- Novel galactolipids from the leaves of Ipomoea batatas L.: Characterization by liquid chromatography coupled with electrospray ionization-quadrupole time-of-flight tandem mass spectrometry
-
Sixteen novel and ten known galactolipids have been isolated and characterized from the leaves of Ipomoea batatas L. (sweet potato) using an analytical method based on high-performance liquid chromatography coupled with electrospray ionization-quadrupole
- Napolitano, Assunta,Carbone, Virginia,Saggese, Paola,Takagaki, Kinya,Pizza, Cosimo
-
experimental part
p. 10289 - 10297
(2009/10/02)
-
- One-electron reduction of methanesulfonyl chloride. The fate of MeSO 2CI?- and MeSO2? intermediates in oxygenated solutions and their role in the cis-trans isomerization of mono-unsaturated fatty acids
-
The one-electron reduction of methanesulfonyl chloride (MeSO2Cl) leads, in the first instance, to an electron adduct MeSO2Cl ?- which lives long enough for direct detection and decays into sulfonyl radicals MeSO2? and Cl-, with k = 1.5 × 106 s-1. Both, MeSO2Cl ?- and MeSO2? showed a similar absorption in the UV with λmax of 320 nm. In the presence of oxygen, MeSO 2Cl?- transfers an electron to O2 and establishes an equilibrium with superoxide. The rate constant for the forward reaction was measured to 4.1 × 109 M-1 s -1, while for the back reaction only an interval of 1.7 × 105 to 1.7 × 106 M-1 s-1 could be estimated, with a somewhat higher degree of confidence for the lower value. This corresponds to an equilibrium constant in the range of 2.4 × 10 3 to 2.4 × 104. With reference to E°(O 2/O2?-) = -155 mV, the redox potential of the sulfonyl chloride couple, E°(MeSO2Cl/MeSO2Cl ?-), thus results between being equal to -355 and -414 mV (vs NHE). MeSO2Cl?- reduces (besides O2) 4-nitroacetophenone. The underlying electron transfer took place with k = 1.5 × 109 M-1 s-1, corroborating an E° for the sulfonyl chloride couple significantly exceeding the above listed lower value. The MeSO2? radical added to oxygen with a rate constant of 1.1 × 109 M-1 s-1. Re-dissociation of O2 from MeSO2OO? occurred only very slowly, if at all, that is, with k ? 105 s-1. MeSO 2? radicals can act as the catalyst for the cis-trans isomerization of several Z- and E-mono-unsaturated fatty acid methyl esters in homogeneous solution. The effectiveness of the isomerization processes has been addressed, and in the presence of oxygen the isomerization is completely suppressed.
- Tamba, Maurizio,Dajka, Katalin,Ferreri, Carla,Asmus, Klaus-Dieter,Chatgilialoglu, Chryssostomos
-
p. 8716 - 8723
(2008/02/13)
-