Direct ESR detection of pentadienyl radicals and peroxyl radicals in lipid peroxidation: mechanistic insight into regioselective oxygenation in lipoxygenases

Well-resolved ESR spectra of free pentadienyl radicals have been observed under photoirradiation of di-tert-butylperoxide (Bu(t)OOBu(t)) and polyunsaturated fatty acids in the absence of O(2), allowing us to determine the hfc values. The hfc values of linoleyl radical indicate that the spin density is the largest at the C-11 position. The linoleyl radical is readily trapped by O(2) to produce the peroxyl radical (11-HPO.) in which O(2) is added mainly at the C-11 position of the pentadienyl radical as indicated by the comparison of the ESR spectra of peroxyl radicals derived from linoleic acid and [11,11-(2)H(2)]linoleic acid. The peroxyl radical (13-HPO.), which is initially formed by the hydrogen abstraction from 13-(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid (13-HPOD) by Bu(t)O., is found to isomerize to 11-HPO. via removal of O(2) from 13-HPO. and addition of O(2) to linoleyl radical to produce 11-HPO. . This finding supports an idea of O(2) entering via a specific protein channel, which determines the stereo- and regiochemistry of the biradical combination between O(2) and linoleyl radical in lipoxygenases.     

High-performance liquid chromatographic determination of linoleic acid peroxide-derived radicals using electrochemical detection

High-performance liquid chromatography-electrochemical detection (HPLC-ED) was applied to detect 13-hydroperoxide octadecadienoic acid (13-HPODE)-derived radicals such as the pentyl radical and octanoic acid radical. The 13-HPODE-derived radicals were successfully detected using HPLC-ED by the combined use of the spin-trapping technique with alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN). The 4-POBN-pentyl radical adduct was detected at the retention time of 18.2 +/- 0.3 min on the elution profile of HPLC-ED with an ODS column (15 cm x 4.6 mm I.D.) using a flow-rate of 1.0 ml/min with 50 mM ammonium acetate in 29% (v/v) aqueous acetonitrile. The 4-POBN-octanoic acid radical adduct was also detected at the retention time of 13.7 +/- 0.7 min using a flow-rate of 1.0 ml/min with 50 mM ammonium acetate in 14% (v/v) aqueous acetonitrile. The concentrations of the 4-POBN radical adducts were determined using HPLC-ED without an internal standard. HPLC-ED is 100 times as sensitive as HPLC-electron spin resonance (ESR) under the ESR and ED conditions employed here. Even 1.8 pmol of the 4-POBN-pentyl (or octanoic acid) radical adduct was detectable using     

Analysis of FeII-mediated decomposition of a linoleic acid-derived lipid hydroperoxide by liquid chromatography/mass spectrometry

Intracellular Fe(II), which is up-regulated during oxidative stress and during iron overload, induces the formation of a hydroxyl radical by Fenton chemistry. The hydroxyl radical can convert the prototypic omega-6 polyunsaturated fatty acid, linoleic acid, to 13-hydroperoxy-9,11-(Z,E)-octadecadienoic acid (13-HPODE). Cyclooxygenases can also convert linoleic acid to 13(S)-HPODE during oxidative stress. Subsequent Fe(II)-mediated decomposition to protein- and DNA-reactive bifunctional electrophiles was examined by normal-phase liquid chromatography (LC)/atmospheric pressure chemical ionization (APCI)/mass spectrometry. The potential individual bifunctional electrophiles trans-4,5-epoxy-2(E)-decenal (EDE), cis-EDE, 4-oxo-2(E)-nonenal (ONE) and 4-hydroxy-2(E)-nonenal (HNE) exhibited protonated molecular ions at m/z 169, 169, 155 and 157, respectively. The MH(+) ion at m/z 173 for 4-hydroperoxy-2(E)-nonenal (HPNE) was very weak with an ion corresponding to the loss of OH at m/z 156 as the major ion in the APCI mass spectrum. The bifunctional electrophiles were all separated under normal-phase LC conditions. Interestingly, ions corresponding to ONE and HNE were detected at the same retention time as HPNE, suggesting that it decomposed in the source of the mass spectrometer to ONE and HNE. All five bifunctional electrophiles were formed when 13-HPODE was treated with 50 microM Fe(II). At this concentration of Fe(II), the addition of vitamin C resulted in increased bifunctional electrophile formation. At higher concentrations of Fe(II) (500 microM to 2 mM), no HPNE was detected and there was no additive effect of vitamin C. Additional experiments with synthetic HPNE revealed that it was quantitatively converted to a mixture of ONE and HNE by Fe(II). The HNE is thought to arise from a one-electron reduction of an alkoxy radical derived from HPNE. In contrast, ONE can arise through an alpha-cleavage of the HPNE-derived alkoxy radical or by direct dehydration of HPNE.     

Thioridazine induces immediate and delayed erythema in photopatch test

Thioridazine is a phenothiazine derivative that has been used as an antipsychotic; it rarely causes photosensitization. However, we noticed that this drug induced an erythematous reaction in a photopatch test. Six volunteers were patch tested with various concentrations of thioridazine and irradiated with a range of UVA doses, and the time courses of the color of and blood flow to the test sites were monitored. The free-radical metabolites of thioridazine generated under UVA irradiation and its effects on ascorbate radical formation were examined with an electron paramagnetic resonance (EPR) spectrometer in vitro. As a result, immediate erythema developed during UVA irradiation in most subjects when 1% thioridazine was applied for 48 h and irradiation doses were higher than 4 J cm(-2). Another peak of erythematous reaction was observed 8-12 h after irradiation. The in vitro examination detected an apparent EPR signal, which appeared when 2 mM thioridazine in air-saturated phosphate buffer was irradiated with UVA, whereas this reaction was attenuated under anaerobic conditions. The EPR signal of the ascorbate radical was augmented under both aerobic and anaerobic conditions. Thioridazine-derived oxidants and/or thioridazine radicals generated during UVA irradiation seem to play an important role in this unique phototoxic reaction.     

Reactions of hydro(pero)xy derivatives of polyunsaturated fatty acids/esters with nitrite ions under acidic conditions. Unusual nitrosative breakdown of methyl 13-hydro(pero)xyoctadeca-9,11-dienoate to a novel 4-nitro-2-oximinoalk-3-enal product

13(S)-hydroperoxy- and 13(S)-hydroxyoctadeca-9,11-dienoic acids (1a/b), 15(S)-hydroperoxy- and 15(S)-hydroxyeicosa-5,8,11,13-tetraenoic acids (2a/b), and their methyl esters reacted smoothly with NO2- in phosphate buffer at pH 3-5.5 and at 37 degrees C to afford mixtures of products. 1b methyl ester gave mainly the 9-nitro derivative 3b methyl ester (11% yield) and a peculiar breakdown product identified as the novel 4-nitro-2-oximinoalk-3-enal derivative 4 methyl ester (15% yield). By GC-MS hexanal was also detected among the products. Structures 3b and 4 methyl esters were secured by 15N NMR analysis of the products prepared from 1b methyl ester upon reaction with Na15NO2. 4 methyl ester (14% yield) was also obtained from 1a methyl ester along with the nitrated hydroperoxy derivative 3a methyl ester (10% yield). Under the same conditions, 2a/b methyl esters gave mainly the corresponding nitrated derivatives 5a/b, with no detectable breakdown products, whereas the model compound (E,E)-2,4-hexadienol (6) afforded two main nitrated derivatives identified as 7 and 8. A reaction pathway for 1a/b methyl esters was proposed involving conversion of nitronitrosooxyhydro(pero)xy intermediates which would partition between two competing routes, viz., loss of HNO2, to give 3a/b methyl esters, and a remarkably facile fission leading to 4 methyl ester and hexanal.     

Identification of oxidative processes during simulated mastication of uncooked foods using electron paramagnetic resonance spectroscopy

Electron paramagnetic resonance (EPR) spectroscopy is used to measure directly the generation of free radicals during a simulation of the mastication process. This involves the gentle grinding of the food product in the presence of a spin trap, a molecule which reacts selectively with unstable free radicals to generate (more) stable radical adducts, which can then be characterised. With mushrooms of the Agaricus family, adducts consistent with a carbon-centred radical are seen with a wide range of spin traps and this radical has been confirmed as 4-(hydroxymethyl)phenyl. In plant tissues that are rich in ascorbic acid, this molecule competes successfully with spin traps for the free radicals and the (monodehydro)ascorbate radical, formed by the 1-electron oxidation of ascorbic acid, is seen in the EPR spectra. However, with >50% of the plant tissue samples studied in the present experiment, free radicals resulting from oxidation of the spin traps were observed. The formation of such molecules, for which oxygen was found to be necessary, requires the existence of powerful oxidation processes as the plant tissue is broken down. Such pro-oxidant behaviour is contrary to the popular assumption that the beneficial effects of uncooked plant tissues are the result of their high levels of anti-oxidant molecules.     

EPR of free radicals formed from 3-hydroxyesculetin and related derivatives

EPR spectroscopy of 3-hydroxyesculetin (1, solid and in solution) and of the radicals formed during the aerobic oxidation of alkaline solutions of 1 and related compounds was investigated. 1 in the solid state was studied by pulsed EPR experiments and showed a radical character. The aerobic oxidation of alkaline solutions of 1 was also followed by EPR spectroscopy. A ring contraction occurred leading to a 5,6-dihydroxybenzofuran-2-carboxylate radical. The autoxidation of an alkaline solution of (Z)-3-(3,4-dihydroxyphenyl)-2-hydroxypropenoic acid allowed the observation of a spectrum attributable to 5,6-dihydroxybenzofuran-3-one-2-carboxylate radical. The formation mechanisms of these radicals are discussed.     

Liquid chromatography/mass spectrometry analysis of bifunctional electrophiles and DNA adducts from vitamin C mediated decomposition of 15-hydroperoxyeicosatetraenoic acid

Reactive oxygen species convert the omega-6 polyunsaturated fatty acid arachidonic acid into 15-hydroperoxy-5,8,11,13-(Z,Z,ZE)-eicosatetraenoic acid (15-HPETE). Cyclooxygenases and lipoxygenases can also convert arachidonic acid into 15-HPETE. Vitamin C mediated decomposition of 15(S)-HPETE to protein- and DNA-reactive bifunctional electrophiles was examined by normal-phase liquid chromatography/atmospheric pressure chemical ionization/mass spectrometry (LC/APCI-MS). The individual bifunctional electrophiles, trans-4,5-epoxy-2(E)-decenal (t-EDE), cis-4,5-epoxy-2(E)-decenal (c-EDE), 4-oxo-2(E)-nonenal (ONE), and 4-hydroxy-2(E)-nonenal (HNE), exhibited protonated molecules at m/z 169, 169, 155, and 157, respectively. The MH+ ion at m/z 173 for 4-hydroperoxy-2(E)-nonenal (HPNE) was very weak with an ion corresponding to the loss of OH at m/z 156 as the major ion in the APCI mass spectrum. The bifunctional electrophiles were all separated under normal-phase LC conditions. All five bifunctional electrophiles were formed when 15-HPETE was treated with vitamin C. The LC/MS-based methodology showed that t-EDE was the major bifunctional electrophile formed during vitamin C mediated 15(S)-HPETE decomposition. Stable isotope dilution LC/MS studies revealed that this did not result in the formation of increased levels of unsubstituted etheno-dGuo adducts in calf thymus DNA when compared with 13(S)-hydroperoxy-9,10-(Z,E)-octadecadienoic acid [13(S)-HPODE], a lipid hydroperoxide derived from linoleic acid. However, the formation of heptanone-etheno-dGuo adducts in calf thymus DNA was reduced when compared with the 13(S)-HPODE. This was attributed to the reduced formation of ONE from 15-HPETE when compared with its formation from 13-HPODE. In contrast to reactions with dGuo or DNA conducted using 13(S)-HPODE, no carboxy-containing adducts were observed with 15(S)-HPETE.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—XL PHOTOLYSIS OF CHLORPROMAZINE METABOLITES: A SPIN-TRAPPING STUDY

Abstract. The photochemistry of chlorpromazine (CPZ) and its metabolites, 7-hydroxychlorpromazine (7OHCPZ), desmethylchlorpromazine (DCPZ), didesmethylchlorpromazine (DDCPZ) and chlorpromazine sulfoxide (CPZSO) was studied by the spin trapping technique with 2-methyl-2-nitrosopropane and 5,5-dimethyl-l-pyrroline- N -oxide. 7-Hydroxychlorpromazine generated hydroxyl radicals when excited at 330 nm under either anaerobic or aerobic conditions. 7-Hydroxychlorpromazine, DCPZ and DDCPZ all underwent dechlorination upon photoexcitation which was enhanced in the absence of air. Chlorpromazine sulfoxide did not undergo photodechlorination but instead generated a high yield of the hydroxyl radical. A comparison among CPZ and its derivatives shows that the yield of the photodechlorinated product is directly related to the degree of phototoxicity. This suggests photodechlorination is an important factor in the phototoxicity of CPZ and its metabolites.     

Free radicals and radical anions in a series of telluroxanthene derivatives

In the one-electron reduction of telluroxanthyl or telluroxanthone perchlorates, stable 9-aryltelluroxanthyl radicals and telluroxanthone radical anion are formed. An EPR study of the distribution of spin density in such radicals gives evidence that the nature of the heteroatoms in the xanthyl fragments has an insignificant influence on the distribution of the spin density.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1196–1100, September, 1988.     

PHOTOSENSITIZATION BY ANTICANCER AGENTS—10. ortho-SEMIQUINONE AND SUPEROXIDE RADICALS PRODUCED DURING ANTHRAPYRAZOLE-SENSITIZED OXIDATION OF CATECHOLS

Photosensitized oxidation of catechol, 3,4-dihydroxybenzoic acid (DHBA), 3,4-dihydroxy-dihydrocinnamic acid (DHCA), and 3,4-dihydroxy-phenylalanine (DOPA) by novel anticancer agents, anthrapyrazoles (AP), has been studied employing EPR and the spin trapping technique. The formation of o-semiquinone radicals, the one-electron oxidation products of the catechols, stabilized in the form of zinc ion complexes, has been demonstrated. Rate constants for the disproportionation of the semiquinone radical/Zn2+ complexes in (DMSO)/acetate buffer (pH 4.5, 1:1 vol/vol; 100 mM Zn2+) mixture have been determined to be 0.35 x 10(4), 14 x 10(4), 8.8 x 10(4) and 3 x 10(4) M-1 s-1 for catechol, DHBA, DHCA and DOPA respectively. The presence of oxygen enhanced rather than inhibited the photogeneration of the o-semiquinone radicals and facilitated their EPR detection. The EPR spectrum of the superoxide radical adduct with the spin trap 5,5-dimethyl-1-pyrroline-N-oxide was observed for the first time during photosensitized oxidation of the catechols in acidic aqueous solutions and in DMSO/acetate buffer mixture.     

Radicaloid-type oxidative decomposition of beer bittering agents revealed

trans-Isohumulones, dihydroisohumulones, tetrahydroisohumulones, and humulinones, which are important hop-derived flavor components of beer, were found, by using electrolysis of organic solutions, to be stable against oxidation, like weak acids; however, they are readily oxidized in their anionic forms as present in beer. Oxygen- and carbon-centered radicals were formed by oxidation and identified by using spin trapping under aerobic and anaerobic conditions, followed by EPR (electron paramagnetic resonance) spectroscopy. Generated radicals were reactive, most likely degrading into products lacking the tricarbonyl chromophore; this is typical of five-membered-ring hop derivatives. Thus, flavor-active beer constituents may degrade oxidatively in the absence of oxygen, thereby leading to reaction products that escape UV detection.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—XL PHOTOLYSIS OF CHLORPROMAZINE METABOLITES: A SPIN-TRAPPING STUDY

Abstract. The photochemistry of chlorpromazine (CPZ) and its metabolites, 7-hydroxychlorpromazine (7OHCPZ), desmethylchlorpromazine (DCPZ), didesmethylchlorpromazine (DDCPZ) and chlorpromazine sulfoxide (CPZSO) was studied by the spin trapping technique with 2-methyl-2-nitrosopropane and 5,5-dimethyl-l-pyrroline-N-oxide. 7-Hydroxychlorpromazine generated hydroxyl radicals when excited at 330 nm under either anaerobic or aerobic conditions. 7-Hydroxychlorpromazine, DCPZ and DDCPZ all underwent dechlorination upon photoexcitation which was enhanced in the absence of air. Chlorpromazine sulfoxide did not undergo photodechlorination but instead generated a high yield of the hydroxyl radical. A comparison among CPZ and its derivatives shows that the yield of the photodechlorinated product is directly related to the degree of phototoxicity. This suggests photodechlorination is an important factor in the phototoxicity of CPZ and its metabolites.     

Identification of free radicals induced by UV irradiation in collagen water solutions

Electron paramagnetic resonance (EPR) method has shown that hydrogen atoms and acetic acid free radicals appear in surrounding acetic acid-water solution of collagen under ultraviolet (UV) irradiation. These free radicals interact with the collagen molecule; consequently, seven superfine components of EPR spectrum with the split of aH = 11.3G and g-factor 2.001 appear. It is assumed that this spectrum is related to the free radical occurred on the proline residue in collagen molecule. In order to discover .OH hydroxyl radicals even in minor concentration, spin trap 5.5-dimethyl-1-pyrroline N-oxide (DMPO) has been applied. During the irradiation of collagen water solution in the presence of spin trap, EPR spectrum of the DMPO/.OH adduct has not been identified, while the above mentioned spectrum has been observed once the hydrogen peroxide H2O2 and FeSO4 were added to the sample. That means that water photolysis does not take place in collagen water-solution due to UV irradiation. It was suggested that occurrence of hydrogen radical is connected with the electron transmission to the hydrogen ion. The possible source of free electrons can be aromatic residues, photo ionization of which takes place in collagen molecule due to UV irradiation.     

Model systems for poly(acrylic acid) main-chain radicals based on the Kemp's triacid framework

Kemp's triacid (KTA) and cyclohexane tricarboxylic acid (CTA) are small-molecule model systems for acrylic acid polymers, having the same functionalities and stereoregularities as isotactic poly(methacrylic acid) (PMAA) and poly(acrylic acid) (PAA), respectively. As part of an ongoing investigation of radicals produced by photolysis of acrylic polymers, the photochemistry and free radicals from the model systems have been studied using time-resolved EPR spectroscopy as a function of temperature and pH. Radicals are created by direct photolysis of the acids at 248 nm or by sensitized photo-oxidation using quinone triplet states at 308 nm. The two methods of radical production lead to different chemically induced electron spin polarization (CIDEP) patterns in the ensuing radicals, which are simulated and discussed. Well-resolved spectra are obtained at all temperatures for the model system radicals, which are determined to be in the slow motion condition. DFT calculations of the model system radicals are presented and discussed in support of the experimental data.     

Influence of conformation on the EPR spectrum of 5,5-dimethyl-1-hydroperoxy-1-pyrrolidinyloxyl: a spin trapped adduct of superoxide

Spin trapping, a technique used to characterize short-lived free radicals, consists of using a nitrone or nitroso compound to "trap" an unstable free radical as a long-lived aminoxyl that can be characterized by EPR spectroscopy. The resultant aminoxyl exhibits hyperfine splitting constants that are dependent on the spin trap and the free radical. Such is the case with 2,2-dimethyl-5-hydroxy-1-pyrrolidinyloxyl (DMPO-OH) and 2,2-dimethyl-5-hydroperoxy-1-pyrrodinyloxyl (DMPO-OOH) whose hyperfine splitting constants, A(N) = A(H) = 14.9 G and A(N) = 14.3 G, A(H)(beta) = 11.7 G, and A(H)(gamma) = 1.25 G, respectively, have been used to demonstrate the generation of HO(*) and O(2)(*)(-). However, to date, the source of the apparent A(H)(gamma) hyperfine splitting in DMPO-OOH is not known. We consider three possible explanations to account for the unique EPR spectrum of DMPO-OOH. The first is that the gamma-splitting arises from one of the hydrogen atoms at either carbon 3 or carbon 4 of DMPO-OOH. The second is that the gamma-splitting originates from the hydrogen atom of DMPO-OOH. The third is that the conformational properties of DMPO-R change upon going from DMPO-OH to DMPO-OOH. Experimental and theoretical chemical approaches as well as EPR spectral modeling were used to investigate which of these hypotheses may explain the asymmetric EPR spectrum of DMPO-OOH. From these studies it is shown that the 12-line EPR spectrum of DMPO-OOH results not from any proximal hydrogen, but from additional conformers of DMPO-OOH. Thus, the 1.25 G hyperfine splitting, which has been assigned as a gamma-splitting, is actually from two individual EPR spectra associated with different conformers of DMPO-OOH.     

Generation,Spectroscopic Characterization by EPR,and Decay of a Pyranine‐Derived Radical

The pyraninoxyl radical is readily formed from the MnO₂‐promoted oxidation of pyranine. The free radical can be formed in high concentrations (mM ), and presents a characteristic EPR spectrum that indicates a high spin‐density delocalization. It is relatively stable under nitrogen (half‐life ca. 50 min) but readily decays in presence of O₂. In spite of its high stability, the radical readily reacts with antioxidants (phenols and ascorbic acid) with a partial recovery of the parent pyranine. High concentrations of the pyraninoxyl radical (ca. 9 μM ) are present when pyranine is exposed to a free radical source (10 mM 2,2′‐azobis[2‐amidinopropane], 37°). The fact that these radicals readily react with antioxidants (ascorbic acid and caffeic acid) supports the proposal that protection by antioxidants of peroxyl radical‐promoted pyranine bleaching is mainly due to the occurrence of a repair mechanism.     

EPR parameters of amino acid radicals in P. eryngii versatile peroxidase and its W164Y variant computed at the QM/MM level

Quantum mechanics/molecular mechanics (QM/MM) methods, employing density functional theory (DFT), have been used to compute the electron paramagnetic resonance (EPR) parameters of tryptophan and tyrosyl radical intermediates involved in the catalytic cycle of Pleurotus eryngii versatile peroxidase (VP) and its W164Y variant, respectively. These radicals have been previously experimentally detected and characterized both in the two-electron and one-electron activated forms of the enzymes. In this work, the well-studied W164 radical in VP has been chosen for calibration purposes because its spectroscopic properties have been extensively studied by multifrequency EPR and ENDOR spectroscopies. Using a B3LYP/CHARMM procedure, appropriately accounting for electrostatic, such as hydrogen bonding, and steric environmental interactions, a good agreement between the calculated and measured EPR parameters for both radicals has been achieved; g-tensors, hyperfine coupling constants (hfcc) and Mulliken spin densities have been correlated to changes in geometries, hydrogen bond networks and electrostatic environment, with the aim of understanding the influence of the protein surroundings on EPR properties. In addition, the present calculations demonstrate, for VP, the formation of a neutral tryptophan radical, hydrogen bonded to the nearby E243, via a stepwise electron and proton transfer with earlier involvement of a short-lived tryptophan cationic species. Instead, for W164Y, the QM/MM dynamics simulation shows that the tyrosine oxidation proceeds via a concerted electron and proton transfer and is accompanied by a significant reorganization of residues and water molecules surrounding the tyrosyl radical.     

Effects of pulsed ultrasound on the adsorption of n-alkyl anionic surfactants at the gas/solution interface of cavitation bubbles

Sonolysis of argon-saturated aqueous solutions of the nonvolatile surfactants sodium dodecyl sulfate (SDS) and sodium 1-pentanesulfonate (SPSo) was investigated at three ultrasonic frequencies under both continuous wave (CW) and pulsed ultrasound. Secondary carbon-centered radicals were detected by spin trapping using 3,5-dibromo-4-nitrosobenzenesulfonic acid (DBNBS) and electron paramagnetic resonance (EPR) spectroscopy. Following sonolysis, -*CH- radicals were observed for both surfactants under both sonication modes. Under CW at 354 kHz, the maximum plateau -*CH- radical yield was higher for SPSo than for SDS, indicating that SDS, which is more surface active under equilibrium conditions, accumulates at the gas/solution interface of cavitation bubbles to a lesser degree, compared with the less surface active surfactant, SPSo. However, after sonolysis (354 kHz) under pulsed ultrasound with a pulse length of 100 ms and an interval of 500 ms, the -*CH- radical yield at the plateau concentrations was higher for SDS than for SPSo due to increased amounts of SDS accumulation on the bubble surfaces. In contrast to the findings following sonolysis at 354 kHz, sonolysis of aqueous surfactant solutions at 620 kHz and 803 kHz showed a higher -*CH- radical yield for SDS compared with SPSo under CW but lower -*CH- radical yield with increasing pulsing interval, indicating a frequency dependence on accumulation. Results indicate that pulsing the ultrasonic wave has a significant effect on the relative adsorption ability of n-alkyl surfactants at the gas/solution surface of cavitation bubbles.     

Macrolides from the scent glands of the tropical butterflies Heliconius cydno and Heliconius pachinus

The four major components present in scent gland extracts of the male Costa Rica longwing butterflies Heliconius cydno and Heliconius pachinus were identified as 12- and 14-membered macrolides containing a C(18)-carbon skeleton. By use of micro-reactions and spectrometric examinations, structural proposals were made and subsequently proven by synthesis, using ring-closing-metathesis as the key steps. These macrolides, (9Z,11E,13S)-octadeca-9,11-dien-13-olide (5, S-coriolide), (9Z,11E,13S,15Z)-octadeca-9,11,15-trien-13-olide (6), (9Z,13S)-octadec-9-en-13-olide (13), and (9Z,11S)-octadec-9-en-11-olide (25), are biosynthetically obviously derived from oleic, linoleic, and linolenic acids. Their absolute configurations were determined by gas chromatographic investigations on chiral phases, showing all to possess (S)-configuration.