Effects of light and temperature on isoprene emission at different leaf developmental stages of eschweilera coriacea in central Amazon / Efeitos da luz e da temperatura sobre a emissão de isopreno em diferentes estádios de desenvolvimento foliar de eschweilera coriacea na Amazônia Central

Isoprene emission from plants accounts for about one third of annual global volatile organic compound emissions. The largest source of isoprene for the global atmosphere is the Amazon Basin. This study aimed to identify and quantify the isoprene emission and photosynthesis at different levels of light intensity and leaf temperature, in three phenological phases (young mature leaf, old mature leaf and senescent leaf) of Eschweilera coriacea (Matamatل verdadeira), the species with the widest distribution in the central Amazon. In situ photosynthesis and isoprene emission measurements showed that young mature leaf had the highest rates at all light intensities and leaf temperatures. Additionally, it was observed that isoprene emission capacity (Es) changed considerably over different leaf ages. This suggests that aging leads to a reduction of both leaf photosynthetic activity and isoprene production and emission. The algorithm of Guenther et al. (1999) provided good fits to the data when incident light was varied, however differences among E S of all leaf ages influenced on quantic yield predicted by model. When leaf temperature was varied, algorithm prediction was not satisfactory for temperature higher than ~40 °C; this could be because our data did not show isoprene temperature optimum up to 45 °C. Our results are consistent with the hypothesis of the isoprene functional role in protecting plants from high temperatures and highlight the need to include leaf phenology effects in isoprene emission models.

O isopreno emitido pelas plantas corresponde em cerca de um terço das emissões globais de compostos orgânicos voláteis anualmente. A maior fonte de emissão de isopreno para a atmosfera global é a Bacia Amazônica. Este estudo objetivou identificar e quantificar a emissão de isopreno e fotossíntese em diferentes níveis de intensidade de luz e temperatura foliar, em três fases fenológicas (folha madura recente, folha madura tardia e folha senescente) de Eschweilera coriacea (Matamatá verdadeira) - a espécie com maior distribuição na Amazônia central. In situ, as medidas de fotossíntese e emissão de isopreno da folha madura recente apresentaram as maiores taxas em todos os níveis de luz e de temperatura. Adicionalmente, a capacidade de emissão de isopreno (ES) mudou consideravelmente entre as diferentes idades foliares, sugerindo que o envelhecimento reduz a atividade fotossintética e a produção/emissão de isopreno. O algoritmo de Guenther et al. (1999) demonstrou bom ajuste para a emissão de isopreno em diferentes intensidades de luz, entretanto, diferenças na ES entre as idades foliares influenciaram no rendimento quântico estimado pelo modelo. Em relação à temperatura foliar, a estimativa do algoritmo não foi satisfatória para as temperaturas acima de ~40 °C; isto provavelmente ocorreu pelo fato dos dados não apresentarem temperatura ótima até 45 °C. Nossos resultados são consistentes com a hipótese do isopreno ter um papel funcional para proteger as plantas de altas temperaturas e apontam a necessidade de incluir os efeitos da fenologia foliar em modelos de emissão de isopreno.

Photoionization and dissociation of the monoterpene limonene: mass spectrometric and computational investigation.

The photoionization of the monoterpene limonene has been studied using tunable vacuum ultraviolet synchrotron radiation in the region from the threshold for ionization of the parent molecule up to 15.5 eV. The adiabatic ionization energy of limonene is derived from photoionization efficiency spectrum and found to be 8.27 eV, compared with the density functional theory calculations which yields a value of 8.08 eV (B3LYP/6-311++G). Primary dissociation pathways of the parent molecule ions are investigated by experimental observations and theoretical calculations. Most of the fragmentation channels occur via a rearrangement reaction prior to dissociation. Transition structures and intermediates for those isomerization processes are also determined.

High irradiance curing and anomalies of exposure reciprocity law in resin-based materials.

OBJECTIVES: The aim of this work was to investigate the effect of high irradiance curing on resultant degree of conversion of 'flowable' resin composites and their counterpart higher viscosity paste materials. METHODS: Five commercial flowable materials (Venus; Heraeus Kulzer, Synergy D6; Coltene, Premise; Kerr, Grandio; Voco and Gradia; GC Corp) and their counterpart higher viscosity restorative versions were tested. Specimens were cured with a halogen Swiss Master Light (EMS, Switzerland) using five different curing protocols with similar radiant exposure (18J/cm(2)): 400mW/cm(2) for 45s, 900mW/cm(2) for 20s, 1500mW/cm(2) for 12s, 2000mW/cm(2) for 9s and 3000mW/cm(2) for 6s. Degree of conversion (DC) was measured in real time by Fourier transform near infrared spectroscopy (FT-NIRS). RESULTS: Three- and subsequent two way ANOVA testing revealed significant differences (p≤0.02) with respect to "composite type" and "cure protocol" for DC for all 5 product comparisons. Supplementary one-way ANOVA also revealed significant differences between curing protocols (p<0.05). The majority of higher viscosity resin composite paste materials exhibited similar DC regardless of curing protocol. However, a significant decrease in DC for specimens cured at 3000mW/cm(2) for 6s compared with 400mW/cm(2) for 45s was observed for the flowable materials, Grandio (41±0.36 and 62±1.15%, respectively) and Venus (44±0.44 and 67±0.44%, respectively). Conversely, other flowable materials exhibited little or no significant differences between curing modes. Generally, a higher degree of conversion was observed for flowables compared with their more viscous counterpart, except at high irradiance for those materials where a reciprocal relationship with exposure time was not observed. CONCLUSIONS: The validity of exposure reciprocity law and final degree of conversion depends on several factors, amongst which resin viscosity and filler content were important. Practitioners should be aware of the importance of resin composite constituents and irradiation protocols. Information on material composition and appropriate radiation sources by manufacturers may assist practitioners with the selection of appropriate curing protocols for specific material/light curing unit combinations with the aim of reducing the incidence of under-cured restorations and the clinical impact thereof.

Photoinitiator type and applicability of exposure reciprocity law in filled and unfilled photoactive resins.

OBJECTIVES: To test the influence of photoinitiator type and filler particle inclusion on the validity of exposure reciprocity law. MATERIALS AND METHODS: 50/50 wt% Bis-GMA/TEGDMA resins were prepared with equimolar concentrations of camphorquinone/DMAEMA (0.20/0.80 mass%) (CQ) or Lucirin-TPO (0.42 mass%), and were used either unfilled or filled to 75 mass%. Specimens were cured with a halogen Swiss Master Light (EMS, Switzerland) using four different curing protocols: 400 mW/cm² for 45 s as reference protocol (18 J/cm²), 1500 mW/cm² for 12 s (18 J/cm²), 3000 mW/cm² for 6 s (18 J/cm²) and 3 s (9 J/cm²). Degree of conversion (DC) was measured in real time for 70 s by FT-NIRS and temperature rise using a thermocouple. Depth of cure was determined with a penetrometer technique. RESULTS: With respect to DC and depth of cure, exposure reciprocity law did not hold for any tested material, except for the depth of cure of filled CQ-based materials. At similar radiant exposure, DC was significantly higher (p<0.05) for all unfilled and filled TPO-based materials compared with CQ-based materials. As exposure time was reduced and irradiance increased, TPO-based materials exhibited higher DC whilst an opposite trend was observed for CQ-based materials (p<0.05). For similar curing regimes, depth of cure of CQ-based materials remained significantly greater than that of TPO-based materials. Adding fillers generally reduced DC, except at higher irradiance for CQ-based materials where a positive effect was observed (p<0.05). SIGNIFICANCE: The validity of exposure reciprocity law was dependent on several factors, among which photoinitiator type and filler content were important. Lucirin-TPO is a highly reactive and efficient photoinitiator, which may allow the potential for a reduction in curing time of TPO-based photoactive materials in thin sections.

Irradiance differences in the violet (405 nm) and blue (460 nm) spectral ranges among dental light-curing units.

PROBLEM: Previous studies identified nonuniformity in the irradiance at the tip end of a variety of dental light-curing units (LCUs) and correlated those differences with potential clinical implications, but the spectral dependence of the irradiance uniformity has not yet been addressed. PURPOSE: This study examined the irradiance uniformity across emitting tips of LCUs at two emission wavelengths, 405 and 460 nm. Two broadband emission light units (quartz-tungsten-halogen [QTH] and plasma arc [PAC]), and four commercial light-emitting diode (LED)-type LCUs were examined. MATERIALS AND METHODS: The spectral radiant power from six LCUs was measured using a laboratory grade spectroradiometer (Ocean Optics, Dunedin, FL, USA). The spatial and spectral characteristics of irradiance across the emitting tips of these light units were recorded through 10-nm wide bandpass filters (centered at 405 nm [violet] or 460 nm [blue]) using a laser beam analyzer (Ophir-Spiricon, Logan, UT, USA). Irradiance distributions were reported using two-dimensional contour and three-dimensional isometric color-coded images. Irradiance uniformity at the tip end was determined using the Top Hat Factor (THF) for each filtered wavelength. RESULTS: Irradiance distributions from the QTH and PAC units were uniformly distributed across the tip end of the light guide, and THF values, measured through the 405 and 460-nm filters, were not significantly different. However, the three polywave LED units delivered non-uniform irradiance distributions with THF values differing significantly between the 405 and 460-nm emission wavelengths for each unit. Areas of nonuniformity were attributed to the locations of the various types of LED chips within the LCUs. CONCLUSION: All three polywave LED units delivered a nonuniform irradiance distribution across their emitting tip ends at the two important emission wavelengths of 405 nm and 460 nm, whereas the broadband light sources (QTH and PAC) showed no evidence of spectral inhomogeneity at these wavelengths.

Synthesis of a novel camphorquinone derivative having acylphosphine oxide group, characterization by UV-VIS spectroscopy and evaluation of photopolymerization performance.

Camphorquinone (CQ) derivatives having acylphosphine oxide (APO) group are unknown. This study synthesized such a novel 7,7dimethyl-2,3-dioxobicyclo[2.2.1]heptane-1-carbonyldiphenyl phosphine oxide (DOHC-DPPO = CQ-APO). Ultraviolet and visible (UVVIS) spectra of CQ-APO, CQ, and APO were measured. Photopolymerization performances of experimental light-cured resins comprising these photoinitiators were investigated. Newly synthesized CQ-APO showed as a pale yellow crystal (mp 365K). UV-VIS spectrum of CQ-APO showed two maximum absorption wavelengths (lambda(max)) [372 nm (from APO group) and 475 nm (from CQ moiety)] within 350-500 nm. Unfilled resin containing CQ-APO exhibited good photopolymerization time (9.6 sec) and relaxed operation time (50 sec), as well as a pronouncedly lower b value (4.0) in the CIELab color specification system than that containing CQ (84.0). Resin composites containing CQ-APO, exhibited high flexural strength (114.3-133.8 MPa). It was concluded that CQ-APO possessed two lambda(max )peaks within 350-500 nm, and that CQ-APO-containing resins exhibited excellent color tone, good photopolymerization reactivity, relaxed operation time, and high mechanical strength.

Dynamic monitoring of curing photoactive resins: a methods comparison.

OBJECTIVE: The aim of this investigation was to determine reaction enthalpy, ion viscosity and curing light transmission changes of unfilled methacrylate-based systems in order to compare methods that monitor photoactive resin polymerization. METHODS: Photoinitiator (0.2%, w/v, camphoroquinone), accelerator (0.3%, w/v, amine) and inhibitor (ranging from 0 to 1%, w/v, butylated hydroxytoluene, BHT) were incorporated in an experimental BisGMA/TEGDMA co-monomer mixture (50/50, w/v). The concentration of BHT was varied from 0.00, 0.01, 0.05, 0.10, 0.50 to 1.00% (w/v). Light transmission (LT), reaction enthalpy (UV-differential scanning calorimetry, DSC), and ion viscosity (dielectrical analysis, DEA) were determined during irradiation of the resins (40s; halogen light curing-unit). Statistical analysis was performed using two-way ANOVA followed by post hoc tests (alpha=0.05). Curve fitting and regression calculation were done. RESULTS: There was no significant change in the time to reach the maximum rate of polymerization (reaction time) in the individual systems up to a BHT concentration of 0.05% (P>0.05). Starting at a concentration of 0.10% BHT an increase in time of reaction could be found from 4.0s (LT), 4.07s (DEA) and 4.9s (DSC) to a maximum of 7.4s (DSC), 9.43s (DEA) and 9.67s (LT). Linear increase (y=5.588 x x) in time to the maximum speed of reaction could be found with a correlation of R(2)=0.992. CONCLUSIONS: The speed of polymerization reaction is strongly influenced by BHT concentration. The linear relationship should allow for the prediction of the speed of reaction during blending of a methacrylate-based resin. The three test systems allow for monitoring the complex polymerization kinetics of unfilled methacrylate-based systems.

Effect of resin-composite filler particle size and shape on shrinkage-strain.

OBJECTIVES: The aim of this study was to investigate the effect of variations in filler particle size and shape on the polymerization shrinkage-strain kinetics of resin-composites. METHODS: A model series of 12 VLC resin-composites were studied. The particulate dispersed phase volume fraction was 56.7%: these filler particles were systematically graded in size, and further were either spherical or irregular. The bonded disk method was used to determine shrinkage-strain kinetics. Displacement was recorded following 40s irradiation (600mW/cm(2)) at 23 degrees C (n=3). All data were captured for 60min and the final shrinkage-strain calculated. RESULTS: For materials with spherical filler, shrinkage-strain was 2.66% (SD 0.18) for those with irregular filler it was 2.89% (SD 0.11). These differences were statistically significant (p<0.001): the Scheffé test identified two subsets, those with irregular filler (including materials with a multimodal mix) and those with spherical filler (including materials with a multimodal mix). Additionally, there was a trend for higher shrinkage-strain values with decreasing filler particle size which was apparent for both those composites with spherical filler particles and those with irregular filler particles. For irregular filler particles, linear regression gave a high correlation (r(2)=0.99). SIGNIFICANCE: Statistically significant differences were identified in the shrinkage behavior of resin-composites with differing filler size and shape.

Influence of curing protocol on selected properties of light-curing polymers: degree of conversion, volume contraction, elastic modulus, and glass transition temperature.

OBJECTIVES: The purpose of this study was to investigate the effect of light-curing protocol on degree of conversion (DC), volume contraction (C), elastic modulus (E), and glass transition temperature (T(g)) as measured on a model polymer. It was a further aim to correlate the measured values with each other. METHODS: Different light-curing protocols were used in order to investigate the influence of energy density (ED), power density (PD), and mode of cure on the properties. The modes of cure were continuous, pulse-delay, and stepped irradiation. DC was measured by Raman micro-spectroscopy. C was determined by pycnometry and a density column. E was measured by a dynamic mechanical analyzer (DMA), and T(g) was measured by differential scanning calorimetry (DSC). Data were submitted to two- and three-way ANOVA, and linear regression analyses. RESULTS: ED, PD, and mode of cure influenced DC, C, E, and T(g) of the polymer. A significant positive correlation was found between ED and DC (r=0.58), ED and E (r=0.51), and ED and T(g) (r=0.44). Taken together, ED and PD were significantly related to DC and E. The regression coefficient was positive for ED and negative for PD. Significant positive correlations were detected between DC and C (r=0.54), DC and E (r=0.61), and DC and T(g) (r=0.53). Comparisons between continuous and pulse-delay modes of cure showed significant influence of mode of cure: pulse-delay curing resulted in decreased DC, decreased C, and decreased T(g). Influence of mode of cure, when comparing continuous and step modes of cure, was more ambiguous. SIGNIFICANCE: A complex relationship exists between curing protocol, microstructure of the resin and the investigated properties. The overall performance of a composite is thus indirectly affected by the curing protocol adopted, and the desired reduction of C may be in fact a consequence of the decrease in DC.

Photobleaching of camphorquinone during polymerization of dimethacrylate-based resins.

OBJECTIVE: The aim of this study was to compare the photobleaching rate of CQ in different dental resins. METHODS: The photodecomposition rate of CQ/amine system in bis-GMA/TEGDMA, bis-EMA and UDMA polymerizing monomers was evaluated at different light intensities. The photobleaching of the CQ was studied by monitoring the decrease in light absorption as a function of continuous irradiation time. The absorption changes were assessed by recording the transmitted light that passed through samples of monomers containing CQ/amine. RESULTS: Complete photobleaching of CQ was observed in all the monomer tested and the rate constant for the photobleaching was proportional to the radiation intensity. Hydrogen abstraction from amines by the excited CQ state via electron transfer and direct hydrogen abstraction from monomer structures were involved in the CQ photoreduction. CQ was photobleached in the absence of coinitiator in a dimethacrylate monomer containing a carbamate functional group (UDMA). This behavior was attributed to the presence of labile hydrogen atoms in the UDMA monomer. The CQ photobleaching rate constant in UDMA containing CQ/amine was similar to that in UDMA in the absence of amine. Moreover, the efficiency of CQ to photoinitiate the polymerization of UDMA in the absence of amine demonstrated that the radicals derived from the UDMA monomer via hydrogen abstraction are highly reactive toward double bonds. SIGNIFICANCE: CQ photoinitiates the polymerization of the UDMA monomer in the absence of amine and the efficiency of this process is comparable to that of traditional bis-GMA and bis-EMA monomers activated with CQ/amine.

Influence of photoinitiator type on the rate of polymerization, degree of conversion, hardness and yellowing of dental resin composites.

OBJECTIVES: To evaluate the degree of conversion (DC), maximum rate of polymerization (Rpmax), Knoop hardness (KHN) and yellowing (b-value) of resin composites formulated with phenylpropanedione (PPD), camphorquinone (CQ), or CQ/PPD at different concentrations. The hypotheses tested were (i) PPD or CQ/PPD would produce less Rpmax and yellowing than CQ alone without affecting DC and KHN, and (ii) Rpmax, DC, and KHN would be directly related to the absorbed power density (PDabs). METHODS: CQ/amine, PPD/amine and CQ/PPD/amine were used at low, intermediate and high concentrations in experimental composites. Photoinitiator absorption and halogen-light emission were measured using a spectrophotometer, Rp with differential scanning calorimetry (DSC), DC with DSC and FTIR, KHN with Knoop indentation; and color with a chromameter. The results were analyzed with two-way analysis of variance (ANOVA)/Student-Newman-Keul's test (p<0.05). Correlation tests were carried out between PDabs and each of DC, Rpmax and KHN. RESULTS: The PDabs increased with photoinitiator concentration and PPD samples had the lowest values. In general, maximum DC was comparable at intermediate concentration, while Rpmax and KHN required higher concentrations. DC was similar for all photoinitiators, but Rpmax was lower with PPD and CQ/PPD. PPD produced the lowest KHN. Yellowing increased with photoinitiator concentration. PPD did not reduce yellowing at intermediate and/or high concentrations, compared to CQ-formulations. PDabs showed significant correlations with DC, Rpmax and KHN. CONCLUSION: PPD or CQ/PPD reduced Rpmax in experimental composites without affecting the DC. The use of PPD did not reduce yellowing, but reduced KHN. DC, Rpmax and KHN were dependent on PDabs.

Photopolymerization of N,N-dimethylaminobenzyl alcohol as amine co-initiator for light-cured dental resins.

OBJECTIVE: The present study was carried out in order to assess the suitability of N,N-dimethylaminobenzyl alcohol (DMOH) as co-initiator of camphorquinone (CQ) and 1-phenyl-1,2-propanedione (PPD) in light-cured dental resins. METHODS: DMOH was synthesized and used as co-initiator for the photopolymerization of a model resin based on {2,2-bis[4-(2-hydroxy-3-methacryloxyprop-1-oxy)phenyl]propane} (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA). Experimental formulations containing CQ or PPD in combination with DMOH at different concentrations were studied. The photopolymerization was carried out by means of a commercial light-emitting diode (LED) curing unit. The evolution of double bonds consumption versus irradiation time was followed by near-infrared spectroscopy (NIR). The photon absorption efficiency (PAE) of the photopolymerization process was calculated from the spectral distribution of the LED unit and the molar absorption coefficient distributions of PPD and CQ. RESULTS: DMOH is an efficient photoreducer of CQ and PPD resulting in higher polymerization rate and higher double bond conversion compared with dimethylaminoethylmethacrylate. The PAE for PPD was higher than that for CQ. However, the polymerization initiated by PPD progressed at a lower rate and exhibited lower values of final conversion compared with the resins containing CQ. This observation indicates that the lower polymerization rate of the PPD/amine system should be explained in terms of the mechanism of generating primary radicals by PPD, which is less efficient compared with CQ. SIGNIFICANCE: The DMOH/benzoyl peroxide redox system, has recently been proposed as a more biocompatible accelerator for the polymerization of bone cements based on poly(methyl methacrylate), because cytotoxity tests have demonstrated that DMOH possesses better biocompatibility properties compared with traditional tertiary amines. The results obtained in the present study reveal the suitability of the CQ/DMOH initiator system for the polymerization of light-cured dental composites.

UV-VIS spectra and photoinitiation behaviors of acylphosphine oxide and bisacylphosphine oxide derivatives in unfilled, light-cured dental resins.

The aims of this study were to investigate the photoinitiation behaviors of acylphosphine oxide (APO) and bisacylphosphine oxide (BAPO) derivatives in comparison to D,L-camphorquinone (CQ)/tertiary amine (EDAB) system. Fifty six kinds of experimental unfilled, light-cured resins were prepared using APO, BAPO, CQ, EDAB, resin monomers, and adhesive monomers. The measurements of ultraviolet-visible (UV-VIS) spectroscopy, photopolymerization with differential scanning calorimeter (photo-DSC) and degree of conversion (DC) determination were performed. Results showed that the UV-VIS spectra of all APO and BAPO derivatives possessed lambda max ranging between 365 and 416 nm. Their photoinitiation behaviors were not influenced by acidic adhesive monomers formulated in unfilled Bis-GMA-based resins (p < 0.05). Although BAPO exhibited higher reactivity than CQ/EDAB in unfilled 6-methacryloyloxyhexcyl phosphonoacetate (6-MHPA)/ 2-hydroxyethyl methacrylate (HEMA) and 6-MHPA/glycerol monomethacrylate (GM)-based resins, it was found that there were no statistically significant differences in DC (%) between BAPO [44.2(6.5)-51.2(4.3)] and CQ/EDAB [42.4(4.4)-47.5(3.7)] (p < 0.05). It was concluded that APO and BAPO photoinitiators exhibited reactivity comparable to that of CQ/tertiary amine system.

Effects of visible light-irradiated camphorquinone and 9-fluorenone on murine oral mucosa.

The purpose of this study was to evaluate the histopathological effects of camphorquinone (CQ) and 9-fluorenone (9F) with or without visible light (VL) irradiation on the oral mucous membranes of mice. VL irradiation resulted in a higher degree of tissue damage after CQ or 9F application, particularly the latter. Necrosis and apoptosis were responsible for the tissue damage after application of either agent in the presence of VL irradiation.

Effect of UV irradiation on cut cantaloupe: terpenoids and esters.

Recent studies demonstrated that ultraviolet (UV) radiation enhanced terpenoids and decreased esters in thin-sliced cantaloupe. In preliminary studies treating fresh juices with UV, terpenoid compounds that normally were not isolated, or found in minute quantities, were elevated and only low molecular weight alcohols, ketones, and aldehydes decreased. Subsequently terpenoid induction/oxidation in UV-treated cut cantaloupe was reinvestigated. UV exposure increased the concentrations of terpenoids in cantaloupe tissue. However, UV exposure alone was not the sole factor responsible for enhanced terpenoids. UV-enhanced terpenoid production appears to be both cultivar- and maturity-dependent. Concomitant decreases in the ester content of UV-treated samples occurred using a previously published system. Yet, we established that almost identical ester losses occurred in thinly sliced laminar tissue receiving 60 min UV or air exposure in an open system. Tissue samples that were exposed to UV in a closed system often did not suffer correspondingly equal ester loss. Marked tissue warming (4.3 +/- 0.5 degrees C in 60 min) occurred during UV treatments in thin-sliced tissue. Ester loss from cantaloupe tissue was caused by the experimental procedure, but not by UV treatment per se. These findings are supported by the observation that UV is not responsible for chemical transformations to ester bonds, esterase, and lipase decrease in stored cut cantaloupe, and no lipid oxidation volatiles were observed in thin-sliced control tissue, while oxidized terpenoids were recovered. Information gathered indicates that improper cutting, handling, sanitation treatment, and storage can radically alter the desirable volatile aroma profile in cut cantaloupe, and potentially lead to decreased consumer acceptance.

Simultaneous determination of total hypericin and hyperforin in St. John's wort extracts by HPLC with electrochemical detection.

An analytical procedure was developed for the simultaneous determination of total hypericin (protopseudohypericin, pseudohypericin, protohypericin and hypericin) and hyperforin in Hypericum perforatum (St. John's wort) extracts and its preparations. The determination of total hypericin and hyperforin in one step was achieved by exposing the samples to artificial daylight in amber glass vials. This procedure allows both the photoconversion of the protoforms into the appropriate hypericins and the protection of the photosensitive hyperforin. For quantification, an HPLC method with electrochemical detection was applied. As an example of the application of the principle, two preparations containing St. John's wort were assayed.

Effects of combinations of ROS scavengers on oxidative DNA damage caused by visible-light-activated camphorquinone/N,N-dimethyl-p-toluidine.

The objective of this investigation was to analyze whether various combinations of the ROS scavengers glutathione (GSH), N-acetyl-cysteine (NAC), and vitamins C and E decrease DNA damage due to visible-light-irradiated (VL-irradiated) camphorquinone/N,N-dimethyl-p-toluidine (CQ/DMT) compared with individual vitamin C or E. PhiX-174 RF plasmid DNA was used to determine single and double strand breaks as parameters of DNA damage. Individual ROS scavengers and combinations of the antioxidants were added to plasmid DNA treated with VL-irradiated CQ/DMT/Cu (II). After incubation, DNA was loaded into a 1% agarose gel. Following electrophoresis, gels stained with 0.5 microg/mL ethidium bromide were photographed under ultraviolet illumination and analyzed with NIH ImageJ software. Results were evaluated between groups for statistical significance using Student's paired t-test (p < 0.05). Glutathione significantly reduced oxidative DNA damage at all test concentrations when combined with vitamin C or vitamin E. The concentration of damaged DNA observed in the presence of combinations of GSH with vitamin C or vitamin E was significantly lower compared with all other combinations of antioxidants investigated in our study (p < 0.05). In contrast to GSH, NAC was not able to compensate the pro-oxidative effects of vitamin C and vitamin E. Only at a concentration of 2 mM, NAC combined with vitamin C efficiently prevented CQ/DMT/Cu (II)-associated DNA damage. Our data indicate that solely the combinations of GSH with vitamin C or vitamin E significantly reduce the severity of oxidative DNA damage caused by CQ/DMT, whereas NAC may even increase the pro-oxidant activity of vitamin C and vitamin E.

A novel porphyrin-based photocatalytic system for terpenoids production from (R)-(+)-limonene.

A porphyrin-based photoexcited system has been revealed to be an efficient catalyst for d-limonene biotransformation under mild conditions and using molecular oxygen or/and H2O2 as oxidants. The influence of the oxidant, the wavelength of visible light, and the photoexcitation time on the catalytic system were studied for limonene oxidation with 5,10,15,20-tetraphenylporphyrin (H2TPP) as a catalyst. This porphyrin-catalyzed oxidation of limonene to three main products identified as carvone, an unknown product with a verbenone-like mass spectrum (1), and a (1S,4R)-p-mentha-2,8-diene 1-hydroperoxide (2). The highest conversion yield of these products was achieved at a very high molar ratio of H2TPP to limonene. The dependence of the biotransformation yield on the kind of solvent with different acceptor/donor electron properties was also investigated. Ethyl alcohol proved to be the best among the considered additives used for the reaction. Limonene photooxidation was not significantly dependent on wavelengths of visible light. It was concluded by UV-vis experiments that the reaction proceeds via a free-radical or/and molecular mechanism. Additional evidence for its radical nature was obtained from reactivity investigations. Maximal yield of carvone was obtained in the medium containing 90% of the substrate, within the period of 18 to 36 h of exposition to sunlight.

A natural component as coinitiator for unfilled dental resin composites.

A natural component, 1,3-benzodioxole (BDO), was used for the purpose of replacing the conventional amine for dental composite. Camphorquinone (CQ)/BDO was used to initiate the photopolymerization of urethane dimethacrylate (UDMA)/triethylene glycol dimethacrylate (TEGDMA) (70/30 wt %). The kinetics was recorded by real-time Fourier transformation infrared spectroscopy (FTIR). The mechanical properties were measured by dynamic mechanical analyzer (DMA), and CQ/ethyl 4-N,N-dimethylaminobenzoate (EDMAB) mixture was used as control in the same photocuring condition. The results indicated that, the addition of BDO as coinitiator greatly improved the rate of polymerization and final double bond conversion (DC), when compared with the system initiated by CQ alone. BDO and EDMAB were found to reach almost the same final DC (75%), though the kinetics of two systems was different. Comparing with EDMAB, BDO brought approximately the same glass transition temperature (Tg), but slightly higher storage modulus around 37 degrees C. The water sorption and solubility for two mixtures were almost the same and within the range of the ISO 4049's standards. These results suggested that BDO was an effective alternative to conventional amine for coinitiator. And the human diet characteristics of BDO made it more promising than amine in the dental resin formulations.