MTT based L-aminoacid oxidase activity test for determination of antivenom potency against Vipera ammodytes envenomation

Synthesis, Antimicrobial Activity, and Tyrosinase Inhibition by Multifunctional 3,4-Dihydroxy-Phenyl Peptidomimetics

The purpose of the present study was to evaluate the synergistic effect of two important pharmacophores, 3,4-dihydroxyphenyl and peptidomimetic moieties, as mushroom tyrosinase inhibitors and antimicrobial agents targeting specific strains of pathogenic bacteria. The 3,4-dihydroxybenzaldehyde (protocatechuic aldehyde) was found to be an effective inhibitor of tyrosinase activity, and due to the fact that it is a safe natural substance with such a scaffolded structure, it is likely that dihydroxyl-substituted phenolic derivatives can exhibit potent tyrosinase inhibitory activity. Series of peptidomimetics with an incorporated 3,4-dihydroxyphenyl scaffold was synthesized and characterized. The inhibitory effects of peptidomimetics on a mushroom tyrosinase were studied. The results showed that among the compounds, five of them showed higher inhibitory activity than the parent 3,4-dihydroxybenzyl aldehyde. In silico docking studies with mushroom tyrosinase (PDB ID 2Y9X) predicted possible binding modes in the enzymatic pocket for these compounds. Furthermore, the antimicrobial activities of peptidomimetics against selected Gram-positive and Gram-negative bacterial strains (E. coli, A. baumannii, P. aeruginosa, E. cloacae, and S. aureus) were investigated. The results showed that all tested peptidomimetics have antimicrobial activities (MIC values from 0.25 to 4.0 μM) comparable with those observed for the commonly used antibiotics (ciprofloxacin, bleomycin, and cloxacillin). Notably, all evaluated compounds demonstrated significant activity against E. coli and S. aureus strains, which are primary sources of infections resulting in numerous fatalities. Additionally, the cytotoxicity of sixteen derivatives was assessed using the MTT assay on BALB/c3T3 mouse fibroblast cell lines. Cytotoxicity analyses indicated that the tested substances have a similar or reduced impact on cell proliferation compared to commonly utilized antibiotics within the range of therapeutic doses. This study presents the potential of peptidomimetics with 3,4-dihydroxyphenyl scaffolds could be beneficial for developing novel tyrosinase inhibitors and new potent food preservatives or cosmetic additives.

The Venom of Vipera ammodytes ammodytes: Proteomics, Neurotoxic Effect and Neutralization by Antivenom

Deep proteomic analyses identified, in total, 159 master proteins (with 1% FDR and 2 unique peptides) from 26 protein families in the venom of Vipera ammodytes ammodytes (Vaa). Data are available via ProteomeXchange with the identifier PXD056495. The relative abundance of PLA2s is 11.60% of the crude venom, of which 4.35% are neurotoxic Ammodytoxins (Atxs). The neurotoxicity of the venom of Vaa and the neutralizing effect of the antivenom were tested on the neuromuscular preparation of the diaphragm (NPD) of rats. The activity of PLA2 in the venom of Vaa and its neutralization by the antivenom were determined under in vitro conditions. The Vaa venom leads to a progressive decrease in NPD contractions. We administered pre-incubated venom/antivenom mixtures at various ratios of 1:2, 1:10 and 1:20 (w/w) and observed the effects of these mixtures on NPD contractions. The results show that the mean effective time (ET50) for NPD contractions with the 1:20 mixture is highly significantly different (p < 0.001) from the ET50 for the venom and the ET50 for the 1:2 and 1:10 mixture ratios. We also found a highly significant (p < 0.001) reduction in Na+/K+-ATPase activity in the NPD under the influence of the venom. The reduction in the activity of this enzyme was reversible by the antivenom. Under in vitro conditions, we have achieved the complete neutralization of PLA2 by the antivenom. In conclusion, the antivenom abolished the venom-induced progressive decrease in NPD contractions in a concentration-dependent manner. Antivenom with approximately the same mass proportion almost completely restores Na+/K+-ATPase activity in the NPD and completely neutralizes the PLA2 activity of the venom in vitro.

Mystery of the Passerini Reaction for the Synthesis of the Antimicrobial Peptidomimetics against Nosocomial Pathogenic Bacteria

The first example of applying salicylaldehyde derivatives, as well as coumarin with the formyl group at the C8 position in its structure, as carbonyl partners in a three-component Passerini reaction, is presented. As a result of research on the conditions of the Passerini reaction, the important role of the hydroxyl group in the salicylaldehyde used in the course of the multicomponent reaction was revealed. When an aldehyde with an unprotected hydroxyl group is used, only two-component α-hydroxy amide products are obtained. In contrast, the use of acylated aldehyde results in three-component α-acyloxy amide products with high efficiency. The developed protocol gives access to structurally diversified peptidomimetics with good yield. The compounds were also evaluated as antimicrobial agents against selected strains of nosocomial pathogenic bacteria. The structure-activity relationship revealed that inhibitory activity is strongly related to the presence of the trifluoromethyl group (CF3) or the methyl group at the C4 position in an unsaturated lactone ring of the coumarin scaffold. MIC and MBC studies were carried out on eight selected pathogenic bacteria strains (Gram-positive pathogenic Staphylococcus aureus strain (ATCC 23235), as well as on Gram-negative E. coli (K12 (ATCC 25404), R2 (ATCC 39544), R3 (ATCC 11775), and R4 (ATCC 39543)), Acinetobacter baumannii (ATCC 17978), Pseudomonas aeruginosa (ATCC 15442), and Enterobacter cloacae (ATCC 49141) have shown that the tested compounds show a strong bactericidal effect at low concentrations. Among all agents investigated, five exhibit higher antimicrobial activity than those observed for commonly used antibiotics. It should be noted that all the compounds tested showed very high activity against S. aureus, which is the main source of nosocomial infections that cause numerous fatalities. Additionally, the cytotoxicity of sixteen derivatives was measured with the use of the MTT test on BALB/c3T3 mouse fibroblast cell lines. The cytotoxicity studies revealed that the tested substances exert a similar or lower effect on cell proliferation than that observed for commonly used antibiotics within the range of therapeutic doses. A parallel MTT assay using ciprofloxacin, bleomycin, and cloxacillin showed that these antibiotics are more cytotoxic when tested in mammalian cells, and cell viability is in the range of 85.0-89.9%. Furthermore, we have shown that the studied coumarin-based peptidomimetics, depending on their structural characteristics, are nonselective and act efficiently against various Gram-positive and Gram-negative pathogens, which is of great importance for hospitalised patients.