Antimicrobial activity, mechanism of action, and methods for stabilisation of defensins as new therapeutic agents

Bioactive compounds, such as antimicrobial peptides (AMPs), have increasingly been used recently to counteract the rapidly increasing incidence of bacterial resistance to usual antibiotics and chemotherapeutics. In humans, endogenous AMPs are part of the immune system and act against pathogens. Defensins compose a class of AMPs that have activity against gram-positive and -negative bacteria, viruses, and fungi. For some, antitumour activity has also been reported. Such characteristics indicate that they represent a potential new class of therapeutic agents against microorganisms, including multidrug resistant pathogens. However, pH and enzymatic degradation and variable tissue distribution of these compounds limit their clinical application. New technologies and different methods have been developed to overcome these limitations and increase their half-life, such as cyclization, lipidation, design of peptidomimetics, synthesis of hybrid peptides, and use of nanocarriers. The objective of this review was to analyse current applications of defensins as antimicrobial agents and their mechanism of action. Moreover, new technologies and methods for stabilizing defensins are discussed

ANALYTICAL STUDY AND ANTIMICROBIAL ACTIVITY OF ALPHA-DEFENSIN 2 DISSOLVED IN PHARMACOPOEIA BUFFERS WITH DIFFERENT pH

Human neutrophil peptides (HNPs, alpha-defensins) are a group of six defensins being considered as new antimicrobial drugs because of their multifunctional efficiency against bacteria, viruses and fungi. Regardless of the unique biological properties alpha-defensins are unstable compounds and their activity depends on many physical and chemical factors as well as on the kind of the used cultivation media. This leads to research difficulties and obstructions in their therapeutic application. The purpose of this study was to determine antibacterial activity of alpha-defensin 2 dissolved in pharmacopeia buffers and in parallel to develop selective and accurate analytical tests for identification and assay of alpha-defensin 2 in the course of study. The antibacterial effect of alpha-defensin 2 was determined against the strain Escherichia coli (ATCC 25922). It was found that 10 mg/l of Human neutrophil peptide-2 (HNP-2, alpha-defensin 2) dissolved in pH 9.0 buffer caused 90% inhibition of the bacterial respiratory activity. This buffer was considered as a suitable environment for deploying the antibacterial activity of the alpha-defensin. А selective MS analysis method for identification of alpha-defensin 2 in sample mixtures was developed. Also HPLC method with alternative selectivity was elaborated for identification and assay of mixtures containing alpha-defensin 2 and aminoacids in Mueller Hinton broth. The procedure includes development of system suitability test determination