ABSTRACT
The objective of this work was to purify and evaluate the antifungal potential of peptides present in immature and ripe fruits of Capsicum chinense Jacq. (accession UENF 1706) on the medical importance yeasts. Initially the proteins of these seedless fruits were extracted, precipitated with ammonium sulfate at 70% saturation, followed by heating at 80 °C. Subsequently, the peptide-rich extract was fractionated by DEAE-Sepharose anion exchange. The whole process was monitored by tricine-SDS-PAGE. The results revealed that the fraction retained in anion exchange column, called D2, of immature and ripe fruits significantly inhibit the growth of Candida albicans and C. tropicalis yeasts. Due to the higher yield, the D2 fraction of immature fruits was selected for further purification by reverse phase chromatography on HPLC, where sixteen different fractions (H1-H16) were obtained and these were subjected to antifungal assay at 50 µg mL-1. Although almost all fractions tested had significant growth inhibition, the HI9 fraction inhibit 99% of the two yeasts tested. The effect of treatment with HI3, HI8, HI9, and HI14 fractions on the viability of yeast cells was analyzed due to their strong growth inhibition. We observed that only 50 µg mL-1 of the HI9 fraction is the lethal dose for 100% of the cells of C. albicans and C. tropicalis in the original assay. Although the HI9 fraction had a fungicidal effect on both tested yeasts, we only observed membrane permeabilization for C. tropicalis cells treated with 50 µg mL-1 of this fraction. Through mass spectrometry, we identified that the 6 kDa peptide band of HI9 fraction showed similarity with antimicrobial peptides belonging to the plant defensin family.
