Singlet Oxygen Scavenger Research Articles

Geometrical isomers of lutein and fucoxanthin: Unveiling their antioxidant potentials and skin-related biological activities

Although carotenoids are most commonly found in dietary sources as all-E-isomers, some carotenoids accumulate in the skin as Z-isomers; their roles are largely unknown. This study investigated the effects of E/Z-isomers of lutein and fucoxanthin, two xanthophyll carotenoids, on their antioxidant potential and skin-related biological activities. Evaluation of ultraviolet (UV)-blocking abilities demonstrated the superior performance of Z-isomer-rich lutein and fucoxanthin against UV-A and UV-B radiation, with Z-isomer-rich lutein exhibiting higher UV-B protection. Antioxidant assays revealed that all-E- and Z-isomer-rich lutein and fucoxanthin had potent singlet oxygen and hydroxyl radical scavenging activities. Moreover, Z-isomer-rich lutein and fucoxanthin exhibited enhanced lipid peroxidation scavenging compared with their all-E counterparts. Both isomers of lutein and fucoxanthin exhibited potent skin-antiaging and skin-whitening effects in several in vitro assays, including anti-elastase and anti-tyrosinase activities. These findings suggest that geometric isomers may enhance the therapeutic efficacy of carotenoids in skin care applications.

Osmotic stress in roots drives lipoxygenase-dependent plastid remodeling through singlet oxygen production.

Osmotic stress, caused by the lack of water or by high salinity, is a common problem in plant roots. Osmotic stress can be reproducibly simulated with the application of solutions of the high-molecular-weight and impermeable polyethylene glycol. The accumulation of different reactive oxygen species, such as singlet oxygen, superoxide, and hydrogen peroxide, accompany this stress. Among them, singlet oxygen, produced as a byproduct of lipoxygenase activity, has been associated with limiting root growth. To better understand the source and effect of singlet oxygen, we followed its production at the cellular level in Arabidopsis (Arabidopsis thaliana). Osmotic stress initiated profound changes in plastid and vacuole structure. Confocal and electron microscopy showed that the plastids were a source of singlet oxygen accompanied by the appearance of multiple, small extraplastidic bodies that were also an intense source of singlet oxygen. A marker protein, CRUMPLED LEAF, indicated that these small bodies originated from the plastid outer membrane. Remarkably, LINOLEATE 9S-LIPOXYGENASE 5, (LOX5), was shown to change its distribution from uniformly cytoplasmic to a more clumped distribution together with plastids and the small bodies. In addition, oxylipin products of type 9 lipoxygenase increased, while products of type 13 lipoxygenases decreased. Inhibition of lipoxygenase by the SHAM inhibitor or in down-regulated lipoxygenase lines prevented cells from initiating the cellular responses, leading to cell death. In contrast, singlet oxygen scavenging halted terminal cell death. These findings underscore the reversible nature of osmotic stress-induced changes, emphasizing the pivotal roles of lipoxygenases and singlet oxygen in root stress physiology.

Senescence Rejuvenation through Reduction in Mitochondrial Reactive Oxygen Species Generation by Polygonum cuspidatum Extract: In Vitro Evidence.

Oxidative stress caused by reactive oxygen species (ROS) is one of the major causes of senescence. Strategies to reduce ROS are known to be important factors in reversing senescence, but effective strategies have not been found. In this study, we screened substances commonly used as cosmetic additives to find substances with antioxidant effects. Polygonum cuspidatum (P. cuspidatum) extract significantly reduced ROS levels in senescent cells. A novel mechanism was discovered in which P. cuspidatum extract reduced ROS, a byproduct of inefficient oxidative phosphorylation (OXPHOS), by increasing OXPHOS efficiency. The reduction in ROS by P. cuspidatum extract restored senescence-associated phenotypes and enhanced skin protection. Then, we identified polydatin as the active ingredient of P. cuspidatum extract that exhibited antioxidant effects. Polydatin, which contains stilbenoid polyphenols that act as singlet oxygen scavengers through redox reactions, increased OXPHOS efficiency and subsequently restored senescence-associated phenotypes. In summary, our data confirmed the effects of P. cuspidatum extract on senescence rejuvenation and skin protection through ROS reduction. This novel finding may be used as a treatment in senescence rejuvenation in clinical and cosmetic fields.

Characterization, stability, and skin application of astaxanthin particulates

PurposeAstaxanthin (AX), commonly used for dermal applications, exhibits anti-inflammatory and antioxidant activities; however, it has poor water solubility. In this study, we investigated the physicochemical properties of AX-containing particulates formulated using the amphiphilic graft copolymer Soluplus (polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer: Sol) and polyethylene glycol-2000 (PEG 2000); in addition, the stability and skin applications of AX particulates were investigated.MethodsAX, Sol, and PEG were mixed by weight to prepare AX particles using the hydration method. The prepared particles were subjected to stability evaluations including particle size distribution, zeta potential estimation, and fluorescence spectroscopy as well as physical evaluations including 1H-1H NOESY NMR spectral measurement, powder X-ray diffraction, and differential scanning calorimetry. Functional evaluations included singlet oxygen scavenging, skin permeation test, and fluorescence microscopy.ResultsRelatively stable particles of Sol/AX and Sol/PEG 2000/AX, approximately 100 nm and 125 nm in size, respectively, were formed at a mixed weight ratio (9/1) of 0.1 M Ascorbic Acid solution (0.1 M ASC) and a mixed weight ratio (8/1/1) of 0.1 M ASC, respectively, at 25 °C after storage for 14 days under light-shielded condition. Stability evaluations revealed a decrease in fluorescence intensity and color fading for Sol/AX = 9/1 and Sol/PEG 2000/AX = 8/1/1 (dispersion medium: distilled water); however, no change in fluorescence intensity of AX was observed immediately after preparation in Sol/AX = 9/1 and Sol/PEG 2000/AX = 8/1/1 (dispersion medium: 0.1 M ASC). The fluorescence intensity of AX did not fluctuate significantly immediately after adjustment, and the particles remained stable, showing a bright orange color with time. NMR spectra of Sol/AX = 9/1 and Sol/PEG 2000/AX (dispersion medium: 0.1 M ASC) showed the interactions between the CH3 group e from Sol (1.8 ~ 2.0 ppm) and the CH groups H-15,11 from AX (6.7 ~ 6.8 ppm), 8’,12’ (6.4 ~ 6.5 ppm), H-10,14 (6.4 ~ 6.5 ppm), and 7,7’ (6.2 ~ 6.3 ppm), indicating the disappearance of cross peaks. Furthermore, new cross peaks were identified for the CH3 group e of Sol (1.8 ~ 2.0 ppm), the 7-membered ring z of Sol (1.5 ~ 1.8 ppm), the 5-membered ring S of ASC (3.5 ~ 3.6 ppm), the CH group T (3.8 ~ 3.9 ppm), and the CH group U (4.7 ppm). Fluorescence microscopy observations of microparticles formulated with Sol/PEG 2000/AX showed a slight improvement in skin penetration.ConclusionNew AX particulates were formed using Sol/PEG 2000/AX = 8/1/1, suggesting that Sol/PEG 2000/AX maintained the stability and improved the skin penetration of AX.

Dual Roles of the Photooxidation of Organic Amines for Enhanced Triplet-Triplet Annihilation Upconversion in Nanoparticles.

Oxygen-mediated triplet-triplet annihilation upconversion (TTA-UC) quenching limits the application of such organic upconversion materials. Here, we report that the photooxidation of organic amines is an effective and versatile strategy to suppress oxygen-mediated upconversion quenching in both organic solvents and aqueous solutions. The strategy is based on the dual role of organic amines in photooxidation, i.e., as singlet oxygen scavengers and electron donors. Under photoexcitation, the photosensitizer sensitizes oxygen to produce singlet oxygen for the oxidation of alkylamine, reducing the oxygen concentration. However, photoinduced electron transfer among photosensitizers, organic amines, and oxygen leads to the production of superoxide anions that suppress TTA-UC. To observe oxygen-tolerating TTA-UC, we find that alkyl secondary amines can balance the production of singlet oxygen and superoxide anions. We then utilize polyethyleneimine (PEI) to synthesize amphiphilic polymers to encapsulate TTA-UC pairs for the formation of water-dispersible, ultrasmall, and multicolor-emitting TTA-UC nanoparticles.

PEGylated chitosan-coated nanophotosensitizers for effective cancer treatment by photothermal-photodynamic therapy combined with glutathione depletion

The combination of photothermal therapy (PTT) and photodynamic therapy (PDT) has emerged as a promising strategy for cancer treatment. However, the poor photostability and photothermal conversion efficiency (PCE) of organic small-molecule photosensitizers, and the intracellular glutathione (GSH)-mediated singlet oxygen scavenging largely decline the antitumor efficacy of PTT and PDT. Herein, a versatile nanophotosensitizer (NPS) system is developed by ingenious incorporation of indocyanine green (ICG) into the PEGylated chitosan (PEG-CS)-coated polydopamine (PDA) nanoparticles via multiple π-π stacking, hydrophobic and electrostatic interactions. The PEG-CS-covered NPS showed prominent colloidal and photothermal stability as well as high PCE (ca 62.8 %). Meanwhile, the Michael addition between NPS and GSH can consume GSH, thus reducing the GSH-induced singlet oxygen scavenging. After being internalized by CT26 cells, the NPS under near-infrared laser irradiation produced massive singlet oxygen with the aid of thermo-enhanced intracellular GSH depletion to elicit mitochondrial damage and lipid peroxide formation, thus leading to ferroptosis and apoptosis. Importantly, the combined PTT and PDT delivered by NPS effectively inhibited CT26 tumor growth in vivo by light-activated intense hyperthermia and redox homeostasis disturbance. Overall, this work presents a new tactic of boosting antitumor potency of ICG-mediated phototherapy by PEG-CS-covered NPS.

Research progress on carotenoid production by Rhodosporidium toruloides.

Carotenoids are natural lipophilic pigments, which have been proven to provide significant health benefits to humans, relying on their capacity to efficiently scavenge singlet oxygen and peroxyl radicals as antioxidants. Strains belonging to the genus Rhodosporidium represent a heterogeneous group known for a number of phenotypic traits including accumulation of carotenoids and lipids and tolerance to heavy metals and oxidative stress. As a representative of these yeasts, Rhodosporidium toruloides naturally produces carotenoids with high antioxidant activity and grows on a wide variety of carbon sources. As a result, R. toruloides is a promising host for the efficient production of more value-added lipophilic compound carotenoids, e.g., torulene and torularhodin. This review provides a comprehensive summary of the research progress on carotenoid biosynthesis in R. toruloides, focusing on the understanding of biosynthetic pathways and the regulation of key enzymes and genes involved in the process. Moreover, the relationship between the accumulation of carotenoids and lipid biosynthesis, as well as the stress from diverse abiotic factors, has also been discussed for the first time. Finally, several feasible strategies have been proposed to promote carotenoid production by R. toruloides. It is possible that R. toruloides may become a critical strain in the production of carotenoids or high-value terpenoids by genetic technologies and optimal fermentation processes. KEY POINTS: • Biosynthetic pathway and its regulation of carotenoids in Rhodosporidium toruloides were concluded • Stimulation of abiotic factors for carotenoid biosynthesis in R. toruloides was summarized • Feasible strategies for increasing carotenoid production by R. toruloides were proposed.

Synthesis and singlet oxygen generation of boron-2-(4,5-dibromo-1H-imidazole-2-yl)-3,5-dipyrazolopyridine complex for antimicrobial photodynamic therapy.

In this study, the pyridine side of a boron 2-(2'-pyridyl) imidazole (BOPIM) core, which has very few derivatives synthesized in the literature and can show fluorescence properties in solid form, was derivatized with 1-methylpyrazole, predicted to have activity against fungi or bacteria according to the literature. Additionally, its imidazole side was brominated to increase the efficiency of singlet oxygen production by increasing the intersystem crossing. The photophysical properties of the new synthesized BOPIM derivative were investigated in general organic solvents with different polarities. While the wavelength of the maximum absorbance was determined as 406 nm in CH2Cl2 and THF, the wavelength of the highest emission was measured at 497 nm in CH3CN solvent. The largest Stokes shift was determined as 104 nm in CH3CN. This value was considerably higher than those of many photosensitizers. The singlet oxygen generation potential of the BOPIM derivative was revealed using a 440-nm LED lamp in the presence of singlet oxygen scavenger 1,3-diphenylisobenzofuran (DPBF). Additionally, it was demonstrated that the BOPIM derivative had no toxic effects by measurements made in the dark.

Exploring a Mitochondria Targeting, Dinuclear Cyclometalated Iridium (III) Complex for Image-Guided Photodynamic Therapy in Triple-Negative Breast Cancer Cells.

Photodynamic therapy (PDT) has emerged as an efficient and noninvasive treatment approach utilizing laser-triggered photosensitizers for combating cancer. Within this rapidly advancing field, iridium-based photosensitizers with their dual functionality as both imaging probes and PDT agents exhibit a potential for precise and targeted therapeutic interventions. However, most reported classes of Ir(III)-based photosensitizers comprise mononuclear iridium(III), with very few examples of dinuclear systems. Exploring the full potential of iridium-based dinuclear systems for PDT applications remains a challenge. Herein, we report a dinuclear Ir(III) complex (IRDI) along with a structurally similar monomer complex (IRMO) having 2-(2,4-difluorophenyl)pyridine and 4'-methyl-2,2'-bipyridine ligands. The comparative investigation of the mononuclear and dinuclear Ir(III) complexes showed similar absorption profiles, but the dinuclear derivative IRDI exhibited a higher photoluminescence quantum yield (Φp) of 0.70 compared to that of IRMO (Φp = 0.47). Further, IRDI showed a higher singlet oxygen generation quantum yield (Φs) of 0.49 compared to IRMO (Φs = 0.28), signifying the enhanced potential of the dinuclear derivative for image-guided photodynamic therapy. In vitro assessments indicate that IRDI shows efficient cellular uptake and significant photocytotoxicity in the triple-negative breast cancer cell line MDA-MB-231. In addition, the presence of a dual positive charge on the dinuclear system facilitates the inherent mitochondria-targeting ability without the need for a specific targeting group. Subcellular singlet oxygen generation by IRDI was confirmed using Si-DMA, and light-activated cellular apoptosis via ROS-mediated PDT was verified through various live-dead assays performed in the presence and absence of the singlet oxygen scavenger NaN3. Further, the mechanism of cell death was elucidated by an annexin V-FITC/PI flow cytometric assay and by investigating the cytochrome c release from mitochondria using Western blot analysis. Thus, the dinuclear complex designed to enhance spin-orbit coupling with minimal excitonic coupling represents a promising strategy for efficient image-guided PDT using iridium complexes.

Astaxanthin protects human ARPE-19 retinal pigment epithelium cells from blue light-induced phototoxicity by scavenging singlet oxygen

Age-related macular degeneration (AMD) is one of an increasing number of diseases that causes irreversible impairment and loss of vision in the elderly. AMD occurs by oxidative stress-mediated apoptosis of retinal pigment epithelium cells. The onset of AMD may be positively correlated with the exposure to blue light. We screened food-derived carotenoids for cytoprotective action against blue light irradiation using human ARPE-19 retinal pigment epithelium cells. This study revealed that blue light irradiation triggered apoptosis and oxidative stress in all-trans-retinal (atRAL)-exposed ARPE-19 cells by generating singlet oxygen (1O2), leading to significant cell death. We found that astaxanthin, a potent anti-oxidative xanthophyll abundant in several marine organisms including microalgae, salmon, and shrimp, significantly suppresses blue light-induced apoptotic cell death of atRAL-exposed ARPE-19 cells by scavenging 1O2. Mechanistic studies using the blue-light irradiated cells also demonstrated that the cytoprotective effects of astaxanthin can be attributed to scavenging of 1O2 directly. Our results suggest the potential value of astaxanthin as a dietary strategy to prevent blue light-induced retinal degeneration including AMD.

Assessing the Efficacy of A Mo2C/Peroxydisulfate System for Tertiary Wastewater Treatment: A Study of Losartan Degradation, E. coli Inactivation, and Synergistic Effects

This work examines the use of pristine Mo2C as an intriguing sodium persulfate (SPS) activator for the degradation of the drug losartan (LOS). Using 500 mg/L Mo2C and 250 mg/L SPS, 500 μg/L LOS was degraded in less than 45 min. LOS decomposition was enhanced in acidic pH, while the apparent kinetic constant decreased with higher LOS concentrations. According to experiments conducted in the presence of scavengers of reactive species, sulfate radicals, hydroxyl radicals, and singlet oxygen participated in LOS oxidation, with the latter being the predominant reactive species. The presence of competitors such as bicarbonate and organic matter reduced the observed efficiency in actual matrices, while, interestingly, the addition of chloride accelerated the degradation rate. The catalyst showed remarkable stability, with complete LOS removal being retained after five sequential experiments. The system was examined for simultaneous LOS decomposition and elimination of Escherichia coli. The presence of E. coli retarded LOS destruction, resulting in only 30% removal after 3 h, while the system was capable of reducing E. coli concentration by 1.23 log. However, in the presence of simulated solar irradiation, E. coli was reduced by almost 4 log and LOS was completely degraded in 45 min, revealing a significant synergistic effect of the solar/Mo2C/SPS system.

Sedation Therapy in Intensive Care Units: Harnessing the Power of Antioxidants to Combat Oxidative Stress.

In critically ill patients requiring intensive care, increased oxidative stress plays an important role in pathogenesis. Sedatives are widely used for sedation in many of these patients. Some sedatives are known antioxidants. However, no studies have evaluated the direct scavenging activity of various sedative agents on different free radicals. This study aimed to determine whether common sedatives (propofol, thiopental, and dexmedetomidine (DEX)) have direct free radical scavenging activity against various free radicals using in vitro electron spin resonance. Superoxide, hydroxyl radical, singlet oxygen, and nitric oxide (NO) direct scavenging activities were measured. All sedatives scavenged different types of free radicals. DEX, a new sedative, also scavenged hydroxyl radicals. Thiopental scavenged all types of free radicals, including NO, whereas propofol did not scavenge superoxide radicals. In this retrospective analysis, we observed changes in oxidative antioxidant markers following the administration of thiopental in patients with severe head trauma. We identified the direct radical-scavenging activity of various sedatives used in clinical settings. Furthermore, we reported a representative case of traumatic brain injury wherein thiopental administration dramatically affected oxidative-stress-related biomarkers. This study suggests that, in the future, sedatives containing thiopental may be redeveloped as an antioxidant therapy through further clinical research.

Antioxidant layer enables chemically stable cathode-electrolyte interface towards durable and safe Li-ion batteries

Although nickel-rich layered lithium transition metal oxides are one of the most promising candidates for high energy-density Li-ion batteries in electric vehicle applications, they yet suffer from irreversible capacity fading and poor safety properties due to the unstable cathode-electrolyte interphase (CEI), especially at high voltage and high temperature. This instability is mainly caused by the attack of free radicals generated from electrolyte decomposition and active oxygen species (especially singlet oxygen) released from the surface lattice. Here, we propose a novel modification method to construct a protective antioxidant layer on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM). By scavenging free radicals and singlet oxygen, the antioxidant layer greatly reduces the interfacial side reactions and significantly suppresses irreversible rock-salt phase transitions and the associated oxygen species release, leading to the stabilization of the interface. As a result, superior electrochemical performance and enhanced thermal stabilities are achieved. Specifically, the modified NCM exhibits a capacity retention of 92.0% over 1000 cycles in full cells and a dramatic increase of onset temperature (T1) from 75.2 °C to 114.2 °C. This antioxidant layer modification by scavenging free radicals and singlet oxygen provides a new strategy for addressing challenges of CEI design, which is theoretically applicable to all layered transition metal oxide cathode materials.

Functional specialization of expanded orange carotenoid protein paralogs in subaerial Nostoc species.

Orange carotenoid protein (OCP) is a photoactive protein that participates in the photoprotection of cyanobacteria. There are 2 full-length OCP proteins, 4 N-terminal paralogs (helical carotenoid protein [HCP]), and 1 C-terminal domain-like carotenoid protein (CCP) found in Nostoc flagelliforme, a desert cyanobacterium. All HCPs (HCP1 to 3 and HCP6) from N. flagelliforme demonstrated their excellent singlet oxygen quenching activities, in which HCP2 was the strongest singlet oxygen quencher compared with others. Two OCPs, OCPx1 and OCPx2, were not involved in singlet oxygen scavenging; instead, they functioned as phycobilisome fluorescence quenchers. The fast-acting OCPx1 showed more effective photoactivation and stronger phycobilisome fluorescence quenching compared with OCPx2, which behaved differently from all reported OCP paralogs. The resolved crystal structure and mutant analysis revealed that Trp111 and Met125 play essential roles in OCPx2, which is dominant and long acting. The resolved crystal structure of OCPx2 is maintained in a monomer state and showed more flexible regulation in energy quenching activities compared with the packed oligomer of OCPx1. The recombinant apo-CCP obtained the carotenoid pigment from holo-HCPs and holo-OCPx1 of N. flagelliforme. No such carotenoid transferring processes were observed between apo-CCP and holo-OCPx2. The close phylogenetic relationship of OCP paralogs from subaerial Nostoc species indicates an adaptive evolution toward development of photoprotection: protecting cellular metabolism against singlet oxygen damage using HCPs and against excess energy captured by active phycobilisomes using 2 different working modes of OCPx.

Lycopene – the impact of supplementation on the skin aging process

The skin aging process is affected by multiple different factors (including sun exposure, smoking, poor diet) and reactive oxygen species (ROS). Under their influence, the skin becomes weaker, mainly elastin and collagen fibers are damaged. The amount of lipids is also reduced, leading to the death of the skin cells. The presence of free radicals also blocks the natural ability of the epidermis to regenerate. Each of these factors determines the acceleration of the signs of aging. To some extent, our body is able to deal with the free radicals by producing antioxidants. Regular supplementation is also a beneficial solution. Lycopene is a red pigment naturally found in tomatoes and is a known antioxidant. Among the carotenoids, it is the strongest singlet oxygen quencher and scavenger of peroxygen radicals, making it an important defense mechanism in the human body. The aim of this paper is to present the biological properties of lycopene in relation to its beneficial effect on the aging process of the skin.

Development of NLC- based Sunscreen Gel of Lutein and its in-vitro and ex-vivo Characterisation

Background: In humans, Carotenoids are important in scavenging singlet oxygen and peroxyl radicals. Lutein has been demonstrated in multiple studies to help protect the skin from photodamage, as well as provide a variety of other health advantages. In the recent decade, the topi-cal use of Lutein as a new ultraviolet (UV) protectant, anti-stress, and blue light filter capable of protecting skin from photodamage has piqued cosmetic and pharmacological attention. Because Lutein is insoluble, it was integrated into nanocarriers for topical administration. Objective: The objective of this study was to formulate an NLC-based sunscreen gel of Lutein. Method: Nanostructured lipid carriers (NLC) were prepared by melt emulsion ultrafiltration tech-nique and were evaluated for particle size, zeta potential, polydispersity index (PDI), drug loading (DL), encapsulation efficacy (EE), and in vitro drug release. The optimised formula was incorpo-rated into a gel base and an in-vitro sun protection factor (SPF) was determined. Ex- vivo permea-tion study was performed on rat skin using a Franz diffusion cell. Cocoa butter and rose oil were chosen as solid and liquid lipids for NLC formulation. Results: The particle size, PDI, zeta potential, entrapment efficiency, and in vitro drug release of optimised formulation (NLC5) were found to be 81.64 nm, 0.463, -14.1mV, 79.90 %, and 89.86% respectively. The SPF value of the Lutein-NLC-loaded gel was found to be 27.524. The drug flux Jss from NLC gel was measured in the range of 0.07955 g/cm2/h. Conclusion: The investigation suggested lipid nanoparticles as a suitable carrier for Lutein to be delivered as sunscreen gel.

Significance of Singlet Oxygen Molecule in Pathologies.

Reactive oxygen species, including singlet oxygen, play an important role in the onset and progression of disease, as well as in aging. Singlet oxygen can be formed non-enzymatically by chemical, photochemical, and electron transfer reactions, or as a byproduct of endogenous enzymatic reactions in phagocytosis during inflammation. The imbalance of antioxidant enzymes and antioxidant networks with the generation of singlet oxygen increases oxidative stress, resulting in the undesirable oxidation and modification of biomolecules, such as proteins, DNA, and lipids. This review describes the molecular mechanisms of singlet oxygen production in vivo and methods for the evaluation of damage induced by singlet oxygen. The involvement of singlet oxygen in the pathogenesis of skin and eye diseases is also discussed from the biomolecular perspective. We also present our findings on lipid oxidation products derived from singlet oxygen-mediated oxidation in glaucoma, early diabetes patients, and a mouse model of bronchial asthma. Even in these diseases, oxidation products due to singlet oxygen have not been measured clinically. This review discusses their potential as biomarkers for diagnosis. Recent developments in singlet oxygen scavengers such as carotenoids, which can be utilized to prevent the onset and progression of disease, are also described.

Study of cell protective effects of alcohols against UV-C radiation and comparison to gamma radiation

A singlet oxygen production was monitored using a singlet oxygen sensor green chemical probe; reaction of chemical probe with singlet oxygen produces a fluorescent endoperoxide. Adding ethanol to the irradiated system resulted in decrease of the fluorescence signal, which indicates a decrease in concentration of singlet oxygen formed under UV-C irradiation. Thus, ethanol was likely to quench singlet oxygen in a system under study. This quenching did not occur with the use of methanol. When irradiating E. coli cells in the presence of ethanol and Rose Bengal for higher singlet oxygen production, there was a greater reduction in the radiation sensitivity of the cells compared to the system without Rose Bengal. Higher concentration of ethanol caused greater protection of cells; thus, it is likely that ethanol can scavenge singlet oxygen and provide a partial protection of bacteria from the effects of UV-C radiation. These results were compared with previously published data where the bacteria were irradiated by gamma radiation in presence of alcohols.

Identification of bioactive constituents of chloroform fraction from Annona muricata leaf, its antioxidant activity and inhibitory potential against carbohydrate-hydrolyzing α-amylase and α-glucosidase activities linked to type II diabetes mellitus: In vitro study

Introduction: Secondary metabolites from plants have been found to play an important role in the treatment of diabetes mellitus (DM) and its complications. Therefore, the purpose of this study was to identify the chemical components of Annona muricata leaf chloroform fraction (CFAm) and its in vitro antioxidant properties, as well as inhibitory activity against α-amylase and α-glucosidase enzymatic activities. Methods: Gas chromatography–mass spectrometry (GC-MS) technique was engaged in the identification of phytochemical constituents. Antioxidant activities such as DPPH free radical scavenging ability, reducing power capacity, hydroxyl radical scavenging ability, singlet oxygen scavenging capacity, as well as α-amylase and α-glucosidase inhibition were carried out using standard in vitro methods. Results: GC-MS analysis of CFAm revealed the presence of 23 phytochemicals, out of which 5 compounds had the highest % compositions (i.e., octadecanoic acid (20.35%), 2-propanone, 1-(4-hydroxy-3-methoxyphenyl) (12.04%), isocomene (22.60%), 9, 12, 15 octadecatrienoic acid, methyl ester (Z,Z,Z) (28. 98%), and quercetin, 5TMS derivative (18.28%)). Also, CFAm demonstrated a significant (P<0.05) inhibition against DPPH (IC50= 26.33±1.39 mg/mL), with OH free radical scavenging capacity (65.46 ± 1.39 mg/100 g), singlet oxygen scavenging capacity (55.24 ± 1.22 mg/100 g), and showed ferric reducing power (84.52 ± 2.84 mg/100 g). Also, CFAm exhibited a significant (P<0.05) inhibition against α-glucosidase (IC50= 71.06 ±1.45 mg/ mL) and α-amylase (IC50= 73.88±1.58 mg/mL) in a concentration-dependent manners. Conclusion: The remarkable properties demonstrated by CFAm, which are essential for the management of DM, could probably be credited to the presence of the various identified phytonutrients.

Cover Feature: Spiro‐OMeTAD as Redox Mediator and Singlet Oxygen Scavenger in Lithium‐Oxygen Batteries (Batteries & Supercaps 12/2022)

Cover Feature: <i>Spiro‐</i>OMeTAD as Redox Mediator and Singlet Oxygen Scavenger in Lithium‐Oxygen Batteries (Batteries &amp; Supercaps 12/2022)