Fluorescence Evaluation of Scavenging Efficiency of Antioxidants Against Reactive Oxygen Species (ROS) in Cigarette Smoke

Cigarette smoke can cause cellular oxidative stress that contributes to various adverse health effects associated with smoke exposure, partially due to reactive oxygen species (ROS) present in cigarette smoke. Reduction of abundant ROS in the cigarette mainstream smoke (MSS) is of importance for human health. In this work, a simple, rapid, and reliable fluorescence evaluation of scavenging efficiency of antioxidants as potential filter additives against ROS in cigarette smoke is reported. This method was based on the combination of model glass reactor and a fluorescence assay of ROS in cigarette smoke using dihydrorhodamine 6 G (DHR-6 G). The antioxidant was added into a glass reactor attached to cigarette filter, which simplified the preparation of combined filter containing additives. The ROS scavenging efficiency of antioxidants was then determined using spectrofluorimetry by the change in fluorescence intensity of whole smoke-bubbled solutions before and after addition of antioxidants into the glass reactor. The proposed method was successfully applied to the determination of ROS scavenging efficiency of several potential additives, such as tert-butylhydroquinone (TBHQ), vitamin C, β-carotene, grape seed extract, and Ginkgo biloba extract. Moreover, the relationship between MSS ROS scavenging efficiency and antioxidant activities (DPPH radicals scavenging efficiency and Fe²⁺ reducing power) of these compounds was also investigated.     

Chemiluminescence of Cigarette Smoke: Salient Features of the Phenomenon

The study disclosed herein provides for the first time a detailed experimental support for the general mechanism of the cigarette‐smoke‐derived chemiluminescence, as an example par excellence of the excited‐state generation in a chemically complex aerosol medium. The mechanism involves chemiexcitation in a unimolecular transformation of the smoke‐borne free radical species. However, the concentration of these radicals, , obeys a bimolecular (second‐order) kinetics and depends on a particulate‐phase content (total particulate matter, TPM) of the cigarette smoke. The decrease in with increasing the TPM amount manifests radical‐scavenging propensity of the smoke particulate phase. Astonishingly, no energy transfer takes place from the primary excited light‐emitting species to luminophoric molecules abundant in the smoke. The reported results build up fundamentals of a facile chemiluminescence assay for free radical properties of the smoke. The experimental approaches developed for this study are of general scope and may be used for mechanistic elucidation of the excited‐state generation in chemical systems and environments of an arbitrary complexity.     

Antioxidant,antimicrobial, and tyrosinase inhibition activities of acetone extract of <Emphasis Type="Italic">Ascophyllum nodosum</Emphasis>

The search for new antioxidants of natural origin derived from plants and seaweeds is still very important at present. In our study, the acetone extract of A. nodosum was investigated for its potential use as a natural antioxidant, natural feed additive with antibacterial activity and as a tyrosinase inhibitor. This study could be useful in the context of improved utilization of the A. nodosum extract in the food and cosmetics industry, being not only economically advantageous but also environmentally friendly. Extracts showed antioxidant activity with application of different methodologies: 1,1-diphenyl-2-picrilhydracil DPPH· radicals scavenging (39 %, 4 mg of freeze-dried sample), β-carotene-linoleic acid antioxidant assay (11 %, 4 mg of freeze-dried sample), O₂· radicals scavenging activity (IC₅₀ 0.43 mg mL⁻¹), OH· radicals scavenging activity (IC₅₀ 1.55 mg mL⁻¹), and iron chelation ability (IC₅₀ 0.56 mg mL⁻¹). The extract showed considerable antibacterial activity being more effective against gram-positive bacteria (Micrococcus luteus, Staphylococcus aureus) than against gram-negative bacteria (Escherichia coli, Enterococcus aerogenes). Results of tyrosinase assay for the acetone extract of Ascophyllum nodosum presented 65.6 % inhibition of tyrosinase activity at the IC₅₀ value of 0.1 mg mL⁻¹. The outcomes of our study support potential utilization of this brown seaweed as a source of natural antioxidants. Antioxidant activity of the studied seaweed can be apparently explained by the free radicals scavenging activity, particularly related to the mechanisms of O₂⁻· radicals scavenging activity, OH· radicals inactivation, and iron chelation ability.     

Analysis of Vinyl Chloride in Vapor Phase of Mainstream Cigarette Smoke by GC–MS Under ISO and Health Canada Intensive Machine Smoking Regimens

Vinyl chloride (VC) in the vapor phase of mainstream cigarette smoke was determined under both International Organization for Standardization (ISO) and Health Canada intensive (HCI) machine smoking regimens, which was suspected to be carcinogenic compound. VC was collected by passing the mainstream cigarette smoke through a Cambridge Filter Pad (CFP) into cryogenic traps containing methanol. The impinger solutions were fortified with VC-d ₃ and analyzed by GC–MS. Limits of detection for vinyl chloride was 0.9 ng mL⁻¹ with the recovery in the range of 93.2–98.4 %. Moreover, the intra-day and inter-day precision was 7.39 and 9.77 %, respectively. Under HCI machine smoking regimen, the vinyl chloride yields in vapor phase of mainstream cigarette smoke were much higher and the average increase was greater than 100 % compared with those under ISO smoking condition.

     

Self-assembled mono- and bilayers on gold electrodes to assess antioxidants—a comparative study

Oxidative stress is considered as an imbalance of reactive species over antioxidants, leading to diseases and cell death. Various methods have been developed to determine the antioxidant potential of natural or synthetic compounds based on the ability to scavenge free radicals. However, most of them lack biological relevance. Here, a gold-based self-assembled monolayer (SAM) was compared with a gold-supported lipid bilayer as models for the mammalian cell membrane to evaluate the free radical scavenging activity of different antioxidants. The oxidative damage induced by reactive species was verified by cyclic and differential pulse voltammetry and measured by the increase of electrochemical peak current of a redox probe. Trolox, caffeic acid (CA), epigallocatechin gallate (EGCG), ascorbic acid (AA), and ferulic acid (FA) were used as model antioxidants. The change in the decrease of the electrochemical signal reflecting oxidative membrane damage confirms the expected protective role. Both model systems showed similar efficacies of each antioxidant, the achieved order of radical scavenging potential is as follows: Trolox > CA > EGCG > AA > FA. The results showed that the electrochemical assay with SAM-modified electrodes is a stable and powerful tool to estimate qualitatively the antioxidative activity of a compound with respect to cell membrane protection against biologically relevant reactive species.

     

Removal of Model Pollutants in Aqueous Solution by Gliding Arc Discharge: Determination of Removal Mechanisms. Part I: Experimental Study

The respective roles of short and long-life oxidant species in the degradation of model organic pollutants in water have been investigated in a gas–liquid gliding arc plasma reactor. Three different model pollutants were treated in two configurations: direct discharge mode and spatial post discharge mode. In each case the pollutants were classified according to their ease of removal, from easier to more difficult to remove. The results were as follows: phenol >> 1-heptanol >> pCBA. The removal mechanisms also are different depending on the characteristics of the pollutant treated. Phenol (100 % of phenol was removed for energy density = 1.20 × 10⁵ J/L) was supposed to react strongly with NO₂° radicals produced by the dissociation of N₂O₄ in liquid phase. The degradation of 1-heptanol would proceed by desorption of the liquid phase to the gas phase, where oxidation occurs due to the plasma active short-lived species. In the case of pCBA, oxidation occurs in the liquid solution, but the degradation is low because of its low reactivity with species such as ozone and °NO₂ and insufficient production of OH° radicals in the solution.     

香烟烟雾中自由基的检测

对香烟焦油中的Q/H2Q自由基及气相中的自由基进行了测定，同时对香烟燃烧产生自由基的机理进行了探讨。     

Functionalized graphene quantum dots loaded with free radicals combined with liquid chromatography and tandem mass spectrometry to screen radical scavenging natural antioxidants from Licorice and Scutellariae

A novel screening method was developed for the detection and identification of radical scavenging natural antioxidants based on a free radical reaction combined with liquid chromatography with tandem mass spectrometry. Functionalized graphene quantum dots were prepared for loading free radicals in the complex screening system. The detection was performed with and without a preliminary exposure of the samples to specific free radicals on the functionalized graphene quantum dots, which can facilitate charge transfer between free radicals and antioxidants. The difference in chromatographic peak areas was used to identify potential antioxidants. This is a novel approach to simultaneously evaluate the antioxidant power of a component versus a free radical, and to identify it in a vegetal matrix. The structures of the antioxidants in the samples were identified using tandem mass spectrometry and comparison with standards. Fourteen compounds were found to possess potential antioxidant activity, and their free radical scavenging capacities were investigated. The order of scavenging capacity of 14 compounds was compared according to their free radical scavenging rate. 4′,5,6,7‐Tetrahydroxyflavone (radical scavenging rate: 0.05253 mL mg^?1 s^?1) showed the strongest capability for scavenging free radicals.     

On‐line HPLC method for screening of antioxidants against superoxide anion radical from complex mixtures

A practical approach for rapidly screening antioxidants against superoxide anion radicals from complex mixtures was developed based on the quantitative difference in active compounds before and after their reaction. To test the effectiveness of the approach, seven flavonoids with antioxidative properties were investigated both individually and in a mixture. Using the approach, antioxidants could be rapidly separated and screened with a ranked order of activities in the meantime. The radical scavenging activities were in the following order: quercetin > kaempferol > fisetin > puerarin > luteolin > rutin > baicalein. The order of activity was conducted by comparing the scavenging ratio of the antioxidant, which was completely consistent with the results obtained from the traditional electronic spin resonance. Then, the method was successfully applied to black tea extracts. This approach is fast and convenient for screening, isolating, and analyzing potential antioxidants from a mixture with good quantitative and reproducible ability.     

Presence of peroxyradicals in cigarette smoke and the scavenging effect of shikonin, a naphthoquinone pigment

Using a new method having been developed for the purpose of quantitative determination for peroxyradicals, the presence of peroxyradicals was proved in cigarette smoke. In brief, peroxyradicals in cigarette smoke were measured by ESR spectrometry coupled to non-reductive scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH). As a result, peroxyradicals were found to be major reactive oxygen species (ROS) since the concentration of peroxyradicals recovered from cigarette smoke was much higher than that of any of other ROS (superoxide and hydroxyl radical) and nitric oxide. Furthermore, several antioxidants (ascorbic acid, reduced glutathione, epigallocatechin gallate, shikonin) were examined for scavenging activity against peroxyradicals in the cigarette smoke. Among them shikonin alone exerted the scavenging activity, suggesting that shikonin is promising antioxidant for cigarette filters because of its effectiveness against broad range of ROS including peroxyradicals, heat resistance, nonvolatility and high affinity to the filter.     

Why is the order reversed? peroxyl‐scavenging activity and fats‐and‐oils protecting activity of vitamin E

The orders of relative tocopherol biopotency, scavenging activity of lipid peroxyl radicals, and quenching activity of singlet oxygen are as follows: jalpha‐tocopherol > β‐tocopherol ? γ‐tocopherol > δ‐tocopherol. However, the reverse is the case for the activity to protect fats and oils from oxidation: jalpha‐tocopherol < β‐tocopherol < γ‐tocopherol δ‐tocopherol. The reason for this reverse has been studied by measuring weight gains of solutions including methyl linoleate and various antioxidants at daily intervals. Antioxidant activity is expressed as an induction period in days. Induction periods are compared with the second‐order rate constants for scavenging of an aroxyl radical by the antioxidants. A plot of the logarithm of the second‐order rate constant vs. the induction period is found to give a good linear fit, and the slope is negative. From these results, it is considered that the larger the peroxyl‐radical‐scavenging activity of a tocopherol, the more favorable the production of the tocopheroxyl radical, and thus the more efficient the oxidation of fats and oils by the tocopheroxyl radical. This is not the case for tocopherols in vivo, because vitamin C and ubiquinol reduce tocopheroxyl radicals formed from tocopherols. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 605–610, 2005     

Novel silylphenol antioxidants by density functional theory

We have scrutinized five novel silylphenol antioxidants, including 2-silylphenol ( 1 ), 4-silylphenol ( 2 ), 2,6-disilylphenol ( 3 ), 2,4-disilylphenol ( 4 ), and 2,4,6-trisilylphenol ( 5 ), at M06/6–311++G** level of theory. To evaluate the antioxidant efficiency, the electronic effects on O─H bond dissociation energy (BDE) and vertical ionization potential (IP_v) of 1 – 5 are investigated, which are mainly governed by electronic effects. The conductor-like polarized continuum model (CPCM) is applied to measure the antioxidant capacity in the solution phase. The results show that antioxidants with the lowest BDE and IP_v values can efficiently act via hydrogen atom transfer (HAT) and single electron transfer (SET) mechanisms, respectively. The stability of resulting radicals is measured by nucleus independent chemical shift (NICS) index, natural bond orbital (NBO) analysis, and nucleophilicity (N) index. The BDE shows lower values in the gas phase with respect to water, while water exhibits lower IP_v values than gas. Structure 5 turns out as the most efficient antioxidant. The overall order of antioxidant efficiency in both gas and water phases is 5 > 2 > 3 > 4 > 1 .     

一种测定主流卷烟烟气中固相自由基总量的新方法

研究了一种准确测定主流卷烟烟气中固相自由基总量的新方法. 通常人们采用剑桥滤片来捕集主流卷烟烟气中的固相自由基, 但它并不适合用于准确测定主流卷烟烟气中的固相自由基的总量, 研究发现有超过20%的主流卷烟烟气中的固相自由基可以透过剑桥滤片. 找到了一种电子顺磁共振波谱(EPR)信号很小的、适合用来捕集主流卷烟烟气中的固相自由基总量的过滤片. 采用了以在相同条件下测得的1,1-二苯基-2-苦基肼基(1,1-Diphenyl-2-picryl-hydrazyl, 简称DPPH)的EPR信号强度与强煤的EPR信号强度相比得到的相对EPR信号强度与自由基的自旋数建立校准曲线的方法来计算烟气固相自由基的量, 降低了使用不同的电子自旋共振波谱仪造成的对同一种检测样品测定结果的差异. 通过不同实验室内和实验室间的验证实验, 证明了此方法有很好的重复性和重现性.     

Identification and in vitro antioxidant activities of phenolic compounds isolated from Cynoglossum cheirifolium L.

In an extensive search for bioactive compounds from plant sources, the quantitative and qualitative characterisation of the compounds present in Cynoglossum cheirifolium extracts was studied. Total phenolic and flavonoid contents were determined by spectrophotometric techniques. In vitro antioxidant and radical scavenging profiling was determined through DPPH^? scavenging activity and Ferric reducing antioxidant power (FRAP). Our study showed that leaves produce more phenolic compounds, followed by flowering aerial part. The butanolic fraction obtained from leaves extract exhibited the highest total phenolics (78.65 ± 3.58 mg GAE/g DW) and flavonoids (22.15 ± 4.66 mg CE/g DW). In contrast, this fraction displayed the highest DPPH^? scavenging ability with IC₅₀ values of 0.06 ± 0.003 mg/mL. The RP-HPLC-PDA analysis of phenolic compounds from leaves of C. cheirifolium lets to identify: rosmarinic acid, ferulic acid, caffeic acid, p-coumaric acid, syringic acid, sinapic acid and rutin. The obtained results indicate that this plant represent a valuable source of natural antioxidants.     

A theoretical study on the antioxidant activity of Uralenol and Neouralenol scavenging two radicals

Uralenol and neouralenol are two typical licorice root extracts that presents multiple reactive hydroxyl groups, which are considered as good free radical scavengers. A theoretical study on the primary antioxidant activity of uralenol and neouralenol toward hydroxyl and hydroperoxyl radicals has been carried out using the density functional theory (DFT). A total of 10 reaction pathways of uralenol and neouralenol scavenging two radicals in gas phase and in water phase have been tracked. Neouralenol was found to be a better hydroxyl and hydroperoxyl scavenger than uralenol. In vivo, the more reactive sites in uralenol are U5 and U’1, respectively, for scavenging ·OH and ·OOH; and the more reactive sites in neouralenol are N4 and N’5 for scavenging ·OH and ·OOH, respectively.     

GC–MS Analysis of Hydrogen Sulfide,Carbonyl Sulfide,Methanethiol, Carbon Disulfide,Methyl Thiocyanate and Methyl Disulfide in Mainstream Vapor Phase Cigarette Smoke

A method is described for the simultaneous analysis of hydrogen sulfide, carbonyl sulfide, methanethiol, carbon disulfide, methyl thiocyanate and methyl disulfide in mainstream vapor phase (MVP) cigarette smoke by gas chromatography–mass spectrometry. The fresh MVP smoke was collected in a gas bag, followed by injection of a 50 μL gas sample into the GC inlet via an automatic six-port valve. The separation was on a CP-PoraPLOT Q column and MS was operated in SIM mode. It was found that while carbonyl sulfide and carbon disulfide are very stable in the gas bag, hydrogen sulfide, methanethiol, methyl disulfide and methyl thiocyanate are extremely reactive and their levels increase or decrease drastically with the storage time in the gas bag. These results suggest that there is an absolute need to analyze the smoke sample as quickly as possible. Maintaining a precise time after the smoke collection is a key factor in order to obtain reproducible results. In this study, all the samples are injected within 2 min after MVP smoke was collected in the bag. Under smoke conditions of 60 mL puff of 2 s duration every 30 s, 12 brands of commercial cigarettes and Kentucky Reference 2R4F cigarettes were analyzed. Average values of three replicates of the 2R4F cigarettes were 31.6 μg cigt^?1 hydrogen sulfide, 40.7 μg cigt^?1 carbonyl sulfide, 25.6 μg cigt^?1 methanethiol, 2.2 μg cigt^?1 carbon disulfide, 23.7 μg cigt^?1 methyl thiocyanate and 17.6 μg cigt^?1 methyl disulfide. All other types of analyzed cigarettes show a similar quantitative distribution for these analytes.     

Free radical scavenging and COX-2 inhibition by simple colon metabolites of polyphenols: A theoretical approach

Free radical scavenging and inhibitory potency against cyclooxygenase-2 (COX-2) by two abundant colon metabolites of polyphenols, i.e., 3-hydroxyphenylacetic acid (3-HPAA) and 4-hydroxyphenylpropionic acid (4-HPPA) were theoretically studied. Different free radical scavenging mechanisms are investigated in water and pentyl ethanoate as a solvent. By considering electronic properties of scavenged free radicals, hydrogen atom transfer (HAT) and sequential proton loss electron transfer (SPLET) mechanisms are found to be thermodynamically probable and competitive processes in both media. The Gibbs free energy change for reaction of inactivation of free radicals indicates 3-HPAA and 4-HPPA as potent scavengers. Their reactivity toward free radicals was predicted to decrease as follows: hydroxyl >> alkoxyls > phenoxyl ≈ peroxyls >> superoxide. Shown free radical scavenging potency of 3-HPAA and 4-HPPA along with their high μM concentration produced by microbial colon degradation of polyphenols could enable at least in situ inactivation of free radicals. Docking analysis with structural forms of 3-HPAA and 4-HPPA indicates dianionic ligands as potent inhibitors of COX-2, an inducible enzyme involved in colon carcinogenesis. Obtained results suggest that suppressing levels of free radicals and COX-2 could be achieved by 3-HPAA and 4-HPPA indicating that these compounds may contribute to reduced risk of colon cancer development.     

Determination of non-toxic and potentially toxic elements concentration and antioxidant capacity in selected natural and essential oils with high market values

Natural oils (NOs) and essential oils (EOs) are widely used in the food and beverage, medical, aromatherapy and cosmetic industries, but little is known about their elemental composition or antioxidant ability. Microwave-assisted acid digestion and inductively coupled plasma-optical emission spectroscopy were used to determine the non-toxic elements (Al, Ca, Cu, Fe, K, Mg, Na, Se and Zn) and potentially toxic elements (As, Cr, Cd, Mn, Ni and Pb) concentrations in 13 selected NOs and EOs. The per cent recoveries of laboratory-fortified blanks analysed for quality control were 94–110%. The elemental concentrations varied widely in NO and EO samples, as demonstrated by the large standard deviation obtained for some elements. The average levels of non-toxic elements (Al (14.5 ± 3.7 μg/g); Ca (278 ± 138 μg/g); Cu (7 ± 14 μg/g); Fe (16 ± 5 μg/g); K (36 ± 31 μg/g); Mg (56 ± 27 μg/g); Na (266 ± 277 μg/g); Se (0.7 ± 0.3 μg/g) and Zn (6.1 ± 2.6 μg/g)) were determined in NOs and EOs. Comparatively, low levels of potentially toxic elements (As (0.1 ± 0.2 μg/g); Cd (0.1 ± 0.0 μg/g); Cr (0.2 ± 0.1 μg/g); Mn (0.8 ± 0.1 μg/g); Ni (4.5 ± 2.2 μg/g); and Pb (0.3 ± 0.2 μg/g)) were obtained in the oils. Principal component analysis (PCA) revealed that the first two principal components explained 100% of the variability in the elemental concentrations. Na, Ca, Mg and K were the main contributors to PCA. Non-toxic element pairs were strongly correlated (R² > 0.9440) indicating a common source in these oils, but toxic element pairs were poorly correlated. Although toxic element concentrations were low, routine monitoring in oils is recommended. The antioxidant ability of NOs and EOs to potentially reduce free radicals, which are often involved in several degenerative diseases, such as ageing, stroke, diabetes and cancers was determined by DPPH (2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl) free radical scavenging assay and ultraviolet-visible spectroscopy. Jasmine, castor and tea tree lemon oils were the best antioxidants. The oils in this study have the potential to replace artificial antioxidants used in foods, cosmetics and other products.     

Analysis of Vinyl Chloride in Vapor Phase of Mainstream Cigarette Smoke by GC–MS Under ISO and Health Canada Intensive Machine Smoking Regimens

Vinyl chloride (VC) in the vapor phase of mainstream cigarette smoke was determined under both International Organization for Standardization (ISO) and Health Canada intensive (HCI) machine smoking regimens, which was suspected to be carcinogenic compound. VC was collected by passing the mainstream cigarette smoke through a Cambridge Filter Pad (CFP) into cryogenic traps containing methanol. The impinger solutions were fortified with VC-d ₃ and analyzed by GC–MS. Limits of detection for vinyl chloride was 0.9 ng mL^?1 with the recovery in the range of 93.2–98.4 %. Moreover, the intra-day and inter-day precision was 7.39 and 9.77 %, respectively. Under HCI machine smoking regimen, the vinyl chloride yields in vapor phase of mainstream cigarette smoke were much higher and the average increase was greater than 100 % compared with those under ISO smoking condition.     

Synthesis,crystal structures,antioxidant activities,and DNA-binding studies of two silver(I) complexes with 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane,and α,β-unsaturated carboxylates

Two new ternary complexes of silver(I) with 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane (bebt) and two ·α,β-unsaturated carboxylates, [Ag(bebt)(crotonate)] (1) and [Ag(bebt)₂](o-coumarate)·CH₃CN·2C₂H₅OH (2), have been synthesized, and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray diffraction revealed that the coordination environment of 1 can be described as trigonal planar, while 2 has a distorted tetrahedral geometry. Experimental studies of the DNA-binding properties indicated that the free ligand and both complexes bind to DNA via intercalation, and the order of the binding affinity is 1 > bebt > 2. Antioxidant activity experiments show that 2 possesses significant antioxidant activity against hydroxyl radicals, with more efficient hydroxy radical scavenging compared with mannitol and vitamin C.