Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters

This article is a review of the fundamental chemistry of the tocopherols and tocotrienols relevant to their antioxidant action. Despite the general agreement that α-tocopherol is the most efficient antioxidant and vitamin E homologuein vivo, there was always a considerable discrepancy in its “absolute” and “relative” antioxidant effectivenessin vitro, especially when compared to γ-tocopherol. Many chemical, physical, biochemical, physicochemical, and other factors seem responsible for the observed discrepancy between the relative antioxidant potencies of the tocopherolsin vivo andin vitro. This paper aims at highlighting some possible reasons for the observed differences between the tocopherols (α-, β-, γ-, and δ-) in relation to their interactions with the important chemical species involved in lipid peroxidation, specifically trace metal ions, singlet oxygen, nitrogen oxides, and antioxidant synergists. Although literature reports related to the chemistry of the tocotrienols are quite meager, they also were included in the discussion in virtue of their structural and functional resemblance to the tocopherols.

The chemistry and antioxidant properties of tocopherols and tocotrienols

Aspirin (ASA) is unique among current therapies because it acetylates cyclooxygenase (COX)-2 enabling the biosynthesis of R- containing precursors of endogenous antiinflammatory mediators. Here, we report that lipidomic analysis of exudates obtained in the resolution phase from mice treated with ASA and docosahexaenoic acid (DHA) (C22:6) produce a novel family of bioactive 17 R -hydroxy-containing di- and tri-hydroxy-docosanoids termed resolvins. Murine brain treated with aspirin produced endogenous 17 R -hydroxydocosahexaenoic acid as did human microglial cells. Human COX-2 converted DHA to 13-hydroxy-DHA that switched with ASA to 17 R -HDHA that also proved a major route in hypoxic endothelial cells. Human neutrophils transformed COX-2-ASA‐derived 17 R -hydroxy-DHA into two sets of novel diand trihydroxy products; one initiated via oxygenation at carbon 7 and the other at carbon 4. These compounds inhibited (IC 50 � 50 pM) microglial cell cytokine expression and in vivo dermal inflammation and peritonitis at ng doses, reducing 40‐80% leukocytic exudates. These results indicate that exudates, vascular, leukocytes and neural cells treated with aspirin convert DHA to novel 17 R -hydroxy series of docosanoids that are potent regulators. These biosynthetic pathways utilize omega-3 DHA and EPA during multicellular events in resolution to produce a family of protective compounds, i.e., resolvins, that enhance proresolution status.

https://rupress.org/jem/article-pdf/196/8/1025/1142248/jem19681025.pdf

Resolvins: a family of bioactive products of omega-3 fatty acid transformation circuits initiated by aspirin treatment that counter proinflammation signals.

ion step follows the decarboxylation, which is consistent with the deuterium isotopic effects observed for thymine 7-hydroxylase which indicate that an irreversible step (or steps) occurs prior to the C-H bond breaking.395 It has also been shown for prolyl 4-hydroxylase that a substrate-derived radical is generated in the reaction, which is consistent with a rebound mechanism.437 It is important to point out that no oxygen intermediate (i.e., bridged superoxo or oxo-ferryl) has been observed for any R-KGdependent enzyme. This warrants future theoretical and experimental study. A detailed molecular mechanism has been proposed for IPNS based on spectroscopic and crystallographic studies.422 Resting IPNS/FeII is also 6C and thus relatively stable toward dioxygen. Substrate ACV binds directly to FeII IPNS through its thiolate group, providing an open coordination position at the FeII. O2 can then react to form an FeIII-superoxo intermediate. This intermediate is suggested422 to perform the first hydrogen-atom abstraction step and close the â-lactam ring, resulting in the formation of the first water molecule and generating an FeIVdO-II intermediate, which completes the second ringclosure process by hydrogen-atom abstraction forming a thiazolidine ring. Previously proposed mechanisms of ACCO involved direct binding of cosubstrate ascorbate to the iron before O2 as part of the oxygen activation process.438,439 The EPR and ESEEM studies of the NO complex of ACCO suggested a quite different molecular mechanism for ACCO.435 An FeIII-superoxo intermediate is proposed. Whether it is preceded by a 6C f 5C process with substrate binding is presently under study.440 This intermediate is thought to initiate a radical process by single hydrogen-atom abstraction or electron-coupled proton transfer (PT)ion or electron-coupled proton transfer (PT) from the bound amino group. The resulting substrate radical may undergo spontaneous conversion into products. The role of cosubstrate ascorbate is proposed to reduce the toxic peroxo byproduct to water. Alternatively, the two-electron reduction of FeIIIsuperoxo by the cosubstrate ascorbate could result in an FeIVdO-II intermediate which initiates the radical reaction.435 4. Rieske-Type Dioxygenases Biochemical Characterization. The Rieske ironsulfur center is a two iron-two sulfur cluster ([2Fe2S]) which has a 2His (on one iron), 2Cys (on the other iron) coordination environment, instead of the 4Cys present in plant ferredoxins. It plays a key role in the electron transport pathway in membranebound cytochrome complexes as well as in some dioxygenases.441 The latter are mainly comprised of two protein components: a reductase containing flavin and a ferredoxin [2Fe-2S], and a terminal oxygenase containing a Rieske [2Fe-2S] cluster and a non-heme iron active site.442 Except for the recently reported alkene monooxygenase that has a binuclear iron site in its terminal oxygenase,10 most of the Rieske-type oxygenases have a mononuclear iron site, which is believed to be the site of dioxygen activation and substrate oxygenation.442,443 The majority of the Rieske-type mononuclear non-heme oxygenases form a family of enzymes which are aromatic-ring-hydroxylating dioxygenases. These catalyze the regioand stereospecific cis-dihydroxylation of an aromatic ring using dioxygen and NAD(P)H (Table 1). Examples include benzene dioxygenase (BDO, EC 1.14.12.3),444 phthalate dioxygenase (PDO, EC 1.14.12.7),445 toluene dioxygenase (EC 1.14.12.11),446 and naphthalene 1,2-dioxygenase (NDO, EC 1.14.12.12),447 which initiate the aerobic degradation of aromatic compounds in the soil bacteria and are targets for bioengineering in bioremediation. This step is the first step in the pathway that ultimately leads to ring cleavage by the intraand extradiol dioxygenases (sections II.B.2 and II.C.1).443 Besides these bacterial dioxygenases, other Rieske-type mononuclear non-heme oxygenases include anthranilate 1,2-dioxygenase (EC 1.14.12.1),448 which deaminates and decarboxylates the substrate to produce catechol; chlorophenylacetate 3,4-dioxygenase (EC 1.14.2.13),449 which converts substrate to catechol with chloride elimination; and 4-methoxybenzoate O-demethylase (putidamonooxin),450 which catalyzes the conversion of 4-methoxybenzoic acid to 4-hydroxybenzoic acid and formaldehyde. The reductase component is usually a monomer (MW ) 12-15 kDa) and utilizes flavin to mediate ET from the two-electron donor NAD(P)H to the oneelectron acceptor [2Fe-2S] cluster and is specific to each terminal oxygenase; other electron donors do not support efficient oxygenation.442 The crystal structure of phthalate dioxygenase reductase is available.451 The terminal oxygenases are large protein aggregates (MW ) 150-200 kDa) containing either multiples of R subunits (BDO R2, PDO R4) or an equimolar combination of R and â subunits (toluene dioxygenase R2â2, NDO R3â3). The R subunits contain a Rieske [2Fe-2S] cluster and a catalytic non-heme FeII center. â subunits do not seem to be involved in the catalytic function (vide infra). Kinetics. Steady-state kinetic studies coupled with various rapid reaction studies of the partial reactions of PDO allowed Ballou et al. to propose a kinetic scheme (Scheme 15).443 On the basis of steady state 278 Chemical Reviews, 2000, Vol. 100, No. 1 Solomon et al.

Geometric and Electronic Structure/Function Correlations in Non-Heme Iron Enzymes

Review on sustainable thermal energy storage technologies, Part I: heat storage materials and techniques

Fatty acid structure. Lipid structure. Occurrence and characteristics of oils and fats. Separation and isolation procedures. Processing of fats and oils. Analytical methods. Synthesis. Physical properties - structural and physical characteristics. Physical properties - optical and spectral characteristics. Chemical properties. Lipid metabolism. Medical and agricultural aspects of lipids. Dictionary section. Compound name index. Formula index.

The lipid handbook

Preface to the First Edition. Preface to the Second Edition. Contributors. List of Abbreviations. 1 Production and Trade of Vegetable Oils ( Frank D. Gunstone ). 1.1 Extraction, refining and processing. 1.2 Vegetable oils: Production, consumption and trade. 1.3 Some topical issues. 2 Palm Oil ( Siew Wai Lin ). 2.1 Introduction. 2.2 Composition and properties of palm oil and fractions. 2.3 Physical characteristics of palm oil products. 2.4 Minor components of palm oil products. 2.5 Food applications of palm oil products. 2.5.1 Cooking/frying oil. 2.6 Nutritional aspects of palm oil. 2.7 Sustainable palm oil. 2.8 Conclusions. 3 Soybean Oil ( Tong Wang ). 3.1 Introduction. 3.2 Composition of soybean and soybean oil. 3.3 Recovery and refining of soybean oil. 3.4 Oil composition modification by processing and biotechnology. 3.5 Physical properties of soybean oil. 3.6 Oxidation evaluation of soybean oil. 3.7 Nutritional properties of soybean oil. 3.8 Food uses of soybean oil. 4 Canola/Rapeseed Oil ( Roman Przybylski ). 4.1 Introduction. 4.2 Composition. 4.3 Physical and chemical properties. 4.4 Major food uses. 4.5 Conclusion and outlook. 5 Sunflower Oil ( Maria A. Grompone ). 5.1 Introduction. 5.2 Sunflower oil from different types of seed. 5.3 Physical and chemical properties. 5.4 Melting properties and thermal behaviour. 5.5 Extraction and processing of sunflower oil. 5.6 Modified properties of sunflower oil. 5.7 Oxidative stability of commercial sunflower oils. 5.8 Food uses of different sunflower oil types. 5.9 Frying use of commercial sunflower oil types. 6 The Lauric (Coconut and Palm Kernel) Oils ( Ibrahim Nuzul Amri ). 6.1 Introduction. 6.2 Coconut oil. 6.3 Palm kernel oil. 6.4 Processing. 6.5 Food uses. 6.6 Health aspects. 7 Cottonseed Oil ( Michael K. Dowd ). 7.1 Introduction. 7.2 History. 7.3 Seed composition. 7.4 Oil composition. 7.5 Chemical and physical properties of cottonseed oil. 7.6 Processing. 7.7 Cottonseed oil uses. 7.8 Co-product uses. 8 Groundnut (Peanut) Oil ( Lisa L. Dean, Jack P. Davis, and Timothy H. Sanders ). 8.1 Peanut production, history, and oil extraction. 8.2 Oil uses. 8.3 Composition of groundnut oil. 8.4 Chemical and physical characteristics of groundnut oil. 8.5 Health issues. 9 Olive Oil ( Dimitrios Boskou ). 9.1 Introduction. 9.2 Extraction of olive oil from olives. 9.3 Olive oil composition. 9.4 Effect of processing olives on the composition of virgin olive oils. 9.5 Refining and modification. 9.6 Hardening and interesterification. 9.7 Quality, genuineness and regulations. 9.8 Consumption and culinary applications. 10 Corn Oil ( Robert A. Moreau ). 10.1 Composition of corn oil. 10.2 Properties of corn oil. 10.3 Major food uses of corn oil. 10.4 Conclusions. 11 Minor and Speciality Oils ( S. Prakash Kochhar ). 11.1 Introduction. 11.2 Sesame seed oil. 11.3 Rice bran oil. 11.4 Flaxseed (linseed and linola) oil. 11.5 Safflower oil. 11.6 Argan kernel oil. 11.7 Avocado oil. 11.8 Camelina seed oil. 11.9 Grape seed oil. 11.10 Pumpkin seed oil. 11.11 Sea buckthorn oil. 11.12 Cocoa butter and CBE. 11.13 Oils containing a-linolenic acid (GLA) and stearidonic acid (SDA). 11.14 Tree nut oils. Useful Websites. Index.

http://health120years.com/cn/pdf/hd_Vegetable.Oils.pdf

Vegetable Oils in Food Technology: Composition, Properties, and Uses

Fatty Acids. Nomenclature, Structure, Isolation and Structure-Determination, Biosynthesis and Chemical Synthesis. Lipids: Nomenclature, Structure, Biosynthesis and Chemical Synthesis. The Major Sources of Oils, Fats and Other Lipids. Processing: Extraction, Refining, Fractionation, Hydrogenation, Interesterfication Analytical Procedures. Physical Properties. Reactions Associated with Double Bonds. Reactions of the Carboxyl Group. Dietary Fats and Nutrition. Practical Applications of Oils and Fats

Fatty acid and lipid chemistry

Occurrence and Characteristics of Oils and Fats

1. Oils and fats: sources and constituents. 2. Extraction, refining and processing. 3. Structure of fatty acids and lipids. 4. Chemical and biological synthesis of fatty acids and lipids. 5. Analytical procedures. 6. Physical properties. 7. Chemical properties related to unsaturated centres. 8. Chemical properties related to the carboxyl group. 9. Nutritional properties. 10. Edible uses of oils and fats. 11. Non--edible uses of oils and fats. ReferencesIndex

Frank D. Gunstone

Papers

The lipid handbook

Vegetable Oils in Food Technology: Composition, Properties, and Uses

Fatty acid and lipid chemistry

Occurrence and Characteristics of Oils and Fats

The Chemistry of Oils and Fats: Sources, Composition, Properties, and Uses