N-Methylpiperazinyl amides of betulinic, platanic, glycyrrhetic, oleanolic, ursolic, and moronic acids were synthesized and modified. Betulin and betulonic acid showed antimicrobial activity against Staphylococcus aureus at a concentration of 90 mg/ml, and betulin manifested a bacteriostatic effect against Klebsiella pneumoniae at a concentration of 60 mg/ml. Among the studied N-methylpiperazinyl amides, the highest activity against S. aureus was observed for a betulonic acid derivative.

Natural peptides with antimicrobial activity are extremely diverse, and peptide synthesis technologies make it possible to significantly improve their properties for specific tasks. Here, we investigate the biological properties of the natural peptide indolicidin and the indolicidin-derived novel synthetic peptide In-58. In-58 was generated by replacing all tryptophan residues on phenylalanine in D-configuration; the α-amino group in the main chain also was modified by unsaturated fatty acid. Compared with indolicidin, In-58 is more bactericidal, more resistant to proteinase K, and less toxic to mammalian cells. Using molecular physics approaches, we characterized the action of In-58 on bacterial cells at the cellular level. Also, we have found that studied peptides damage bacterial membranes. Using the Escherichia coli luminescent biosensor strain MG1655 (pcolD'::lux), we investigated the action of indolicidin and In-58 at the subcellular level. At subinhibitory concentrations, indolicidin and In-58 induced an SOS response. Our data suggest that indolicidin damages the DNA, but bacterial membrane perturbation is its principal mode of action. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

The obtained results expand the perception of the role of haemoglobin in a living system, describing it as a source of multifunction substances. Additionally, the data presented in this paper may contribute to the development of new, cost-effective, antimicrobial agents.

The aim of the present review was to summarize the potential interactive effects between the gut microbiota and advanced glycation end-product (AGE) accumulation and toxicity in the host, and to reveal potential the mediatory effects of the gut microbiota on AGE-related health effects. The existing data demonstrate that dietary AGEs can have a significant impact on the richness and diversity of the gut microbiota, although the particular effect is dependent on the type of species, as well as the exposure dose. In addition, the gut microbiota may metabolize dietary AGEs. It has been also demonstrated that the characteristics of the gut microbiota, including its richness and relative abundance of certain taxa, is tightly associated with AGE accumulation in the host organism. In turn, a bilateral interplay between AGE toxicity and the modulation of the gut microbiota may contribute to pathogenesis of ageing and diabetes-associated diseases. Bacterial endotoxin lipopolysaccharide appears as the molecule that mediates the interactions between the gut microbiota and AGE toxicity, specifically via the modulation of the receptor for AGE signaling. Therefore, it is proposed that the modulation of the gut microbiota using probiotics or other dietary interventions may have a significant impact on AGE-induced glycative stress and systemic inflammation. Contents1. Introduction 2. Bacterial AGE metabolism 3. The impact of dietary AGE exposure on gut microbiota characteristics and host metabolism 4. Involvement of AGE-gut microbiota interplay in disease pathogenesis 5. Effects of gut microbiota modulation on AGE metabolism and toxicity 6. Role of lipopolysaccharide in the interplay between microbiota and AGE toxicity 7. Conclusions and future perspectives

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