Singlet Oxygen Oxidation Research Articles

Mechanism of lipid peroxidation of liposomes by cold atmospheric pressure plasma jet irradiation.

Liposome lipid peroxidation induced by cold atmospheric pressure plasma jet (CAPPJ) irradiation was investigated. The formation of thiobarbituric acid reactive substances (TBARS), an indicator of lipid peroxidation final products, as a function of irradiation was observed. Lipid radicals, peroxidation reaction intermediates generated by CAPPJ irradiation, were confirmed by increased NBD-pen fluorescence intensity. Additionally, lipid peroxidation products, liposomal phosphatidylcholine (PC) isomers, were analyzed by LC-MS/MS. Products specific to singlet oxygen (1O2) oxidation, 16:0/10-hydroperoxy-8E,12Z-octadecanoic acid (10-8E,12Z-HpODE) PC and 16:0/12-9E,13E-HpODE PC, were not detected, but radical oxidation specific products 16:0/13-9E,11E-HpODE PC and 16:0/9-10E,12E-HpODE PC were. This suggests that during CAPPJ irradiation, radicals, rather than 1O2, are the primary reactive species of lipid peroxidation. This is also supported by the β-carotene quenching of 1O2 not suppressing TBARS and lipid radical generation. Also, neither TBARS formation nor lipid radical generation were suppressed by SOD, indicating that the superoxide radical (O2 •-) is not responsible for the lipid peroxidation reaction. As the CAPPJ irradiation of water produces large quantities of hydroxyl radical (•OH) and •OH scavengers decreased the amount of TBARS produced by CAPPJ irradiation, it is highly plausible that •OH is the primary species involved in CAPPJ-induced liposome lipid peroxidation.

Excellent antibiotic degradation through PMS activation via bio derived Fe-Mn oxides with tunable defect concentration: Synergy between singlet oxygen oxidation and electron transfer

Regulating the defect sites and structural composition of metal-based metal catalysts is an effective strategy to improve the activity of activating PMS to degrade pollutants. Herein, bio derived Fe/Mn composite oxides (BFMO) rich in oxygen vacancy composed of crystalline manganese oxide coated with amorphous iron oxide was prepared through microbial mediation, and used for PMS activation in the degradation of tetracycline (TC). After 60 minutes reaction, the removal rate of TC achieved 92.4 %−98.8 % within wide pH range of 3–12. Besides, this system has outstanding anti-interference ability to common ions and humic acid (HA). The outstanding catalytic performance stemmed from the non-radical pathway for producing singlet oxygen (1O2) and electron transfer, facilitated by defect-rich polyvalent Mn and amorphous Fe species. Polyvalent Mn species accelerate the electron transfer process, and its surface defect structure further promotes the adsorption of pollutants on the surface of the materials. The redox cycle of Fe3+/Fe2+ was accelerate via electron-rich groups. This study explored the synergy triggered by microbe-mediated defect sites and structure-dependent, providing a design strategy for environmental remediation of PMS activated by Fe/Mn based bimetallic catalysts with strong resistance to environmental interference.

Crucial role of nitrogen vacancies in carbon activated persulfate toward nonradical abatement of micropollutants from secondary effluent

Biomass-derived carbonaceous materials exhibit fascinating potentials in nonradical oxidation of micropollutants (MPs) by activating persulfate and their performances mainly rest on graphitic N. However, the simultaneously derived N vacancy received little attention. Herein, a graphene-like material rich in N vacancy was synthesized from coffee residues. It showed excellent removal efficiency (95 %) and degradation kinetics (0.21 min−1) in abating tetracycline antibiotics from secondary effluent and significant biotoxicity was diminished. Solid nonradical oxidation consisting of electron transfer (89 %) and singlet oxygen (1O2) oxidation (11 %) was determined. By tracking 1O2 source and electron flow, ketone group appeared at N vacancy was found as the critical site to grab electrons from peroxydisulfate (PDS) with production of 1O2. Then the electrons were transferred to graphitic N driven by the microelectric field between them. This work notices the function of vacancies in biomass resources for high-efficient removal of MPs from real water matrix.

Highly stable carbon-coated nZVI composite Fe0@RF-C for efficient degradation of emerging contaminants

Nanoscale zerovalent iron (nZVI) has garnered significant attention as an efficient advanced oxidation activator, but its practical application is hindered by aggregation and oxidation. Coating nZVI with carbon can effectively addresses these issues. A simple and scalable production method for carbon-coated nZVI composite is highly desirable. The anti-oxidation and catalytic performance of carbon-coated nZVI composite merit in-depth research. In this study, a highly stable carbon-coated core-shell nZVI composite (Fe0@RF-C) was successfully prepared using a simple method combining phenolic resin embedding and carbothermal reduction. Fe0@RF-C was employed as a heterogeneous persulfate (PS) activator for degrading 2,4-dihydroxybenzophenone (BP-1), an emerging contaminant. Compared to commercial nZVI, Fe0@RF-C exhibited superior PS activation performance and oxidation resistance. Nearly 95% of BP-1 was removed within 10 min in the Fe0@RF-C/PS system. The carbon layer promotes the enrichment of BP-1 and accelerates its degradation through singlet oxygen oxidation and direct electron transfer processes. This study provides a straightforward approach for designing highly stable carbon-coated nZVI composite and elucidates the enhanced catalytic performance mechanism by carbon layers.

Dual single atomic Fe-Ni sites in N‑doped nanoporous carbon for high-efficiency potassium periodate activation toward pollutant abatement

Diatomic catalysts (DACs) with atomically isolated metal pairs hold the potential for activating potassium periodate (PI) in sustainable pollution control, yet their synthesis poses a significant challenge. In this study, Fe/Ni species anchored to a nitrogen-doped carbon as diatomic catalysts (FeNi-NC DACs) were precisely synthesized by direct carbonization of metal–organic frameworks (MOFs) assembled by Fe/Ni-doped ZnO nanoparticles and used for the effective decomposition of organic pollutants through PI activation. As anticipated, FeNi-NC exhibited superior catalytic properties due to the abundance of adjacent bimetallic active sites (Fe/Ni-Nx), rich doped nitrogen, high specific surface area, and electron transport conductivity, surpassing single-atom Fe-NC and Ni-NC, as well as nonmetallic NC catalysts. Free radical quenching, electron paramagnetic resonance, and electrochemical experiments have shown that the FeNi-NC/PI system can oxidize organic compounds through non-free radical oxidation pathways, including singlet oxygen (1O2) oxidation and mediated electron transfer processes. Electron transfer mediated by FeNi-NC/PI* complexes is the primary mechanism for organic oxidation. Additionally, the FeNi-NC catalyst demonstrated remarkable stability in both inorganic-containing and real water samples, as well as in continuous-flow microreactors. This study introduces a novel approach for designing highly efficient DACs and offers fundamental insights into the mechanism of PI-activated oxidation of organic pollutants.

Singlet Oxygen Formation Mechanism for the H2O2-Based Fenton-like Reaction Catalyzed by the Carbon Nitride Homojunction.

The singlet oxygen (1O2) oxidation process activated by metal-free catalysts has recently attracted considerable attention for organic pollutant degradation; however, the 1O2 formation remains controversial. Simultaneously, the catalytic activity of the metal-free catalyst limits the practical application. In this study, carbon nitride (HCCN) containing an intramolecular homojunction, a kind of metal-free catalyst, exhibits excellent activity compared to g-C3N4 (CN) and crystalline carbon nitride (HCN) for tetracycline hydrochloride degradation through the H2O2-based Fenton-like reaction. The rate constant for HCCN increased about 16.1 and 8.9 times than that of CN and HCN, respectively. The activity of HCCN was enhanced, and the dominant reactive oxygen species (ROS) changed from hydroxyl radicals (•OH) to 1O2 with an increase in pH from 4.5 to 11.5. A novel formation pathway of 1O2 was revealed. This result is different from the normal reference, in which •OH is always the primary ROS in the H2O2-based Fenton-like reaction. This study may provide a possible strategy for the investigation on the nonradical oxidation process in the Fenton-like reaction.

Bifunctionality of dirhodium tetracarboxylates in metallaphotocatalysis

Metallaphotocatalysis has been recognized as a pivotal catalysis enabling new reactivities. Traditional metallaphotocatalysis often requires two or more separate catalysts and exhibits flaw in cost and substrate-tolerance, thus representing an await-to-solve issue in catalysis. We herein realize metallaphotocatalysis with a bifunctional dirhodium tetracarboxylate ([Rh2]) alone. The [Rh2] shows an photocatalytic activity of promoting singlet oxygen (1O2) oxidation. By harnessing its photocatalytic activity, the [Rh2] catalyzes a photochemical cascade reaction (PCR) via combination of carbenoid chemistry and 1O2 chemistry. The PCR is characterized by high atom-efficiency, excellent stereoselectivities, mild conditions, scalable synthesis, and pharmaceutically interesting products. DFT calculations-aided mechanistic study rationalizes the reaction pathway and interprets the origin of stereoselectivities of the PCR. The products show inhibitory activity against PTP1B, being promising in the treatment of type II diabetes and cancers. Overall, here we show the bifunctional [Rh2] merges Rh-carbenoid chemistry and 1O2 chemistry.

Periodate-Mediated Aerobic Oxidation of Sulfides over a Bifunctional Porphyrin-polyoxometalate Catalyst: Photosensitized Singlet Oxygen Oxidation of Iodate to Periodate.

Regeneration of terminal oxidants by molecular oxygen in metal-catalyzed oxidations of organic substrates has the advantage of avoiding the use of stoichiometric amounts of hazardous and/or expensive reagents to meet (some of) the green chemistry requirements. In the present study, photosensitized singlet oxygen oxidation of iodate to periodate has been used to regenerate the oxidant in polyoxometalate (POM)-catalyzed oxidation of sulfides to sulfoxides with periodate in water. To the best of our knowledge, it is the first report on singlet oxygen oxidation of iodate to periodate. In order to determine the contribution of photooxidation and oxidation pathways in the formation of sulfoxide, the oxidation of diphenyl sulfide with a very low reactivity toward aerobic photooxidation was studied; a sevenfold increase in the conversion of the sulfide to the diphenyl sulfoxide was observed for the reaction conducted in the presence of H2TMPyP-PW12O40/IO3-/O2/hν compared to that in the presence of H2TMPyP-PW12O40/O2/hν. Also, under the same conditions, a ca. 1.5-fold increase was observed in the case of methyl phenyl sulfide, which shows high reactivity toward both the oxidation and photooxidation reactions. A porphyrin-POM nanocomposite formed by the electrostatic immobilization of meso-tetra(N-methylpyridinium-4-yl)porphyrin (H2TMPyP) on PW12O40 was employed for the one-pot oxidation and photooxidation reactions. Field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), diffuse-reflectance UV-vis spectroscopy, thermal gravimetric analysis, and Fourier transform infrared were used to characterize the formation of the hybrid compound. An average particle size of 42 nm was estimated for H2TMPyP-PW12O40 from XRD peak broadening using the Scherrer equation. Also, FESEM images showed the formation of nearly spherical nanoparticles with a size of ca. 200 nm. The redshift of the Soret band of H2TMPyP upon immobilization on POM was attributed to strong N-H···O hydrogen-bond interactions between POM and porphyrin.

The Antioxidant Ability and Extraction Yield of Beta Carotene

Beta carotene (β-Carotene), one of the most abundant carotenoids in fruit and vegetables, is an essential source of antioxidants. The antioxidation ability of β-Carotene has been through in vitro and in vivo tests, which proved that the compound could prevent the oxidation of singlet and triplet oxygen, oil, and fats. Since β-Carotene is unstable and prone to oxidation when exposed to high temperature and high light intensity, various extraction methods have been tested and applied to get to the maximised yield and purity of the extract. Among all the extraction methods, enzyme-assisted extraction (EAE) is the most efficient, with almost 100% extraction yield. The need for antioxidants by the public promoted the production of β-Carotene nutraceuticals and cosmetics. This essay compared the efficacy of different extraction methods and bioactivity of β-Carotene in different research papers and concluded the extraction method with the highest efficiency.

Coupled radical and nonradical activation of peroxymonosulfate by the piezo-photocatalytic effect of α-SnWO4/ZnO heterojunction to boost the degradation and detoxification of carbamazepine

Piezo-photocatalytic processes based on heterogeneous catalysts, by establishing electronic fast track to realize electronic storage and conversion, are proved to be effective ways to improve the efficiency of PMS activation. Herein, α-SnWO4/ZnO catalyst with p-n heterojunction was constructed to testify the piezo-photocatalytic effect on peroxymonosulfate (PMS) activation for pollution control. The decomposition rate of carbamazepine (CBZ) in the piezo-photocatalytic PMS activation process by α-SnWO4/ZnO heterojunction was 12.6 and 5.2 times to that by ZnO and α-SnWO4 processes, respectively. In addition, the total organic carbon (TOC) removal rate of CBZ reached 89%, and TOC in the actual water body was also effectively removed. Free radical quenching and detection experiments showed that nonradicals (1O2) and free radicals (O2−, OH) were the mainly active species of the process, by which the toxicity of the intermediates of CBZ was significantly reduced by the combination of the radical and nonradical pathways through hydroxylation and singlet oxygen oxidation. Furthermore, the influences of the experimental factors, including the initial pH, PMS concentration, temperature and reuse of catalysts on CBZ degradation were evaluated. Notably, the activation energy (Ea) in this work was calculated as 34.2 kJ mol−1, which was lower than that of other reported systems. Overall, this work can scientifically guide the design of high-performance piezo-photocatalysts to use common metals for efficient activation of PMS as economical alternatives over expensive rare metal catalysts for water purification.

Preparation of NDI-BODIPY Based Photo Catalyzers for Green LED Irradiated Synthesis of Juglone.

Photochemistry related studies have been driven by with the application of new types of photocatalysis. Lately boron-dipyrromethene(BODIPY) as distinguished chromophore with exceptional photophysical and chemical features has emerged as a viable photosensitizer. Within this context, three new NDI-BODIPY triads (8-10) were synthesized/ characterized and used to investigate the efficiencies of singlet oxygen generation and oxidation of 1,5-dihydroxynapthalene to juglone under visible light. Singlet oxygen generation was determined both via indirect method by using 1,3-diphenylisobenzofuran as trap molecule and from the characteristic 1O2 phosphorescence at 1270nm. Also, NDI with BODIPY dyes bearing bromine and iodine atoms were shown to be highly active photocatalysts in which the activities are comparable or higher to the readily available commercial systems where 36% (9) and 66% (10) juglone production was achieved under 15min. This work may emphasize good example of applying NDI-BODIPY based triads as photocatalysts for a series of important organic transformations.

Removal of Bisphenol A via peroxymonosulfate activation over graphite carbon nitride supported NiCx nanoclusters catalyst: Synergistic oxidation of high-valent nickel-oxo species and singlet oxygen.

In this work, a g-C3N4 supported NiCx nanoclusters catalyst (NiCx-CN) was developed, and its performance in activating peroxymonosulfate (PMS) was evaluated. Mechanism investigation stated that although singlet oxygen (1O2) was formed in the catalytic process, its contribution to BPA elimination was weeny. Interestingly, through the experiment with dimethyl sulfoxide as the probe, it was considered that the high-valent nickel-oxo species (Ni&+=O), generated after the interaction of NiCx-CN and PMS, was the dominating reactive oxygen species (ROS). Theoretical calculations (DFT) implied that NiCx-CN might lose electrons to generate high-valent Ni, which was consistent with the detection of Ni3+ on the surface of the used NiCx-CN. Besides, the prepared NiCx-CN showed advantages in resisting the interference of inorganic anions. Meanwhile, three BPA degradation routes had been proposed based on the transformation intermediates. This study will establish a new protocol for PMS activation using heterogeneous Ni-based catalysts to efficiently degrade organic pollutants via a nonradical mechanism.

Practical Aspects in the Study of Biological Photosensitization Including Reaction Mechanisms and Product Analyses: A Do's and Don'ts Guide†.

The interaction of light with natural matter leads to a plethora of photosensitized reactions. These reactions cause the degradation of biomolecules, such as DNA, lipids, proteins, being therefore detrimental to the living organisms, or they can also be beneficial by allowing the treatment of several diseases by photomedicine. Based on the molecular mechanistic understanding of the photosensitization reactions, we propose to classify them in four processes: oxygen-dependent (type I and type II processes) and oxygen-independent [triplet-triplet energy transfer (TTET) and photoadduct formation]. In here, these processes are discussed by considering a wide variety of approaches including time-resolved and steady-state techniques, together with solvent, quencher, and scavenger effects. The main aim of this survey is to provide a description of general techniques and approaches that can be used to investigate photosensitization reactions of biomolecules together with basic recommendations on good practices. Illustration of the suitability of these approaches is provided by the measurement of key biomarkers of singlet oxygen and one-electron oxidation reactions in both isolated and cellular DNA. Our work is an educational review that is mostly addressed to students and beginners.

Analysis of docosahexaenoic acid hydroperoxide isomers in mackerel using liquid chromatography–mass spectrometry

Docosahexaenoic acid (DHA) is mostly esterified in food and is easily oxidized by exposure to heat or light. Hydroperoxide positions of DHA mono-hydroperoxide (DHA;OOH) provide information on oxidation mechanisms (e.g., radical- or singlet oxygen oxidation), yet direct identification of esterified DHA;OOH isomers has not been achieved. We previously accomplished the direct analysis of free DHA;OOH isomers with liquid chromatography-mass spectrometry (LC–MS/MS). In this study, we developed an LC–MS/MS method for direct analysis of esterified DHA;OOH based on our previous study. The developed method was capable of distinguishing esterified DHA;OOH isomers in raw- and oxidized mackerel. The result suggested that radical oxidation of esterified DHA can progress even in refrigeration. Different transitions were observed depending on the oxidation mechanism and lipid class. The analytical method and insights obtained in this study would be valuable to further understand and effectively prevent DHA oxidation in food products.

Ozone Micronano-bubble-Enhanced Selective Degradation of Oxytetracycline from Production Wastewater: The Overlooked Singlet Oxygen Oxidation.

The efficient and selective removal of refractory antibiotics from high-strength antibiotic production wastewater is crucial but remains a substantial challenge. In this study, a novel ozone micronano-bubble (MNB)-enhanced treatment system was constructed for antibiotic production wastewater treatment. Compared with conventional ozone, ozone MNBs exhibit excellent treatment efficiency for oxytetracycline (OTC) degradation and toxicity decrease. Notably, this study identifies the overlooked singlet oxygen (1O2) for the first time as a crucial active species in the ozone MNB system through probe and electron paramagnetic resonance methods. Subsequently, the oxidation mechanisms of OTC by ozone MNBs are systematically investigated. Owing to the high reactivity of OTC toward 1O2, ozone MNBs enhance the selective and anti-interference performance of OTC degradation in raw OTC production wastewater with complex matrixes. This study provides insights into the mechanism of ozone MNB-enhanced pollutant degradation and a new perspective for the efficient treatment of high-concentration industrial wastewater using ozone MNBs. In addition, this study presents a promising technology with scientific guidance for the treatment of antibiotic production wastewater.

Boosting the photocatalytic performance of the oligo (phenylene vinylene) moiety by copolymerization for the heterogeneous degradation of indigo carmine dye

Abstract The copolymerization with flexible and rigid spacers of 4,4’-((1E, 1′E)-(2,5-dimethoxy-1,4-phenylene)bis (ethene-2,1-diyl))dibenzoic acid, as a promising phenylene vinylene-based (PV) organic photocatalyst, was examined as a strategy to validate the effect of such chemical modifications in the modulation of the photocatalytic properties of this organic π-conjugated moiety. The polymers prepared here were fully characterized and evaluated as photocatalysts in the degradation of indigo carmine dye under two different irradiation scenarios (UVA and visible), consistently displaying a superior efficiency in contrast to their monomeric oligo (phenylene vinylene) (OPV) counterparts. Scavenging experiments confirmed that photocatalysis proceeds via the generation of superoxide radicals (O2 •–), singlet oxygen (1O2), and direct oxidation. The obtained results proved that the insertion of an aromatic rigid spacer not only prompts an enhancement in the photocatalytic activity of the phenylene vinylene-based polymers but also increases the stability of the OPV moiety by minimizing the reaction of the vinyl fragments with reactive oxygen species. This was demonstrated with the reuse experiments, where 96% of the photocatalytic activity was preserved throughout the first five reuse cycles.

Co-doped Fe3O4/α-FeOOH for highly efficient peroxymonosulfate activation to degrade trimethoprim: Occurrence of hybrid non-radical and radical pathways

Trimethoprim (TMP), as a widely used chemotherapeutic antibiotic agent, has caused potential risks to the aquatic environment. In this study, magnetic Co-doped Fe3O4/α-FeOOH was fabricated by a facile one-step ageing method and used for activation of peroxymonosulfate (PMS) in TMP degradation. It was found that low catalyst (0.5 g/L) and PMS addition (0.2 mM) led to the high degradation efficiency of TMP (97.2%, kobs = 0.11211 min−1) over a wide range of pH. The oxidation of active radical (SO4·−) and non-radical singlet oxygen (1O2) co-acted on TMP degradation. Besides, PMS was activated through the cycles between Co(II)/Co(III) and Fe(II)/Fe(III). Fifteen degradation intermediates of TMP were identified by LC-MS, and three possible degradation pathways including hydroxylation, demethylation, and cleavage were proposed. The recovered catalysts exhibited high stability and reusability, maintaining 80% TMP removal efficiency with inappreciable metal leaching (0.012 mg/L of Co, 0.113 mg/L of Fe) after six cycles. Besides, the Co–Fe3O4/α-FeOOH/PMS system was highly tolerant to inorganic anions and actual water bodies (river water, lake water, tap water, and sewage plant effluent). Overall, this work provided a promising way to the potential application of Fe-based binary metal oxide for PMS activation.

Elucidation of Olive Oil Oxidation Mechanisms by Analysis of Triacylglycerol Hydroperoxide Isomers Using LC-MS/MS.

Despite the importance of the insight about the oxidation mechanisms (i.e., radical and singlet oxygen (1O2) oxidation) in extra virgin olive oil (EVOO), the elucidation has been difficult due to its various triacylglycerol molecular species and complex matrix. This study tried to evaluate the mechanisms responsible for EVOO oxidation in our daily use by quantitative determination of triacylglycerol hydroperoxide (TGOOH) isomers using LC-MS/MS. The standards of dioleoyl-(hydroperoxy octadecadienoyl)-triacylglycerol and dioleoyl-(hydroperoxy octadecamonoenoyl)-triacylglycerol, which are the predominant TGOOHs contained in EVOO, were prepared. Subsequently, fresh, thermal-, and photo-oxidized EVOO were analyzed. The obtained results mostly agreed with the previously reported characteristics of the radical and 1O2 oxidation of linoleic acid and oleic acid. This suggests that the methods described in this paper should be valuable in understanding how different factors that determine the quality of EVOO (e.g., olive species, cultivation area, cultivation timing, and extraction methods) contribute to its oxidative stability.

Insights into singlet oxygen generation and electron-transfer process induced by a single-atom Cu catalyst with saturated Cu-N4 sites

SummaryPersulfate-based nonradical oxidation processes are appealing in water treatment for the efficient and selective degradation of trace contaminants in complex water matrices. However, there is still lacking of systematic understanding of the relationship between multiple nonradical pathways and the active sites of catalyst. Herein, a single-atom Cu catalyst with saturated Cu-N4 sites on a carbon substrate (SA-Cu-NC) was constructed to activate peroxymonosulfate (PMS), which exhibited high catalytic performance and selectivity for pollutant degradation in different water conditions. Combined with the results of density functional theory (DFT) calculations, the electron-rich area around Cu site and the electron-poor area around C site in the saturated Cu-N4 configuration could efficiently adsorb and activate PMS, which promoted pollutant degradation through the oxidation of singlet oxygen (1O2) and electron transfer process, respectively. This study advances the understanding of the saturated coordination structure of metals and the superiority of multiple nonradical pathways in wastewater treatment.

Determination of acrolein generation pathways from linoleic acid and linolenic acid: increment by photo irradiation

2-Propenal (acrolein) is a toxic aldehyde generated from the thermal degradation of edible oils. While previous studies have suggested that linolenic acid (LnA) is the origin of acrolein formation in edible oils, these studies were performed under thermal conditions where only the fatty acid hydroperoxide (FAOOH) isomers derived from radical oxidation were formed. In this study, we reinvestigated the acrolein generation pathway through another oxidation mechanism involving singlet oxygen (1O2) oxidation (type II photo-oxidation). Standards of the main FAOOH isomers (oleic acid hydroperoxide, linoleic acid hydroperoxide (HpODE), and linolenic acid hydroperoxide (HpOTE)) found in edible oils were prepared, and their decomposition products, including those derived from1O2 oxidation (i.e., 10- and 12-HpODE) were analyzed by GC-EI-MS. We found that 1O2 oxidation products of linoleic acid (LA) and LnA but not OA, are significant sources of acrolein formation. The amount of acrolein formed from edible oils high in LA (e.g., rice bran oil) increased by photo irradiation. Further investigation into the mechanism of acrolein generation demonstrated that the amount of acrolein derived from 1O2 oxidation-specific HpOTE isomers (i.e., 10- and 15-HpOTE) was two times greater than that of other HpOTE isomers (i.e., 9-, 12-, 13-, and 16-HpOTE). The results of the present study provide a new pathway of acrolein formation from type II photo-oxidation. This information can be used to inform on oil storage and processing conditions to reduce exposure and dietary intake of acrolein.