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Chemical composition of the essential oils (EO) of Pelargonium graveolens, Leptospermum petersonii and Cymbopogon martinii var. motia, and the absolute of Rosa centifolia and their bioactivity were examined. Major compounds in P. graveolens EO were monoterpene alcohols citronellol, geraniol and linalool; in L. petersonii EO monoterpene aldehydes geranial, neral and citronellal; in C. martiniii var. motia EO monoterpene alcohol geraniol and ester geranyl acetate, while in absolute of R. centifolia aromatic alcohol 2-phenylethanol. The EO of L. petersonii showed the strongest antibacterial while the EO of C. martinii var. motia the strongest antifungal potential. The best biofilm inhibition capacity was observed with R. centifolia absolute. The results of scanning electron microscopy analysis indicated that the EOs of L. petersonii and P. graveolens changed the number and morphology of C. albicans cells. The L. petersonii EO was the most potent toward tumour cells and exhibited the best biological activity. This is first comparative report summarizing efficacy of studied aromatic samples against pathogenic microbes, providing deeper insight into the modes of antimicrobial action, and at the same time describing their cytotoxicity against cell lines.

This study focuses on the behavior of β-carotene and lutein inside multilamellar liposomes under continuous UV-irradiation. The liposomes were obtained by the thin film method and carotenoids (Crts) were incorporated by mixing at various concentrations (0.005, 0.0075, 0.02, 0.07 and 0.5 mol %). Liposomes formation and the presence of Crts inside them were confirmed by SEM microscopy and FT-IR spectroscopy, respectively. The antioxidant/pro- -oxidant activity of Crts inside liposomes was determined by the thiobarbituric acid–malondialdehyde (TBA–MDA) test. The investigated Crts acted more or less unexpected (as pro-oxidants) inside the lipid bilayers, interacting with the UV-produced lipid radicals and simultaneously suffering under the UV-irradiation. Their pro-oxidant activity with liposomes and under UV-irradiation could be explained by the formation of unstable adducts in the reaction with peroxyl radicals, or by Crts-cation radicals formation via the electron transfer mechanism. Such tentatively unexpected behavior of carotenoids should be taken into consideration in further carotenoids-based UV-filters projections in cosmetic formulations for skin protection. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR-34012]

The aim of this work was to give more accurate insight in the interaction of major photosynthesis pigment, chlorophyll (Chl), with copper (II) and zinc (II) in solution by flow injection analysis with electrospray ionization mass spectrometry (FIA-ESI-MS) method, as well as combined with ultra high performance liquid chromatography with DAD detection (UHPLC-DAD). These interactions may potentially, but not necessarily lead to formation of Cu-Chl and Zn-Chl complexes of two different types, which has a lot of - at least - disfunctional implications in plant world. The results based on analysis of full-scan and MS/MS spectra - with or without the UHPLC chromatograms - confirm formation of “central type” Cu-Chl complex, and “central type” Zn-Chl complex as well, along with a proof for formation of “peripheral” Zn-Chl complex, the latter one originating from a very week coordinative interaction at the edge of Chl structure. The used techniques appeared to be an efficient and reliable tool for studying formation and stability of heavy metals complexes with chlorophyll, at least in vitro, with a considerable possibility for assessment of real bio-environmental behavior. [Projekat Ministarstva nauke Republike Srbije, br. TR-34012 i br. OI-172044]

The study of the interaction of chromium with O-donor humic-like ligands is performed by electrospray-ionization mass spectrometry (ESI-MS) and ultraviolet/visible (UV/VIS) spectrophotometry. Heterogeneity of functional groups justifies the use of model compounds of humic substances. For studying the interaction of chromium with humic substances as model substances were used benzoic, salicylic, phthalic and citric acid, which include O-donor atoms, also present in heterogenous and polydispersed ligands, such humic and fulvic acids are. The intensity of the interaction is correlated with the acid-base and electron-donor properties, geometric and steric characteristics, and the number and the positions of O-donor atoms in the investigated ligands. UV/Vis data describing chromium interaction with humic-like ligands is placed in correlation with the ESI-MS data of the complexes, both in quantitative and in qualitative terms. UV/VIS spectroscopy and ESI-MS quantification showed a large difference in the informativeness of describing the interaction of chromium(III)-ligand, in favor of ESI-MS technique. ESI-MS technique can be used for quantitative analysis of the system Cr(III)-ligand. ESI-MS ion current chromatograms of 20 μL loop injections of systems Cr(III)-ligand, indicate a stabile peak and signal integrity.

Stability of Zn(II) and Cu(II) complexes of porphyrin derivatives (pheophytin and mesoporphyrin) to UV-B -irradiation has been studied by absorbance spectroscopy in 95% ethanol. The chosen porphyrins as well as their heavy metal complexes undergo photochemical decomposition obeying first-order kinetics. In general, pheophytin is more stable than mesoporphyrin to UV-B irradiation. On the other hand, stability of Zn(II)-complex is smaller than Cu(II)-complex both for pheophytin and mesoporphyrin; however while Cu(II)-complex with pheophytin is more stable than the one with mesoporphyrin, with Zn(II)-complex the situation is vice versa.

The aim of this work is to estimate the degradation and change in antioxidant activity of quercetin in the presence of two different mixtures of phospholipids in methanol solution, under continuous UV-irradiation from three different sub-ranges (UV-A, UV-B and UV-C), in the presence and in the absence of selected UV-absorbing photosensitizer, benzophenone. Quercetin is employed to control lipid peroxidation process generated by UV-irradiation, by absorbing part of the UV-incident light, or/and by scavenging the involved, created free radicals. The results show that quercetin undergoes to irreversible destruction, highly dependent on UV-photons energy input, more expressed in the presence than in the absence of benzophenone. In the same time quercetin expresses suppression effect on lipid peroxidation processes in UV-irradiated phospholipid mixtures in both cases - absence or presence of benzophenone (more or less effective, respectively). In UV-C-irradiated mixtures, benzophenone photosensitizing function is significantly reduced due to its strong absorption in the same UV-C spectral range, therefore affecting less antioxidant activity of the remained quercetin.

Irreversible degradation of quercetin and rutin, dissolved in methanol and water, induced by continuous UV-irradiation from two different sub-ranges (UV-B and UV-C) has been studied in this work. The degradation of both flavonoids is related to formation of UV-induced degradation products: both processes follow first-order kinetics. The degradation and products formation rate constants are both dependent on the involved UV-photons energy input in both solvents.

The stabilities of four selected carotenoids dissolved in hexane, two carotenes and two xanthophylls, toward UV-irradiation of three different ranges (UV-A, UV-B and UV-C) were studied in this work. The carotenoids underwent bleaching via a probable free radical mediated mechanism following first-order kinetics. The bleaching rates were highly dependent on the input of the involved photons and, although not consistently, on the chemical structures of the investigated compounds. For the two xanthophylls, a possible role of oxygen associated with their bleaching cannot be neglected.

The stability of chlorophylls toward UV irradiation was studied by Vis spectrophotometry in extracts containing mixtures of photosynthetic pigments in acetone and n-hexane. The chlorophylls underwent destruction (bleaching) obeying first-order kinetics. The bleaching was governed by three major factors: the energy input of the UV photons, the concentration of the chlorophylls and the polarity of the solvent, implying different molecular organizations of the chlorophylls in the two solvents.

The effects of ultraviolet radiation (UV) on the antioxidant action of three selected carotenoids (β-carotene, lycopene and lutein) in the presence of a lipoidal lecithin mixture were studied by the DPPH (1,1-diphenyl-2-picrylhydrazyl) test. The test is based on the measurement of the decrease of the free DPPH radical absorbance at 517 nm caused by the antioxidant action of carotenoids, which appeared to be strongly affected by UV-action. The high-energy input of the involved UV-photons plays a major governing role.

The aim of this work was to study the anticipated antioxidant role of four selected carotenoids in mixtures with lecithin lipoidal compounds in hexane solution, under continuous UV-irradiation in three different ranges (UV-A, UV-B and UV-C). Two carotenes (b-carotene and licopene) and two xantophylls (lutein and neoxanthin) were employed to control the lipid peroxidation process generated by UV-irradiation, by scavenging the involved free radicals. The results show that while carotenoids undergo a substantial, structural dependent destruction (bleaching), which is highly dependent on energy of the UV-photons, their contribution to the expected suppression of lecithin peroxidation is of marginal importance, not exceeding a maximum of 20%. The marginal antioxidant behaviour has been attributed to a highly unordered hexane solution, where the scavenging action of the carotenoids becomes less competitive.

The possibility of the formation of copper and zinc complexes with chlorophyll in photosynthetic organelles (chloroplasts) and suborganelles (thylakoids) was studied. The visible and fluorescence spectra obtained from chloroplasts and thylakoids in the presence of the two metals confirmed complex formation in the case of copper, while such possibility appears to be very minor in the case of zinc. The reason for this distinction lies in the different type of complexes which chlorophyll forms with the two metals: only "central" or "substitution" copper-chlorophyll complexes may be formed inside the two isolated entities, while the formation of a possible zinc-chlorophyll "peripheral" type of complex is prevented for steric reasons. The latter fact is of high biological relevance, since both complexes may cause an irreversible impairment and damage of photosynthetic function.

Complexes of copper and zinc with chlorophyll, the major photosynthesis pigment, were studied by Vis, FTIR and fluorescence spectroscopy. Two types of complexes were recognized. While copper replaces the central magnesium atom of chlorophyll to form a "central" Cu-Chl complex, this was not proposed in the case of zinc. Instead, the zinc-mediated formation of a 6-membered chelate cycle fused at the periphery of the chlorophyll structure is proposed. The latter event could be ascribed to allomerization reactions of chlorophyll.

Mixed insoluble monolayers (Langmuir films) of 1,2-di-O-linoleoyl-3-sn-phosphatidylcholine (1,2-DLPC) and incorporated benzophenone-type photosensitizers at an air-water interface were exposed to prolonged UV-irradiation. The irradiation was initiated at a particular fixed molecular packing value. Changes of the surface pressure during the UV-induced photolysis of the sensitizers were plotted against the irradiation time and the results were interpreted in terms of the molecular lipid/sensitizer ratios inside the monolayers.

Laser-flash photolysis has been employed to characterize the behaviour of the free radicals created in the photochemical reaction of benzophenone (BZP), as well as of its lipoidal derivative, benzophenone-4-heptyl-4’-pentanoic acid (BHPA), with chosen unsaturated fatty acids in sodium dodecyl sulphate micelles. The calculated rate constants were used to study the "cage effect" i.e., the recombination of the created radical-pairs (BZP, BHPA ketyl radical - lipid radical) inside the highly limited space of the SDS micelles. The "cage effect" appears to be the dominant event inside SDS micelles, dependent on the structure of both the reactants-precursors. The fractions of the initially created radical-pairs which escape the "cage effect" and exit into the surrounding aqueous phase do not exceed 16 %. This fact is of enormous importance for the self-control of the pathogenic process of lipid peroxidation.

Simultaneous measurements of fluorescence and thermal emission have been performed by applying combined fluorescence and photoacoustic techniques on isolated thylakoids pretreated by prolonged illumination with saturating light. The traces were used to create Lineweaver-Burk type plots, proving clearly at least a formal analogy between the kinetics of the mechanisms governing fluorescence and thermal emission from isolated thylakoids and Michaelis-Menten kinetics of enzymatic reactions. Two characteristic parameters were calculated from them (energy storage and half-saturation light intensity) in order to obtain a basic, initial response of the photosynthetic apparatus functioning under photoinhibition stress.

The goal of this work was to study the possibility of the occurrence of radical- type lipid peroxidation of the lipid constituents on biomembranes, in compressed monolayers, having lipoidal benzophenone photosensitizers incorporated. The triplets of the photosensitizer abstract allylic and doubly-allylic hydrogen atoms from anticonjugated moities of the lipid molecules. The results simultaneously confirmed the occurrence of H-abstraction (and so the initiation of the peroxidizing chain mechanism), and the absence of the formation of lipid peroxides. The reason lies in "cage effect": the highly restricted spacial area of compressed lipid monolayers limits the mobility of the created radicals (lipid radicals and ketyl radicals) and leads to their recombination, thus preventing the propagation step of the chain mechanism. With certain reservations it may be concluded that these results have a clear implication on real biomembranes: the structure of which is one of themain factors preventing the spread of the chain reaction, and the formation of lipid peroxides.

The stabilities and antioxidant action of two selected flavonoids, quercetin and rutin, dissolved in methanol and water, toward continuous UV-irradiation from three different sub-ranges (UV-A, UV-B and UV-C) were studied. The flavonoids underwent degradation (bleaching) following first-order kinetics. The bleaching rates were highly dependent on the energy input of the involved UV-photons. The antioxidant activities of the two flavonoids on UV-induced lecithin lipid peroxidation were studied by the thiobarbituric acid-malondialdehyde (TBA-MDA) test, and appeared to be also affected by the continuous UV irradiation. The energy input of the incident UV-photons again played a major governing role, but an impact of the flavonoids structures cannot be neglected. [ABSTRACT FROM AUTHOR]

A study of the interaction of chromium with O-donor humic-like ligands war performed using electrospray-ionization mass spectrometry (ESI-MS) and ultraviolet/visible (UV/Vis) spectrophotometry. The heterogeneity of the functional groups justifies the use of model compounds of humic substances. For studying the interaction of chromium with humic substances, benzoic, salicylic, phthalic and citric acid, which include O-donor atoms also present in heterogeneous and polydispersed ligands, such as humic and fulvic acids, were used as model substances. The intensity of the interaction is correlated with the acid--base and electron-donor properties, geometric and steric characteristics, and the number and the positions of the O-donor atoms in the investigated ligands. UV/Vis data describing chromium interaction with humic-like ligands was placed in correlation with ESI-MS data of the complexes, both in quantitative and in qualitative terms. UV/Vis spectroscopy and ESI-MS quantification showed a large difference in the information they yield in describing the interaction of chromium(III) with the ligand, the ESI-MS technique being more informative. ESI-MS Technique can be used for quantitative analysis of the system Cr(III)--ligand. ESI-MS ion current chromatograms of 20 µL loop injections of systems Cr(III)--ligand, indicate a stabile peak and signal integrity. [ABSTRACT FROM AUTHOR]