Profiling of flavonoid conjugates in Lupinus albus and Lupinus angustifolius responding to biotic and abiotic stimuli.

Qualitative and quantitative composition of flavonoid and isoflavonoid glycosides as well as free aglycones in lupin seedlings (roots and aerial parts) grown under different light conditions or responding to infection with Pleiochaeta setosa, a fungus causing brown leaf spot, were monitored by liquid chromatography with UV and/or mass spectrometric detection. Both physical and biotic factors affected flavonoid and isoflavonoid levels in lupin tissues. Fungal infection evoked significant increase in the amounts of genistein, 2'-hydroxygenistein, and their prenylated derivatives that are thought to function as lupin phytoalexins. Effect on quantitative changes of glycosylated flavonoids and isoflavonoids in the roots and aerial parts was less significant. Moreover, different light conditions applied during seedling growth caused relative changes of flavonoid and isoflavonoid conjugates composition, especially in the leaves of white lupin plants. The chemical structures of flavonoid and isoflavonoid conjugates present in Lupinus angustifolius were elucidated. In addition to genistein and 2'-hydroxygenistein glycosides, flavonol conjugates were identified in leaves, while the composition of root isoflavonoids was similar to that of L. albus reported earlier.

Kaempferol and its glycosides in the seeds hair of Asclepias syriaca L.

The following flavonoid compounds have been isolated and identified from the seeds hair of Asclepias syriaca L.: kaempferol, kaempferol 3-O-beta-galactopyranoside, kaempferol 3-O-beta-xylopyranosyl (1 --> 2)-beta-galactopyranoside, kaempferol 3-O-beta-glucopyranosyl (1 --> 2)-beta-galactopyranoside, kaempferol 3-O-alpha-rhamnopyranosyl (1 --> 2)-beta-galactopyranoside. Their structures were established by acid hydrolysis, H2O2 oxidation and spectral analysis (UV, 1H, 3C NMR, MS).

Profiling changes in metabolism of isoflavonoids and their conjugates in Lupinus albus treated with biotic elicitor.

Liquid chromatography with ultraviolet and mass spectrometric detection was applied to monitor changes in profiles of isoflavonoid glycosides and free isoflavonoid aglycones in Lupinus albus L. Four isoflavonoid aglycones, fourteen isoflavonoid glycosides, four flavonol glycosides and flavone glycoside were identified in lupin tissue after LC/ESI/MS analyses. An elicitor preparation from purified yeast cell wall was used to inject the shoots of 3-week old seedlings or to infiltrate the cut lupin leaves. Qualitative and quantitative changes of isoflavonoids were measured at different time points after elicitation. In elicited lupin seedlings increased amounts of prenylated isoflavone aglycones were identified. The concentrations of glycosidic conjugates of isoflavones present in plant tissue were less affected.

Identification of photodegradation products of nilvadipine using GC-MS.

Nilvadipine (NV) photodegradation products have been analysed with gas chromatography-mass spectrometry (GC-MS). The photodegradation was carried out in the conditions recommended in the first version of the document issued by the International Conference on Harmonization (ICH), currently in force in the studies of photochemical stability of drugs and therapeutic substances. Methanol solutions of NV were irradiated with a high-pressure UV lamp - type HBO 200. The maximum intensity at the wavelength lambda = 365 nm was achieved by applying the interference filter and Wood's filter. Using the Reinecke salt as a chemical actinometer, apparent quantum yields of photodegradation were obtained, which after extrapolation to the zero time of irradiation gave the actual quantum yield ((phi = 7.58 x 10(-5). The structure of three nilvadipine photodegradation products was established, after mass spectra analysis of compounds registered during GC-MS carried out of irradiated nilvadipine solutions. The quantitative results of GC-MS analyses enabled to determination of the kinetic parameters of NV photodegradation, calculated from the dependence In c =f(t). Quantitatively the process was described with the calculated rate constant of decomposition (k), decomposition time of 50% of the compound (t0.5) and decomposition time of 10% of the compound (t0.1). The exposure of nilvadipine to UV light was found to lead to aromatization of the DHP ring and elimination of the HCN molecule.

Liquid secondary ion mass spectrometric investigation of ion-pair precipitates of some ethoxylates with barium tetraphenylborate

Liquid secondary ion mass spectrometry seems to be useful technique for the qualitative characterization of ion-pair precipitates of ethoxylates with barium tetraphenylborate. In the positive mode, barium complexes of ethoxylates were examined. In the negative mode, the ion signal of tetraphenylborate had 100% intensity relative to the matrix peaks. The low-resolution mass spectra were found to be suitable for checking the purity of ion-pair precipitates of ethoxylates with barium tetraphenylborate. On the basis of B/E mass spectra, the fragmentation routes of [M - H + Ba](+) ions are proposed. Copyright 2000 John Wiley & Sons, Ltd.

Application of mass spectrometry to structural identification of flavonoid monoglycosides isolated from shoot of lupin (Lupinus luteus L.).

Flavonoid glycosides constitute important group of plant secondary metabolites. This class of natural products play significant role in different physiological processes. A new methodological approach where mass spectrometric techniques are applied to structural studies of this class of compounds is presented. Four flavonoid O-monoglycosides and one C-monoglycoside were isolated from green parts of lupin (Lupinus luteus L.). Several different mass spectrometric techniques were applied to structural elucidation of isolated compounds. Desorption ionization mass spectrometry was used for registration of mass spectra of intact and derivatized (permethylated) flavonoid glycosides. In some cases electron impact mass spectra of permethylated compounds were also recorded. Methylated samples after methanolysis and further derivatization of free hydroxyl groups (methylation or acetylation) were analyzed with gas chromatography-mass spectrometry. Combined information drawn from the registered mass spectra enabled us to define molecular mass, structure of aglycones and sugars, and positions of glycosidic bonds on the aglycon. Structures of four flavonoid monoglycosides were elucidated as follows: genistein 7-O-glucoside (1), genistein 4'-O-glucoside (2), 2'-hydroxygenistein 7-O-glucoside (3), and apigenin or genistein 8-C-glycoside (5). For the fourth O-glycoside (4) only molecular mass and masses of the aglycone and sugar were estimated.