Treatment of infections caused by pathogenic bacteria is still harder. Due to increasing number of microbial species resistant against so far invented antibiotics. This presents great problem for public health. One of the potential solutions seems to be antimicrobial peptides. Those peptides are synthetized in all organisms as a part of innate immunity with rapid mode of antimicrobial action. Lot of them have been isolated from bacteria, plants, insects and mammals as well. Our project was aimed on finding such peptides in plant extracts, respectively in leaves of Brassica napus (canola), Solanum lycopersicum (tomato) and Tetragonia tetragonioides (New Zealand spinach). We used several separation techniques to obtain fractions containing compounds of peptide nature with hydrophobic character. Antimicrobial activity of these fractions was tested against several gram-positive and gram-negative bacteria. Mass spectrometry analysis of antimicrobial active fractions proved presence of low molecular peptides with molecular masses 1.9 - 4.9 kDa and a partial amino acid sequence in hydrophobic part of Tetragonia extract. In hydrophilic fraction of the Solanum extract with proved antibacterial activity two patogenesis-related proteins with antifungal activity NP24 and TPM-1 were detected.