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Betulin derivatives containing a 1,2,3-triazole ring possess a wide spectrum of biological activities, including antiviral, anticancer, and antibacterial activity. A series of novel triazoles were prepared by the 1,3-dipolar cycloaddition reaction between the alkyne derivatives of betulin and organic azides. The chemical structures of the obtained compounds were defined by 1H and 13C NMR, IR, and high-resolution mass spectrometry (HR-MS) analysis. The target triazoles were screened for their antiviral activity against DNA and RNA viruses. The cytotoxic activity of the obtained compounds 5a–k and 6a–h was determined using five human cancer cell lines (T47D, MCF-7, SNB-19, Colo-829, and C-32) by a WST-1 assay. The bistriazole 6b displayed a promising IC50 value (0.05 μM) against the human ductal carcinoma T47D (500-fold higher potency than cisplatin). The microdilution method was applied for an evaluation of the antimicrobial activity of all of the compounds. The triazole 5e containing a 3′-deoxythymidine-5′-yl moiety exhibited antibacterial activity against two gram-negative bacteria vz. Klebsiella pneumoniae and Escherichia coli (minimal inhibitory concentration (MIC) range of 0.95–1.95 μM).

Electron paramagnetic resonance (EPR) spectroscopy was applied to measure the influence of two aminoglycoside antibiotics: gentamicin and kanamycin on free radical properties of DOPAmelanin. DOPA-melanin was formed by oxidative polymerization of 3,4-dihydroxyphenylalanine. Different concentrations of gentamicin and kanamycin (from 1 9 10 -4 to 1 9 10 -2 M) were used. o-Semiquinone free radicals with a g factor of 2.0043 were found in all studied melanin samples. Their concentrations in the DOPA-melanin-drug complexes were higher than in DOPA-melanin, and increased with the increase of gentamicin and kanamycin concentration. A single EPR line of the analyzed samples (ABp~, 0.48-0.52 mT) indicates that aminoglycoside antibiotics do not create a new type of free radicals in DOPA-melanin. Microwave saturation behavior of the experimental lines indicates the homogeneous broadening of resonance absorption curves for DOPA-melanin and its complexes with aminoglycosides. The EPR lines saturate at low microwave powers. Slow spin-lattice relaxation processes were characteristic for all studied melanin samples.

4) have been investigated. The structures of complexes 1, 2, and 3, have been determined by Xray crystallography. Compound 1 is a distorted trigonal-bipyramidal complex and compounds 2 and 3 adopt a distorted tetrahedral structure. Complex 1 is a single-strand polymer with a bridging 3,4-diaminobenzoato ligand coordinating via the O(1) atom of the carboxylato group and the nitrogen atom [a]