Photo- and Free Radical-Mediated Oxidation of Lipid Components During the Senescence of Phototrophic Organisms

Rontani, Jean‐François

doi:10.5772/34002

Cited by 27 publications

(41 citation statements)

References 110 publications

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“…Abiotic degradation can be an important process for the fate of phytodetritus (for reviews see [1,2]), although it has been less widely studied compared to its biologicallymediated (heterotrophic) counterpart. Abiotic degradation processes generally fall into two categories, photooxidation and autoxidation (free radical degradation).…”

Section: Introductionmentioning

confidence: 99%

“…These processes mainly involve singlet oxygen (type II photoprocesses), which reacts with most of the unsaturated lipid components of these organisms to produce allylic hydroperoxides. These compounds can then undergo: (1) highly specific allylic rearrangement [4], (2) heterolytic cleavage catalyzed by protons [5] leading to the formation of x-oxocarboxylic acids and other volatile products and (3) homolytic cleavage induced by transition metal ions [6,7] or UVR (since hydroperoxides absorb in the UVR range) [8]. Homolytic cleavage of hydroperoxyacids leads to the formation of alkoxyl radicals, which can then: (1) abstract a hydrogen atom from another molecule to give hydroxy acids, (2) lose a hydrogen atom to yield keto acids, or (3) undergo bcleavage reactions affording volatile products.…”

Section: Introductionmentioning

confidence: 99%

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Autoxidative and Photooxidative Reactivity of Highly Branched Isoprenoid (HBI) Alkenes

Rontani

Belt

Vaultier

et al. 2014

Lipids

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Autoxidation of several mono-, di-, tri- and tetra-unsaturated highly branched isoprenoid (HBI) alkenes was induced in organic solvents using a radical initiator and enhancer, and their degradation rates were compared to those of classical phytoplanktonic lipids (mono-unsaturated fatty acids, sterols and chlorophyll phytyl side-chain). Autoxidation of two HBI trienes was also investigated in senescent and highly photodegraded diatom cells, collected in the Antarctic, using Fe(2+) ions as radical inducers. Autoxidation rates of HBI alkenes were found to increase with the number of tri-substituted double bonds, as expected. Further, HBI trienes possessing one bis-allylic position (where hydrogen abstraction is highly favoured) were found to be particularly reactive towards autoxidation and degraded at similar rates compared to polyunsaturated fatty acids in diatom cells. By comparison of the autoxidation products of the most reactive tri-unsaturated HBI with the corresponding photooxidation products, some specific tracers of these two types of abiotic degradation processes were identified. The lack of reactivity of the mono-unsaturated HBI IP25 and a structurally similar di-unsaturated HBI towards autoxidative degradation supports the good preservation of these biomarkers in marine sediments.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Autoxidative and Photooxidative Reactivity of Highly Branched Isoprenoid (HBI) Alkenes

Rontani

Belt

Vaultier

et al. 2014

Lipids

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“…Moreover, note that the lifetime of 1 O 2 produced from sensitizers in a lipid-rich hydrophobic environment, such as a cellular medium, could be longer, and its potential diffusive distance is greater, than in an aqueous solution [18]. Therefore, it is not surprising that photodegradation processes act on the majority of unsaturated lipid components of senescent phytoplankton, including sterols, unsaturated fatty acids, chlorophyll phytyl side chain, carotenoids, and alkenes (for reviews, see [11,19]).…”

Section: Introductionmentioning

confidence: 99%

Photochemical Production and Behavior of Hydroperoxyacids in Heterotrophic Bacteria Attached to Senescent Phytoplanktonic Cells

Petit

Sempéré

Vaultier

et al. 2013

IJMS

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The photooxidation of cellular monounsaturated fatty acids was investigated in senescent phytoplanktonic cells (Emiliania huxleyi) and in their attached bacteria under laboratory controlled conditions. Our results indicated that UV-visible irradiation of phytodetritus induced the photooxidation of oleic (produced by phytoplankton and bacteria) and cis-vaccenic (specifically produced by bacteria) acids. These experiments confirmed the involvement of a substantial singlet oxygen transfer from senescent phytoplanktonic cells to attached bacteria, and revealed a significant correlation between the concentration of chlorophyll, a photosensitizer, in the phytodetritus and the photodegradation state of bacteria. Hydroperoxyacids (fatty acid photoproducts) appeared to be quickly degraded to ketoacids and hydroxyacids in bacteria and in phytoplanktonic cells. This degradation involves homolytic cleavage (most likely induced by UV and/or transition metal ions) and peroxygenase activity (yielding epoxy acids).

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“…The triplet state is much longer lived than the singlet state, which is the initial product issued from light absorption. Indirect photo-oxidation (photo-sensitized oxidation) can be intense during the senescence of phototrophic organisms (Rontani, 2012) due to the presence of chlorophyll, which is a very efficient photosensitizer (Foote, 1976) capable of generating singlet oxygen particularly reactive towards unsaturated cellular components (Type II photoprocesses). Chlorophyll may be also directly photodegraded by solar light (Nelson, 1993).…”

Section: Chlorophyllmentioning

confidence: 99%

Seasonal survey of the composition and degradation state of particulate organic matter in the Rhône River using lipid tracers

et al. 2015

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Abstract. Lipid tracers including fatty acids, hydroxyacids, n-alkanols, sterols and triterpenoids were used to determine the origin and fate of suspended particulate organic matter (POM) collected in the Rhône River (France). This seasonal survey (April 2011 to May 2013) revealed a yearround strong terrestrial higher-plant contribution to the particulate organic matter (POM), with significant algal inputs observed in March and attributed to phytoplanktonic blooms likely dominated by diatoms. Major terrigenous contributors to our samples are gymnosperms, and more precisely their roots and stems, as evidenced by the presence of high proportions of ω-hydroxydocosanoic acid (a suberin biomarker). The high amounts of coprostanol detected clearly show that the Rhône River is significantly affected by sewage waters.Specific sterol degradation products were quantified and used to assess the part of biotic and abiotic degradation of POM within the river. Higher-plant-derived organic matter appears to be mainly affected by photo-oxidation and autoxidation (free radical oxidation), while organic matter of mammal or human origin, evidenced by the presence of coprostanol, is clearly more prone to bacterial degradation. Despite the involvement of an intense autoxidation-inducing homolytic cleavage of peroxy bonds, a significant proportion of hydroperoxides is still intact in higher plant debris. These compounds could affect the degradation of terrestrial material by inducing an intense autoxidation upon its arrival at sea.

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Photo- and Free Radical-Mediated Oxidation of Lipid Components During the Senescence of Phototrophic Organisms

Cited by 27 publications

References 110 publications

Autoxidative and Photooxidative Reactivity of Highly Branched Isoprenoid (HBI) Alkenes

Autoxidative and Photooxidative Reactivity of Highly Branched Isoprenoid (HBI) Alkenes

Photochemical Production and Behavior of Hydroperoxyacids in Heterotrophic Bacteria Attached to Senescent Phytoplanktonic Cells

Seasonal survey of the composition and degradation state of particulate organic matter in the Rhône River using lipid tracers

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