Coal-Derived Humic Substances: Insight into Chemical Structure Parameters and Biomedical Properties.

An investigation was carried out on humic substances (HSs) isolated from the coal of the Kansk-Achinsk basin (Krasnoyarsk Territory, Russia). The coal HSs demonstrate the main parameters of molecular structure inherent to this class of natural compounds. An assessment was performed for the chemical, microbiological, and pharmacological safety parameters, as well as the biological efficacy. The HS sample meets the safety requirements in microbiological purity, toxic metals content (lead, cadmium, mercury, arsenic), and radionuclides. The presence of 11 essential elements was determined. The absence of general, systemic toxicity, cytotoxicity, and allergenic properties was demonstrated. The coal HS sample was classified as a Class V hazard (low danger substances). High antioxidant and antiradical activities and immunotropic and cytoprotective properties were identified. The ability of the HS to inhibit hydroxyl radicals and superoxide anion radicals was revealed. Pronounced actoprotective and nootropic activities were also demonstrated in vivo. Intragastric administration of the HS sample resulted in the improvement of physical parameters in mice as assessed by the "swim exhaustion" test. Furthermore, intragastric administration in mice with cholinergic dysfunction led to a higher ability of animals with scopolamine-induced amnesia to form conditioned reflexes. These findings suggest that the studied HS sample is a safe and effective natural substance, making it suitable for use as a dietary bioactive supplement.

The Influence of Silver-Containing Bionanomaterials Based on Humic Ligands on Biofilm Formation in Opportunistic Pathogens.

The uncontrolled use of antibiotics has led to a global problem of antimicrobial resistance. One of the main mechanisms of bacterial resistance is the formation of biofilms. In order to prevent the growth of antimicrobial resistance, it is crucial to develop new antibacterial agents that are capable of inhibiting the formation of biofilms. This makes this area of research highly relevant today. Promising candidates for these antibacterial agents are new bionanomaterials made from natural humic substances and silver nanoparticles. These substances have the potential to not only directly kill microorganisms but also penetrate biofilms and inhibit their formation. The goal of this study is to synthesize active pharmaceutical substances in the form of bionanomaterials, using ultradispersed silver nanoparticles in a matrix of coal humic substances, perform their characterization (NMR spectroscopy, TEM, and ICP-AES methods), and research their influence on biofilm formation in the most dangerous opportunistic pathogens (E. coli, Methicillin-resistant St. Aureus, K. pneumoniae, P. aeruginosa, St. aureus, A. baumannii, and K. Pneumonia). The results showed that all of the studied bionanomaterials had antibacterial activity against all of the opportunistic pathogens. Furthermore, they were found to have a suppressive effect on both pre-existing biofilms of these bacteria and their formation.

Enhanced Antioxidant Activity and Reduced Cytotoxicity of Silver Nanoparticles Stabilized by Different Humic Materials.

The current article describes the biological activity of new biomaterials combining the "green" properties of humic substances (HSs) and silver nanoparticles. The aim is to investigate the antioxidant activity (AOA) of HS matrices (macroligands) and AgNPs stabilized with humic macroligands (HS-AgNPs). The unique chemical feature of HSs makes them very promising ligands (matrices) for AgNP stabilization. HSs have previously been shown to exert many pharmacological effects mediated by their AOA. AgNPs stabilized with HS showed a pronounced ability to bind to reactive oxygen species (ROS) in the test with ABTS. Also, higher AOA was observed for HS-AgNPs as compared to the HS matrices. In vitro cytotoxicity studies have shown that the stabilization of AgNPs with the HS matrices reduces the cytotoxicity of AgNPs. As a result of in vitro experiments with the use of 2,7-dichlorodihydrofluorescein diacetate (DCFDA), it was found that all HS materials tested and the HS-AgNPs did not exhibit prooxidant effects. Moreover, more pronounced AOA was shown for HS-AgNP samples as compared to the original HS matrices. Two putative mechanisms of the pronounced AOA of the tested compositions are proposed: firstly, the pronounced ability of HSs to inactivate ROS and, secondly, the large surface area and surface-to-volume ratio of HS-AgNPs, which facilitate electron transfer and mitigate kinetic barriers to the reduction reaction. As a result, the antioxidant properties of the tested HS-AgNPs might be of particular interest for biomedical applications aimed at inhibiting the growth of bacteria and viruses and the healing of purulent wounds.