Biljana Šmit

Novel seleno-hydantoin palladium(II) complex - antimigratory, cytotoxic and prooxidative potential on human colon HCT-116 and breast MDA-MB-231 cancer cells.

Selenium and palladium containing compounds separately exert multifunctional effects on cells. While selenium containing compounds usually exert antioxidative properties, palladium(II) containing compounds are cytotoxic and prooxidative. Here we investigated biological effects of bicyclic seleno-hydantoin cis-7a-ethyl-5-methyl-5-phenylselanylmethyl-tetrahydro-pyrrolo[1,2-c]imidazole-1,3-dione (Hid-Se), and its palladium(II) complex, trans-bis-(cis-7a-ethyl-5-methyl-5-phenylselanylmethyl-tetrahydro-pyrrolo[1,2-c]imidazole-1,3-dionato) palladium(II) chloride ((Hid-Se)2Pd) on human colon HCT-116 and breast MDA-MB-231 cancer cell lines. Hid-Se and (Hid-Se)2Pd showed prooxidative and cytotoxic character. In all performed experiments (Hid-Se)2Pd proved to be more active, i.e. this substance exerted greater prooxidative effect, cytotoxicity and influence on cell migration potential. Even though Hid-Se and (Hid-Se)2Pd enhanced migration of HCT-116 cells, very important feature of these substances is the strong antimigratory potential on metastatic MDA-MB-231 cells.

Experimental and theoretical elucidation of structural and antioxidant properties of vanillylmandelic acid and its carboxylate anion

Vanillylmandelic acid (VMA), an important metabolite of catecholamines that is routinely screened as tumor marker, was investigated by the various spectroscopic techniques (IR, Raman, UV-Vis, antioxidant decolorization assay and NMR). Structures optimized by the employment of five common functionals (M05-2X, M06-2X, B3LYP, CAM-B3LYP, B3LYP-D3) were compared with the crystallographic data. The M05-2X functional reproduced the most reliable experimental bond lengths and angles (correlation coefficient >0.999). The importance of intramolecular hydrogen bonds for structural stability was discussed and quantified by the NBO analysis. The most prominent bands in vibrational spectrum were analyzed and compared to the experimental data. The positions of the carbon and hydrogen atoms in NMR spectra were well reproduced. The differences in UV-Vis spectrum were investigated by adding the explicit solvent and by performing NBO and QTAIM analyses. The discrepancy in the two spectra of about 50nm could be explained by the solvent effect on carboxyl group. The most probable antioxidant activity mechanism was discussed for VMA and its carboxylate anion. The Molecular Docking study with the C - reactive protein additionally proved that variety of functional groups present in VMA and its anion allowed strong hydrogen and hydrophobic interactions.

Synthesis and theoretical investigation of some new 4-substituted flavylium salts

Synthetic flavylium salts possess the same basic structure as anthocyanins and their color and physical-chemical properties are notably dependent on the nature and position of the functional groups attached to the skeleton. Influence of position C-4 is very dominant in the stabilization of these molecules and the presence of substituent at that position is highly desirable for a food colorant because it would be stable over a wide range of pH values. Flavylium salts substituted at 4-position with bulky hydroxyphenyl substituents were synthesized by acidic condensation according to a slightly modified procedure described by Robinson and Walker. Their thermodynamic properties and conformational analysis have been studied at DFT level.

Mechanism, kinetics and selectivity of selenocyclization of 5-alkenylhydantoins: an experimental and computational study

Summary The mechanism and selectivity of a bicyclic hydantoin formation by selenium-induced cyclization are investigated. The proposed mechanism involves the intermediates formed by an electrophilic addition of the selenium reagent on a double bond of the starting 5-alkenylhydantoin prior the cyclization. These intermediates are readily converted into the more stable cyclic seleniranium cations. A key step of the mechanism is an intramolecular cyclization which is realized through an anti-attack of the internal nucleophile, the amidic nitrogen, to the seleniranium cation yielding the intermediate imidazolinium cations. Their deprotonation is followed by the formation of the fused bicyclic reaction products. Important intermediates and key transition states are studied by using density functional theory (DFT) methods. The pathways of the reaction are investigated in detail. There are two regioselective pathways related to 5-exo and 6-endo products. Theoretical calculations and the monitoring of the cyclization reaction using 1H NMR spectroscopy are in a good agreement with the proposed mechanism and are consistent with our experimental results. The preferred pathway for formation of 5-exo products is confirmed.