Inhibition kinetics of chain-breaking phenolic antioxidants in SDS micelles.  Evidence that intermicellar diffusion rates may be rate-limiting for hydrophobic inhibitors such as .alpha.-tocopherol

Castle, Laurence; Perkins, M. J.

doi:10.1021/ja00280a041

Cited by 143 publications

(88 citation statements)

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“…In this context, a mass transfer-based approach to account for lipid oxidation describes a school of thought implying that the oxidation rate can be primarily affected by the mass transport of reactants (i.e., free radicals, lipid substrates, LOOHs, and transition metals). By the same line of reasoning, such an approach has been theoretically developed to account for the antioxidant activity in multiphase systems (Laguerre et al 2013b) and has been experimentally demonstrated by Niki (1997), Ingold et al (1993), and Castle & Perkins (1986).…”

Section: The Neglected Role Of Dynamic Motion Of Reactantsmentioning

confidence: 97%

“…According to the authors, the phytyl chain enhances the retention of α-tocopherol in liposomes and hence suppresses the ability of α-tocopherol to transfer between liposomal membranes. One year later, Castle & Perkins (1986) pointed out the importance of the intermicellar diffusion rate in antioxidant capacity of hydrophobic antioxidants such as α-tocopherol in SDS micelles. In liposomal systems, Takahashi et al (1992) concluded that the intramembrane and intermembrane mobilities of ascorbic acid alkyl esters decreased with increasing number and length of fatty acid chains.…”

Section: Unlocking the Antioxidant Mass Transport Mechanism To Undersmentioning

confidence: 99%

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Mass Transport Phenomena in Lipid Oxidation and Antioxidation

Laguerre

Bily

Roller³

et al. 2017

Annu. Rev. Food Sci. Technol.

133

121

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In lipid dispersions, the ability of reactants to move from one lipid particle to another is an important, yet often ignored, determinant of lipid oxidation and its inhibition by antioxidants. This review describes three putative interparticle transfer mechanisms for oxidants and antioxidants: (a) diffusion, (b) collision-exchange-separation, and (c) micelle-assisted transfer. Mechanism a involves the diffusion of molecules from one particle to another through the intervening aqueous phase. Mechanism b involves the transfer of molecules from one particle to another when the particles collide with each other. Mechanism c involves the solubilization of molecules in micelles within the aqueous phase and then their transfer between particles. During lipid oxidation, the accumulation of surface-active lipid hydroperoxides (LOOHs) beyond their critical micelle concentration may shift their mass transport from the collision-exchange-separation pathway (slow transfer) to the micelle-assisted mechanism (fast transfer), which may account for the transition from the initiation to the propagation phase. Similarly, the cutoff effect governing antioxidant activity in lipid dispersions may be due to the fact that above a certain hydrophobicity, the transfer mechanism for antioxidants changes from diffusion to collision-exchange-separation. This hypothesis provides a simple model to rationalize the design and formulation of antioxidants and dispersed lipids.

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Section: The Neglected Role Of Dynamic Motion Of Reactantsmentioning

confidence: 97%

Section: Unlocking the Antioxidant Mass Transport Mechanism To Undersmentioning

confidence: 99%

Mass Transport Phenomena in Lipid Oxidation and Antioxidation

Laguerre

Bily

Roller³

et al. 2017

Annu. Rev. Food Sci. Technol.

133

121

View full text Add to dashboard Cite

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“…In a more polar medium k8 declines dramatically-e.g., k8 has a value of =5 x 105 M-1's-1 at 3TC in homogeneous alcoholic solutions (20), 4-6 x 104 M-1 s-1 at 3rC-400C in SDS micelles (37,38), and 3-6 x 103 M-1 s-1 in dilinoleoylphosphatidylcholine (DLPC) bilayers at 37°C (39,40). In both the SDS micelles and the DLPC bilayers, k3 also decreases but only to about half its value in a homogeneous lipid environment-to 30-40 M-1 s-1 at 30°C-37°C (39,40).…”

Section: General Background To These Problemsmentioning

confidence: 99%

Autoxidation of lipids and antioxidation by alpha-tocopherol and ubiquinol in homogeneous solution and in aqueous dispersions of lipids: unrecognized consequences of lipid particle size as exemplified by oxidation of human low density lipoprotein.

Ingold

Bowry

Stocker

et al. 1993

Proc. Natl. Acad. Sci. U.S.A.

314

168

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Contributed by Cheves Walling, August 5, 1992 ABSTRACT Recent studies on the initial stages in oxidation of low density lipoprotein (LDL) have revealed certain previously unrecognized similarities to emulsion polymerization and some quite unexpected features including the following: (i) ascorbate is an extremely effective antioxidant for LDL containing a-tocopherol (a-TOH); (i) in the presence of a-TOH and in the absence of both ascorbate and ubiquinol 10 (QloH2), oxidation of LDL occurs via a free radical chain; (ii)

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“…Such studies were usually carried out in homogeneous solution, the main exceptions being some studies in micelles by our laboratory (26) and by others (41,42). The determirzntiotz of' c~tztiosidntzt ~zctivities it7 membrane systems is tr mow sigtiifictlrzt but n tn~tch tnore difficult es~>er-itnerlt.…”

Section: )mentioning

confidence: 99%

“…As a result, molecules without this chain but possessing the hydroxychroman system (2a,4cr,Sa) are more active antioxidants than a-tocopherol, and this may in part be due to their greater freedom of motion. Diffusion control between micelles is cited to cause reduced antioxidant activity of lipopholic phenols such as atocopherol (41). Also, it is interesting to note that PMHC, 20, is able to transfer between liposomal membranes whereas diffusion of a-tocopherol between membranes is suppressed (45).…”

Section: D~~i L S I O N Li~nititlg Eflects Of Bilayers Otz Ylletlolicmentioning

confidence: 99%

1992 Syntex Award Lecture Model biomembranes: quantitative studies of peroxidation, antioxidant action, partitioning, and oxidative stress

Barclay¹

1993

Can. J. Chem.

173

140

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Tlris lecrure is dedicated ro Keith Irzgolcl L. R. C . BARCLAY. Can J. Chem. 71, 1 (1993). This review outlines a decade of research that employs quantitative kinetic methods of autooxidation to phospholipids aggregated into membranes. The classical rate law for autoxidation: was found to apply to heterogeneous systems of bilayers and micelles, where k, and 2k, are the rate constants for chain propagation and termination, respectively, and R,, the rate of chain initiation, is controlled b thermal initiators. The oridizobility of a typical lipid chain, linoleate 18:2, at 30°C was similar (0.02-0.04 M -" S -'~) in different media (solution, micelles, bilayers) and for different procedures using water-soluble or lipid-soluble initiators and inhibitors. A reduction in the absolute rate constant for termination, 2k,, by a hundredfold in bilayers of dilinoleoylphosphatidyl choline (DLPC) compared to that in rerr-butyl alcohol solution, and a drop in the k, by a factor of five are interpreted in terms of diffusion of polarized peroxyl radicals from the hydrophobic bilayer phase to the aqueous surface, where peroxyls are strongly solvated by water. Such phenomena may also account for significant changes as observed by "P NMR spectra in bilayer lamellar structure accompanying extensive peroxidation. Analysis of the hydroperoxides formed by peroxidation of mixed bilayers of DLPC + DPPC (16:O) initiated by a water-soluble initiator, azobis(2-amidinopropane.Hc1) (ABAP), showed a linear trend between the ratio of cis,trarzs to trnrls,frarzs geometrical isomeric hydroperoxides and [DPLC] consistent with a peroxidation mechanism proposed in homogeneous solution.The antioxidant activities, k,,,, of three classes of antioxidants: (a) polyalkyl-6-hydroxychromans (e.g., vitamin E), (0) polyalkyl-4-methoxyphenols, and (c) trialkylphenols, were measured in DLPC membranes. The results show an overall leveling and depression of k,,,', values in DLPC membranes in the series ( a ) (by several orders of magnitude), (b), and (c) compared to known values in solution in chlorobenzene. In aqueous bilayers it is proposed that kin,, values are attenuated by hydrogen bonding by water at both the p a r a ether oxygen and phenolic groups-. Restricted diffusion (e.g., of a-tocopherol) may also reduce antioxidant activities in membranes. A synergistic effect between ascorbic acid and atocopherol was discovered under conditions of inhibited peroxidation of linoleate in SDS micelles. The natural peptide glutathione, GSH, however, acts as a co-nrztio.ri~111rt with vitamin E by trapping peroxyls in the aqueous phase.Solid cholesterol was found to partition directly into PC lipsomes by shaking, above or below the phase transition temperature, and membrane-bound cholesterol, unlike the solid, undergoes facile peroxidation. A water-soluble form of c--tocopherol complexed with bovine serum albumin (a-toc:BSA) is an effective antioxidant for autoxidations of linoleate in SDS micelles. In contrast, a-toc:BSA required a long equilibration time (e.g., 12 h) wi...

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Inhibition kinetics of chain-breaking phenolic antioxidants in SDS micelles. Evidence that intermicellar diffusion rates may be rate-limiting for hydrophobic inhibitors such as .alpha.-tocopherol

Cited by 143 publications

References 1 publication

Mass Transport Phenomena in Lipid Oxidation and Antioxidation

Mass Transport Phenomena in Lipid Oxidation and Antioxidation

Autoxidation of lipids and antioxidation by alpha-tocopherol and ubiquinol in homogeneous solution and in aqueous dispersions of lipids: unrecognized consequences of lipid particle size as exemplified by oxidation of human low density lipoprotein.

1992 Syntex Award Lecture Model biomembranes: quantitative studies of peroxidation, antioxidant action, partitioning, and oxidative stress

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