In this context, there are chitin-binding proteins. Chitin is an essential component of the fungal cell wall, so chitin-binding proteins are important in controlling fungal growth. Thus, the objective of this study was to characterize and evaluate the in vitro antimicrobial effect of peptides with chitin binding properties isolated from Capsicum annuum seeds on the growth of the genus Candida. Initially, proteins were extracted in phosphate pH 5.4, and a chitin column was equilibrated with sodium acetate (0.08 M, pH 4.5), where 50 mg of the peptide-rich heated fraction from each species was applied. Subsequently, the retained material was eluted with 0.1 M HCl. Tricine SDS-PAGE was used to visualize the peptides. After chromatography, two fractions, F1 (not retained in the chitin column) and F2 (retained in the chitin column, named Ca-F2), were obtained. Electrophoresis showed major protein bands between 3 and 14 kDa. Electrophoresis from chitin affinity chromatography also showed major bands between 3 and 14 kDa, especially for Ca-F2 retained in the column. One peptide obtained from the F2 fraction was identified by mass spectrometry and showed similarity to seed 2S albumin, named Ca-Alb2S. Ca-F2 inhibited the growth of C. albicans and C. tropicalis, was not toxic to mammalian cells and still had a high survival rate when tested in vivo on Galleria mellonella larvae. This is the first report of chitin-binding peptides isolated from Capsicum seeds through an affinity column and their biological activities. These studies are at an early stage; therefore, other tests are needed to study the mechanism of action of the fraction, since the findings indicate great potential for the development of new antifungal molecules.