Photooxidation Of Fatty Acids Research Articles

Enhanced Photochemical Volatile Organic Compounds Release from Fatty Acids by Surface-Enriched Fe(III).

Both Fe(III) and fatty acids are ubiquitous and important species in environmental waters. Because they are amphipathic, many fatty acids are surface active and prone to enrichment at the air-water interface. Here, we report that by using nonanoic acid (NA) as a model fatty acid, coexisting Fe(III), even at concentrations as low as 1 μM, markedly enhanced the photochemical release of NA-derived volatile organic compounds (VOCs) such as octanal and octane into the air. Further studies indicated that the surface-enriched fatty acids dramatically increase the local concentration of Fe(III) at the water surface, which enables Fe(III)-mediated photochemical reactions to take place at the air-water interface, and the VOCs facilely produced by fatty acid photooxidation can then be released into the air. Moreover, the product distribution in the Fe(III)-mediated reactions was largely different from that in other photochemical systems, and a mechanism based on photochemical decarboxylation is proposed. Considering that the coexistence of fatty acids and Fe(III) in the environment is common, the enhanced photochemical release of VOCs by surface-enriched fatty acids and Fe(III) may be an important channel for the atmospheric emission of VOCs, which are known to play an essential role in the formation of ozone and secondary organic aerosols.

Evaluation of Singlet Oxygen Scavenging Capacity of Peppermint (Mentha Piperita L.), Marjoram (Origanum Majorana L.), Rosemary (Rosmarinus Officinalis L.) And Sage (Salvia Officinalis L.) on Fatty Acid Photooxidation

Lipid photooxidation is the undesirable chemical process in which singlet oxygen result in the peroxidation of fatty acids. In this study leaves methanolic extracts of peppermint (Mentha piperita L.), marjoram (Origanum majorana L.), rosemary (Rosmarinus officinalis L.) and sage (Salvia officinalis L.) were applied as the natural singlet oxygen scavenger. Amount of flavonoid compounds as the singlet oxygen scavenger agent in these plant species were decreased in the order of peppermint > marjoram> sage > rosemary. Also, The rate of quenching of singlet oxygen in the presence of 1,4-Diazabicyclo[2.2.2]octane (DABCO) as a well-known singlet oxygen scavenger and highly effective synthetic antioxidants in food industry such as Butylated hydroxyanisole (BHA), tert-Butylhydroquinone (TBHQ) and peppermint decreased in the order of peppermint > BHA > TBHQ > DABCO >. Furthermore, photooxidation of oleic acid as an unsaturated fatty acid in the presence of DABCO, peppermint, BHA and TBHQ indicated a preservation of 82.77%, 73.39%, 71.57% and 53.10% on peroxidation of oleic acid, respectively which reveals peppermint has an efficient role on protection of fatty acids from photooxidation. Practical application: In this study, it was confirmed that peppermint (Mentha piperita L.) performs an effective role in restricting or limitation of singlet oxygen generation and fatty acid photooxidation. In vitro study of scavenging effect of peppermint can correlate laboratory results to commercial scale up. However, this would also necessitate the progress of improved methods for the measurement of lipid peroxidation in vivo in the presence of peppermint.

Suppressing Effect of 2-Nitrobenzaldehyde on Singlet Oxygen Generation, Fatty Acid Photooxidation, and Dye-Sensitizer Degradation.

2-Nitrobenzaldehyde was found to efficiently block singlet oxygen generation in a series of different test samples upon exposure to UV and visible light under aerobic conditions. The effect of quenching singlet oxygen formation was monitored in the presence of 1, 4-diazabicyclo [2.2.2] octane (DABCO) acting as a well-known singlet oxygen scavenger. A comparison of different nitrobenzaldehyde isomers with other highly effective synthetic antioxidants used in the food industry such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ) revealed that the protection of materials from singlet oxygen decreases in the order of 2-nitrobenzaldehyde > DABCO > TBHQ > 3-nitrobenzaldehyde > BHA > 4-nitrobenzaldehyde > BHT. Upon addition of 2-nitrobenzaldehyde, the oxidation of fatty acids and the degradation of photosensitizers was found to be considerably diminished, which indicates that the presence of 2-nitrobenzaldehyde has a significant protective influence by restricting the singlet oxygen generation and photodegradation of dyes. Moreover, the compound turned out to display its highly suppressing effects on typical singlet oxygen-dependent reactions, such as fatty acid photooxidation and dye photosensitizer degradation, in a rather broad spectral region covering wavelengths from 300 nm (UV-B) to 575 nm (close to the maximum of ambient solar radiation).

Use of palmitoleic acid and its oxidation products for monitoring the degradation of ice algae in Arctic waters and bottom sediments

Degradation of palmitoleic acid (C16:1ω7), the main fatty acid component of sea ice-associated (sympagic) diatoms, was monitored in Arctic sea ice at the beginning of ice melting and in the underlying sinking particles and superficial bottom sediments. In sea ice, degradation of sympagic algae involved biotic oxidation induced by 10S-DOX-like lipoxygenase of unknown salinity-stressed attached bacteria, while photo- and autoxidation were limited. In the water column, strong hydratase and Z/E isomerase activity were observed. Hydration of unsaturated fatty acids seems to be a detoxification strategy, which is essential for bacterial survival when associated with free fatty acid-rich environments such as ice algae. In contrast, Z/E isomerisation of palmitoleic acid was attributed to the release of Fe2+ ions during radical-induced damage of the active site of the bacterial 10S-DOX-like lipoxygenase and Z/E isomerases. Due to the poor physiological state of their attached bacteria resulting from salinity stress in brine channels or toxicity of free ice algae fatty acids, sympagic algae appeared to be only very weakly biotically degraded within the water column. In bottom sediments, free radicals resulting from 10S-DOX-like lipoxygenase activity induced a strong autoxidation of the ice algal material. The presence in bottom sediments of a significant proportion of oxidation products resulting from 10S-DOX-like lipoxygenase activity attested to the strong contribution of sea ice-derived OM released during the early stages of ice melt prior to deposition in the sediments. However, on the basis of the highest fatty acid photooxidation state observed in these sediments, an additional contribution of highly photooxidized material (ice algal material released at the end of ice melting or open water phytoplankton) seems likely. The degradation of hydroperoxides, resulting from biotic and abiotic degradation of palmitoleic acid, appeared to involve: (i) homolytic cleavage of the peroxyl group affording the corresponding hydroxy- and oxoacids, (ii) reduction to the corresponding hydroxyacids by peroxygenases, (iii) heterolytic proton-catalysed cleavage and (iv) conversion to allylic 1,4-diols by diol synthases and hydroperoxide isomerases.

Factors Related to the Light Stability of Vitamin A in Various Carriers

Skim milk fortified with all-trans retinyl palmitate, using corn or coconut oil as the vitamin carrier, was studied to determine the effect of physical state and droplet size of the carrier system on loss of all-trans retinyl palmitate during exposure to light. To determine effect of physical state, fortified samples were exposed to light at 4°C, where corn oil is liquid and coconut oil solid, or 35°C where both oils are liquid. At 4°C, rates of light degradation of all-trans retinyl palmitate in corn or coconut oil were significantly different from each other; at 35°C they were not. Different droplet sizes of the carrier systems were achieved by homogenizing skim milk at different pressures (169, 105, or 35 kg/cm2). In all cases, greater loss occurred in corn oil as the vitamin carrier compared to coconut oil. Degradation rate of all-trans retinyl palmitate increased with decreased homogenization pressure.Effects of photooxidation of fatty acids on degradation of all-trans retinyl palmitate and isomerization of retinyl palmitate were investigated in four carrier systems (corn, butter, peanut, and coconut) by exposing the fortified oils to light. Peroxide values did not parallel degradation of all-trans retinyl palmitate during light exposure. Isomerization of all-trans to cis isomers of retinyl palmitate occurred in all carrier systems.

Tert-butylated-hydroxytoluene-sensitized photo-oxidation of fatty acids: Inhibition by 1,4-diazabicyclo-[2.2.2] octane and role of singlet oxygen

The effect of tert-butylated hydroxytoluene (BHT) on the photo-oxidation of fatty acids was studied. A marked increase in photo-oxidation was observed in the presence of BHT. The major products of photo-oxidation were identified as epoxides of the fatty acids and only a small amount of hydroperoxides was detected. Formation of epoxides as the major product indicates that enhancement in the photo-oxidation occurs through free radicals, possibly through a type I mechanism. Analyses of the hydroperoxides, however, showed the formation of both conjugated and non-conjugated hydroperoxides, suggesting the involvement of a type II mechanism also in the photo-oxidation. Formation of both free radicals and singlet oxygen products was inhibited by 1,4-diazabicyclo [2.2.2] octane, a widely used singlet oxygen quencher, suggesting that hydroperoxides may be the primary products of photo-oxidation followed by free-radical reactions leading to the formation of the epoxy compounds.

Effect of antioxidants on the photooxidation of fatty acids.

The effect of butylated hydroxytoluene (BHT), butylated hydroxy anisole (BHA) and tocopherol acetate on photooxidation of the fatty acids was studied. A marked increase in the photooxidation was observed in the presence of BHT, and this effect was further potentiated by hexabromobiphenyls. Conversely, BHA and tocopherol acetate as such did not show any significant effect, but greatly enhanced the photooxidation when hexabromobiphenyls were also present. Hexabromobiphenyls by themselves did not show any notable effect on the photooxidation.

PHOTO-OXIDATION OF UNSATURATED LIPIDS IN CUCUMIS LEAF DISCS DURING CHILLING

SUMMARY Unsaturated lipids in Cucumis leaf discs at 1°C undergo a photo-oxidative degradation which can be measured with the thiobarbituric-acid test. Kinetics of thiobarbituric-acid-reactivity (TBAR) show a lag phase followed by a rapidly increasing phase and a final decreasing phase. DCMU inhibits the photo-oxidative increase of TBAR. Among all combined fatty acids of Cucumis leaf discs linolenic acid is the most abundant (72.6%). The fatty acid composition of Cucumis leaf discs shows little alteration after 8 hours light at 1 °C but after 24 and 48 hours light there is a fast degradation of linolenic acid as compared to the rest of the fatty acids. A crude action spectrum shows a high maximum of TBAR in the blue and a lower maximum in the red spectral region and minimal TBAR in the green and in the far red region. It is suggested that chlorophyll and carotenoids are sensitizers of unsaturated fatty acid photo-oxidation. Possible connexions between chlorophyll and photo-oxidative fatty acid degradation are discussed.