FEATURES OF OBTAINING GELS BASED ON AGAR-AGAR FOR COSMETOLOGY AND MEDICINE WITH ANTIBACTERIAL PROPERTIES

In the modern world, special attention is paid to materials with controlled characteristics. In this aspect, polymers and materials based on them have a number of specific properties for effective use in medicine and cosmetology. Humic substances satisfy most of these features, so their use is very important. The study of the features of the processes of gelation in polymer systems such as agar-agar, which has rather universal properties, makes it possible to use it as a basis for gels and polymer carriers, as well as in the processes of obtaining medical and cosmetic materials with different properties, which can be important in solving a number of topical issues. In particular, these are lightweight and cheap to manufacture antiseptic gels, dressings on wounds with absorption and protective properties, all kinds of cosmetics. In the article, a study was carried out to study the processes of gelation and the features of the rheological properties of hydrogels based on agar-agar in order to obtain modern hydrogels with an antibacterial effect. It was found that the introduction of humic acids into the composition of polymer hydrogels slows down the processes of structure formation, which leads to a decrease in the viscosity of all the studied compositions. Also, a decrease in the melting temperature of hydrogel jellies with an increase in the content of humic acids in them indicates a reduced level of gelation, which also leads to an increase in the time of loss of stickiness of polymer hydrogels. It has been shown that humic acids in polymer hydrogels have high antibacterial activity and almost completely stop the processes of mold formation in them. It was found that the most effective from the point of view of obtaining hydrogels with an antibacterial effect are agar-agar compositions with a humic acid content of 15 %. Thus, cosmetic polymer hydrogels with an antibacterial effect have been developed, which can be used in the treatment of hands, face and other areas of the skin that are open and contact for humans to combat coronavirus bacteria.

Microwave-Assisted Rapid Synthesis of Eu(OH)3/RGO Nanocomposites and Enhancement of Their Antibacterial Activity against Escherichia coli

Nanomaterials with high antibacterial activity and low cytotoxicity have attracted extensive attention from scientists. In this study, europium (III) hydroxide (Eu(OH)3)/reduced graphene oxide (RGO) nanocomposites were synthesized using a rapid, one-step method, and their antibacterial activity against Escherichia coli (E. coli) was investigated using the synergistic effect of the antibacterial activity between Eu and graphene oxide (GO). The Eu(OH)3/RGO nanocomposites were prepared using a microwave-assisted synthesis method and characterized using X-ray diffraction, scanning electron microscopy, photoluminescence spectroscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. Raman sprectroscopy and X-ray diffraction confirmed the pure hexagonal phase structure of the nanocomposites. Further, the antibacterial properties of Eu(OH)3/RGO were investigated using the minimum inhibitory concentration assay, colony counting method, inhibition zone diameter, and optical density measurements. The results revealed that the Eu(OH)3/RGO exhibited a superior inhibition effect against E. coli and a larger inhibition zone diameter compared to RGO and Eu(OH)3. Further, the reusability test revealed that Eu(OH)3/RGO nanocomposite retained above 98% of its bacterial inhibition effect after seven consecutive applications. The high antibacterial activity of the Eu(OH)3/RGO nanocomposite could be attributed to the release of Eu3+ ions from the nanocomposite and the sharp edge of RGO. These results indicated the potential bactericidal applications of the Eu(OH)3/RGO nanocomposite.

Antibacterial Activities of Prenylated Isoflavones from Maclura tricuspidata against Fish Pathogenic Streptococcus: Their Structure-Activity Relationships and Extraction Optimization

Streptococcus zoonotic bacteria cause serious problems in aquaculture with clinical effects on humans. A structure-antibacterial activity relationships analysis of 22 isoflavones isolated from M. tricuspidata (leaves, ripe fruits, and unripe fruits) against S. iniae revealed that prenylation of the isoflavone skeleton was an important key for their antibacterial activities (minimum inhibitory concentrations: 1.95–500 μg/mL). Through principal component analysis, characteristic prenylated isoflavones such as 6,8-diprenlygenistein (4) were identified as pivotal compounds that largely determine each part’s antibacterial activities. M. tiricuspidata ripe fruits (MTF), which showed the highest antibacterial activity among the parts tested, were optimized for high antibacterial activity and low cytotoxicity on fathead minnow cells using Box–Behnken design. Optimized extraction conditions were deduced to be 50%/80 °C/7.5 h for ethanol concentration/extraction temperature/time, and OE-MTF showed contents of 6,8-diprenlygenistein (4), 2.09% with a MIC of 40 µg/mL. These results suggest that OE-MTF and its active isoflavones have promising potential as eco-friendly antibacterial agents against streptococcosis in aquaculture.

In vitro antimicrobial activity screening of new Heterocyclic compounds derived from 5-bromo-2,3-di(furan-2-yl)-1h-indole

This article describes the antimicrobial activity evaluation of new heterocyclic compounds derived from 5-bromo-2,3-di(furan-2-yl)-1h-indole. Heterocyclic moiety serve as perfect framework on which pharmacophores can be effectively attached to produce novel drugs. New compounds were obtained on the basis of derivatives including 1H-indole-2,3-dione derivatives. Acid-catalyzed, three-component reaction (Belinelli synthesis) between 5-bromo-2,3-di(furan-2-yl)1H-indole, acetylacetone and semi carbazide, thiosemicarbazone, urea, thiourea, guanidine constitutes a rapid and facile synthesis of corresponding tetrahydro pyrimidines, which are interesting compounds with a potential for pharmaceutical application. Antimicrobial tests revealed high antibacterial activity of obtained derivatives. The synthesized compounds have been screened for their in vitro antimicrobial activity against various strains of bacteria and fungi. Keywords: Vitro; Heterocyclic Compounds; Antimicrobial

An Antibacterial Peptide with High Resistance to Trypsin Obtained by Substituting d-Amino Acids for Trypsin Cleavage Sites

The poor stability of antibacterial peptide to protease limits its clinical application. Among these limitations, trypsin mainly exists in digestive tract, which is an insurmountable obstacle to orally delivered peptides. OM19R is a random curly polyproline cationic antimicrobial peptide, which has high antibacterial activity against some gram-negative bacteria, but its stability against pancreatin is poor. According to the structure-activity relationship of OM19R, all cationic amino acid residues (l-arginine and l-lysine) at the trypsin cleavage sites were replaced with corresponding d-amino acid residues to obtain the designed peptide OM19D, which not only maintained its antibacterial activity but also enhanced the stability of trypsin. Proceeding high concentrations of trypsin and long-time (such as 10 mg/mL, 8 h) treatment, it still had high antibacterial activity (MIC = 16–32 µg/mL). In addition, OM19D also showed high stability to serum, plasma and other environmental factors. It is similar to its parent peptide in secondary structure and mechanism of action. Therefore, this strategy is beneficial to improve the protease stability of antibacterial peptides.