Mechanochemically Induced Anion Exchange in Aminoazobenzene Salts

Aminoazobenzene sulfate salt reacts with the crystals of KBr in solid-state under high pressure yield-ing corresponding bromide salt. The reactant and product differ also in the position of protonation, amino group, and azo group, respectively. Since protonation of azo-group destroys the coplanarity of two benzene rings and diminishes -conjugation, the product differs from the reactant also in color, from orange to violet. Hence, the reaction is the example of the piezochromic effect. This solid-state process is studied by kinetic measurements, and the structures of the compounds were analyzed by X-ray chrystallography

Application of 4-amino-N-adamantylphthalimide solvatochromic dye for fluorescence microscopy in selective visualization of lipid droplets and mitochondria

4-Amino-N-adamantylphthalimide (1) is a dye with moderate absorptivity (in CH3CN ε363 = 4200 M-1 cm-1) and high quantum yield of fluorescence (ΦF = 0.15-0.80) that exhibits fluorosolvatochromic properties. The dye can be excited at 405 nm and the position of fluorescence maximum and the Stokes shift are well correlated with the ET(30) parameter. The excitation in the near-visible part of the spectrum and low cytotoxicity allow use of the dye in live cell microscopy. Due to its amphiphilic character, the dye stains artificial membranes in liposomes. Using confocal microscopy on two human cancer cell lines, we have shown that 1 stains primarily intracellular lipid droplets. Colocalization experiments with different organelle markers indicated that 1 additionally stains mitochondrial membranes. The fluorosolvatochromism of 1 allows the simultaneous visualization of mitochondria and intracellular lipid droplets in two separate emission channels, which has a potential use in cells and tissues exhibiting intense oxidative metabolism of lipids

NanoUPLC-QTOF-MS/MS Determination of Major Rosuvastatin Degradation Products Generated by Gamma Radiation in Aqueous Solution

Rosuvastatin, a member of the statin family of drugs, is used to regulate high cholesterol levels in the human body. Moreover, rosuvastatin and other statins demonstrate a protective role against free radical-induced oxidative stress. Our research aimed to investigate the end-products of free radical-induced degradation of rosuvastatin. To induce the radical degradation, an aqueous solution of rosuvastatin was irradiated using different doses of gamma radiation (50–1000 Gy) under oxidative conditions. Rosuvastatin and related degradation products were separated on nanoC18 column under gradient elution, and identification was carried out on hyphenated nanoUPLC and nanoESI-QTOF mass spectrometer system. Elemental composition analysis using highly accurate mass measurements together with isotope fitting algorithm identified nine major degradation products. This is the first study of gamma radiation-induced degradation of rosuvastatin, where chemical structures, MS/MS fragmentation pathways and formation mechanisms of the resulting degradation products are detailly described. The presented results contribute to the understanding of the degradation pathway of rosuvastatin and possibly other statins under gamma radiation conditions

Photophysical and photochemical properties of resveratrol and its reactions with biologically relevant free radicals

Poznato je da prirodni spoj trans-resveratrol (trans-3,5,4'-trihidroksistilben, ArOH) posjeduje izrazitu biološku aktivnost. Unatoč poznavanju mogućih mehanizama antioksidacijskog djelovanja kojima se pridjeljuje protektivna uloga ArOH u živim organizmima, o njegovim kemijskim svojstvima se malo zna. Cilj ove disertacije je istražiti kinetike i mehanizme reakcija ArOH s do sada neistraženim radikalima koji nastaju u uvjetima stanja oksidacijskog stresa. Ovi radikali i pobuđena stanja ArOH generirani su svjetlosnim pulsom koristeći rubinski i Nd:YAG laserski uređaj odnosno pulsom ubrzanih elektrona. Tranzijentnom apsorpcijskom spektroskopijom detektirane su intermedijerne vrste te određene konstante brzina reakcija ArOH s radikalima lokaliziranim na kisiku, ugljiku i sumporu odnosno s aril-ketonima u tripletnim stanjima. Reakcije su praćene na vremenskim skalama reda veličine 1061012 s u acetonitrilu i otopinama alkohol/voda. Budući da je poznato da su istraživani radikali odgovorni za poremećaje u odvijanju normalnih procesa u stanicama živih organizama, rezultati ovih istraživanja su originalan doprinos razumijevanju mehanizama i kinetike reakcija ArOH s biološki značajnim radikalima.It is well known that natural compound trans-resveratrol (trans-3,5,4'-trihydroxystilbene) possesses significant biological activity. However, despite the knowledge of its possible antioxidant mechanisms which have a protective role in the living organisms, chemical properties of ArOH are less known. The main goal of this thesis is to investigate reaction kinetics and mechanisms of ArOH with so far unresearched free bioradicals which occur in the conditions of oxidative stress. These free radicals and ArOH excited states were generated with ruby or Nd:YAG laser flash or electron accelerator pulse. Short-lived intermediate species of ArOH and its reaction kinetics with oxygen, sulphur and carbon-centered radicals and aromatic carbonyl triplets were determined with transient absorption spectroscopy. Measurements were conducted at the 1061012 sec time scales in acetonitrile and solutions of water/alcohol. This research is original contribution to the understanding of the mechanism and reaction kinetics of ArOH antioxidant activity with biologically relevant free radicals under investigation which are known to be responsible for the malfunction of the normal processes in living cells

Photophysical and photochemical properties of resveratrol and its reactions with biologically relevant free radicals

Poznato je da prirodni spoj trans-resveratrol (trans-3,5,4'-trihidroksistilben, ArOH) posjeduje izrazitu biološku aktivnost. Unatoč poznavanju mogućih mehanizama antioksidacijskog djelovanja kojima se pridjeljuje protektivna uloga ArOH u živim organizmima, o njegovim kemijskim svojstvima se malo zna. Cilj ove disertacije je istražiti kinetike i mehanizme reakcija ArOH s do sada neistraženim radikalima koji nastaju u uvjetima stanja oksidacijskog stresa. Ovi radikali i pobuđena stanja ArOH generirani su svjetlosnim pulsom koristeći rubinski i Nd:YAG laserski uređaj odnosno pulsom ubrzanih elektrona. Tranzijentnom apsorpcijskom spektroskopijom detektirane su intermedijerne vrste te određene konstante brzina reakcija ArOH s radikalima lokaliziranim na kisiku, ugljiku i sumporu odnosno s aril-ketonima u tripletnim stanjima. Reakcije su praćene na vremenskim skalama reda veličine 1061012 s u acetonitrilu i otopinama alkohol/voda. Budući da je poznato da su istraživani radikali odgovorni za poremećaje u odvijanju normalnih procesa u stanicama živih organizama, rezultati ovih istraživanja su originalan doprinos razumijevanju mehanizama i kinetike reakcija ArOH s biološki značajnim radikalima.It is well known that natural compound trans-resveratrol (trans-3,5,4'-trihydroxystilbene) possesses significant biological activity. However, despite the knowledge of its possible antioxidant mechanisms which have a protective role in the living organisms, chemical properties of ArOH are less known. The main goal of this thesis is to investigate reaction kinetics and mechanisms of ArOH with so far unresearched free bioradicals which occur in the conditions of oxidative stress. These free radicals and ArOH excited states were generated with ruby or Nd:YAG laser flash or electron accelerator pulse. Short-lived intermediate species of ArOH and its reaction kinetics with oxygen, sulphur and carbon-centered radicals and aromatic carbonyl triplets were determined with transient absorption spectroscopy. Measurements were conducted at the 1061012 sec time scales in acetonitrile and solutions of water/alcohol. This research is original contribution to the understanding of the mechanism and reaction kinetics of ArOH antioxidant activity with biologically relevant free radicals under investigation which are known to be responsible for the malfunction of the normal processes in living cells

Photophysical properties and electron transfer photochemical reactivity of substituted phthalimides

Photochemical reactivity, photophysical and electrochemical properties for a series of N-adamantylphthalimides bearing carboxylic functional groups were investigated. Upon irradiations (with or without a triplet sensitizer), compounds undergo decarboxylation via a photoinduced electron transfer (PET) from the carboxylate to the phthalimide. UV-Vis and fluorescence pH titrations were used to determine pKa values for the prototropic forms, which were put in connection with quantum yields of the reaction (ΦR). Compounds bearing electron donors OH and OCH3 at the phthalimide 4 position are fluorescent (ΦF = 0.02-0.49) and PET takes place from both singlet and triplet excited states. Estimated rate constants for PET in the singlet excited states for methoxy- and amino-substituted phthalimides are (2.0 ± 0.1) × 10^9 s-1and (3.4 ± 1.0) × 10^7 s-1, respectively. Laser flash photolysis (LFP) was conducted to characterize triplet excited states, which are populated less efficiently for compounds with electron donors. The PET is reversible and the overall ΦR depends on the rates for back electron transfer, protonation of the phthalimide radical anion and decarboxylation. Plausible photochemical and photophysical pathways depend on the phthalimide substituents, which is important for the use of phthalimide derivatives in organic synthesis and photocatalysis