Quantification Of Hydroperoxides Research Articles

Antioxidant and Cytoprotective Properties of Polyphenol-Rich Extracts from Antirhea borbonica and Doratoxylon apetalum against Atherogenic Lipids in Human Endothelial Cells.

The endothelial integrity is the cornerstone of the atherogenic process. Low-density lipoprotein (LDL) oxidation occurring within atheromatous plaques leads to deleterious vascular effects including endothelial cell cytotoxicity. The aim of this study was to evaluate the vascular antioxidant and cytoprotective effects of polyphenol-rich extracts from two medicinal plants from the Reunion Island: Antirhea borbonica (A. borbonica), Doratoxylon apetalum (D. apetalum). The polyphenol-rich extracts were obtained after dissolving each dry plant powder in an aqueous acetonic solution. Quantification of polyphenol content was achieved by the Folin–Ciocalteu assay and total phenol content was expressed as g gallic acid equivalent/100 g plant powder (GAE). Human vascular endothelial cells were incubated with increasing concentrations of polyphenols (1–50 µM GAE) before stimulation with oxidized low-density lipoproteins (oxLDLs). LDL oxidation was assessed by quantification of hydroperoxides and thiobarbituric acid reactive substances (TBARS). Intracellular oxidative stress and antioxidant activity (catalase and superoxide dismutase) were measured after stimulation with oxLDLs. Cell viability and apoptosis were quantified using different assays (MTT, Annexin V staining, cytochrome C release, caspase 3 activation and TUNEL test). A. borbonica and D. apetalum displayed high levels of polyphenols and limited LDL oxidation as well as oxLDL-induced intracellular oxidative stress in endothelial cells. Polyphenol extracts of A. borbonica and D. apetalum exerted a protective effect against oxLDL-induced cell apoptosis in a dose-dependent manner (10, 25, and 50 µM GAE) similar to that observed for curcumin, used as positive control. All together, these results showed significant antioxidant and antiapoptotic properties for two plants of the Reunion Island pharmacopeia, A. borbonica and D. apetalum, suggesting their therapeutic potential to prevent cardiovascular diseases by limiting LDL oxidation and protecting the endothelium.

Quantification of Hydroperoxides by Gas Chromatography with Flame Ionisation Detection

Hydroperoxides are of great importance in the fields of atmospheric and biological chemistry. However, there are several analytical challenges in their analysis: unknown and usually low UV absorption coefficients, high reactivity, thermal instability, and a lack of available reference standards. To overcome these limitations, we propose a GC-FID approach involving pre-column silylation and quantification via the effective carbon number approach. Four hydroperoxides of α-pinene were synthesized in the liquid phase with singlet oxygen and identified using literature data on isomer yield distribution, MS spectra, estimated boiling temperatures of each isomer (retention time), their thermal stability and derivatisation rate. The developed procedure was used for the determination of hydroperoxides in bottled and autooxidised turpentine. We anticipate that this method could also be applied in atmospheric chemistry, where the reactivity of singlet oxygen could help explain the high formation rates of secondary organic aerosols.

Influence of Ternary Emulsifier Mixtures on Oxidative Stability of Nanoemulsions Based on Avocado Oil.

The aim of this work was to study the effect of two emulsifiers (M1: SL-soy lecithin, Tw80-Tween 80 and CasCa-calcium caseinate and M2: SL-soy lecithin, Tw80-Tween 80 and SE-sucrose esters) on the oxidative stability of avocado oil-based nanoemulsions. Oil-in-water nanoemulsions were prepared using 3.6% w/w of two emulsifier mixtures, which were optimized by mixture experimental design in order to minimize particle size (PS) and polydispersity index (PdI). Then, the oxidative stability of nanoemulsions was evaluated through both an induction period and a quantification of hydroperoxides and thiobarbituric acid reactive species (TBARs) under accelerated storage conditions. The simplex-centroid mixture design showed that PS and PdI varied when proportions of different emulsifiers were modified, obtaining an optimized concentration for each mixture of: 85% SL, 10% Tw80 and 5%CasCa (M1) and 85% SL, 7.4% Tw80 and 7.6% SE (M2) that produced nanoemulsions with PS ~116 nm and PdI < 0.2. Nanoemulsions elaborated with M1 and M2 presented similar particle characteristics and physical stability to the control sample with Tw80. However, M1 nanoemulsions were more stable against lipid oxidation, since they showed the highest induction period and lower formation of hydroperoxides and TBARs during storage.

Exposure source for skin sensitizing hydroperoxides of limonene and linalool remains elusive: An analytical market surveillance

Positive patch test reactions of dermatological patients to oxidized samples of linalool and limonene are frequently reported. The sensitizing ingredients in the oxidation mixtures are hydroperoxides (HP). It is not clear whether fragranced consumer products are a relevant exposure source for HP. Analytical methodologies had been validated, allowing quantification of HP in different consumer products. The analytical approach was used to analyse 104 consumer products. Samples included aged and new samples from the same brand, products suspected by patients to elicit their symptoms and products containing essential oils. Only four samples contained >50 μg/g of at least one of the HP by the screening method. Confirmatory analysis by LC-MS methods indicated that levels are even below those observed by the conservative screening method. The samples retrieved from patch-test positive patients were below detection limit for all target analytes. This market surveillance indicates that concentrations of HP in consumer products and patient products are orders of magnitude below sensitizing doses in animal tests. No evidence for hydroperoxide accumulation in aged products or products used by patients was found. The nature and source of the inducing agent responsible for the frequent positive patch test reactions to oxidized terpenes remains elusive.

Quantification of hydroperoxides by gas chromatography‐flame ionization detection and predicted response factors

AbstractThe quantification of hydroperoxides is crucial in several areas, in particular in the fragrance domain, because they have been identified as skin sensitizers. The reference compounds necessary to calibrate the instruments have very limited availability, and require drastic storage conditions (‐78 °C) due to their instability. To overcome these limitations, we propose a GC‐FID approach involving their silylation, and the prediction of response factors. This procedure provides a good alternative to a full calibration down to a concentration level of 500 mg/kg, with an underestimation of about 20%. In the analysis of essential oils and fragrance concentrates, larger deviations are found; however, they are not inherent in the technique but rather in the chemistry of hydroperoxides that readily react with aldehydes to form peroxyhemiacetals, thereby decreasing the concentration of free hydroperoxides. These observations are in agreement with quantitative 1H NMR and HPLC‐Chemiluminescence analyses. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Ozone Dosage Effect on C6 Cell Growth: in Vitro and in Vivo Tests.

C6 rat glioma cells are one of the most aggressive carcinogenic tumors, due to its high mortality rate in human beings and animals. The current treatment for this illness includes surgery, radio and chemotherapy, showing relapse in patients treated with those therapies. Since the ozone was found to be an effective bioreactive to inhibit growth of several carcinoma cells in vitro and in vivo. In this research, therapeutic peritoneum insufflation of ozone/oxygen dissolved in the physiological solution of NaCl 0.9% was dosed for fifteen days on different female mice groups in an advanced stage of C6 tumor (n=6). The first of them was the control group which had no treatment, the second group was dosage with oxygen every second day, the third group was dosed with ozone every second day, and finally the fourth group was dosed with ozone dissolved every fifth day. The size of the tumor was higher in both groups dosage by ozone, nevertheless tumor activity measured by microPET was 98% less in the fourth group compared with the control group. That result proves that ozone provokes an increase in the tumor volume even though the decrease of the cell activity. Those results were confirmed by the quantification of hydroperoxides, total cholesterol and total triglycerides.

Photosensitized oxidation of phosphatidylethanolamines monitored by electrospray tandem mass spectrometry

Photodynamic therapy combines visible light and a photosensitizer (PS) in the presence of molecular oxygen to generate reactive oxygen species able to modify biological structures such as phospholipids. Phosphatidylethanolamines (PEs), being major phospholipid constituents of mammalian cells and membranes of Gram-negative bacteria, are potential targets of photosensitization. In this work, the oxidative modifications induced by white light in combination with cationic porphyrins (Tri-Py(+)-Me-PF and Tetra-Py(+)-Me) were evaluated on PE standards. Electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) were used to identify and characterize the oxidative modifications induced in PEs (POPE: PE 16:0/18:1, PLPE: PE 16:0/18:2, PAPE: PE 16:0/20:4). Photo-oxidation products of POPE, PLPE and PAPE as hydroxy, hydroperoxy and keteno derivatives and products due to oxidation in ethanolamine polar head were identified. Hydroperoxy-PEs were found to be the major photo-oxidation products. Quantification of hydroperoxides (PE-OOH) allowed differentiating the potential effect in photodamage of the two porphyrins. The highest amounts of PE-OOH were notorious in the presence of Tri-Py(+)-Me-PF, a highly efficient PS against bacteria. The identification of these modifications in PEs is an important key point in the understanding cell damage processes underlying photodynamic therapy approaches.

Detection of chemiluminescence in lipid peroxidation of biological systems and its application to HPLC.

A combined system of chemiluminescence detection and high performance liquid chromatography (CL-HPLC) was developed to determine primary peroxidation products in biological tissues, such as phosphatidylcholine hydroperoxide (PCOOH). The CL-HPLC assay consists of separation of lipid classes with HPLC and detection of hydroperoxide-specific chemiluminescence. Hydroperoxides react with heme compounds to produce oxidants as suggested by our early studies on tissue low-level chemiluminescence in which singlet molecular oxygen is generated as one of the excited species in several biological systems involving free radical events. In the CL-HPLC method, a cytochrome c-luminol mixture was used as a hydroperoxide-specific luminescent reagent, and the quantification of hydroperoxide was performed by detecting chemiluminescence due to the luminol oxidation caused by the oxidant produced during the lipid hydroperoxides with heme. The detection limit of PCOOH was 10 pmole hydroperoxide-O2. PCOOH in normal human blood was found to be 10-500 pmol/ml plasma and significantly higher levels of PCOOH were observed in some hospitalized patients.