Comprehensive mass spectrum analysis of two flavone-6,8-C-di-glycosides and its application by high resolution electrospray ionization tandem mass spectroscopy in both negative and positive ion modes / 中国中药杂志

The tandem mass spectrum of apigenin-6,8-C-di-glucoside( 1) and apigenin-6-C-glucose-8-C-rhamnoside( 2) were obtained by high resolution electrospray ionization mass spectrometry( HR-ESI-MS/MS) in both positive and negative ion modes. The elemental composition of each ion was determined according to its accurate mass-to-charge,hence,the fragmentation pathways of each compound were proposed in both negative and positive ion modes. Comprehensive analysis of each ion and its proposed fragmentation pathways of the two compounds was initially conducted in both negative and positive ion mode HR-ESI-MS/MS to explore the diagnostic ions for flavone-6,8-C-di-glycosides and the characteristic ions for each compound and their cleavage rules. The results showed that a family of fragmentation ions with m/z 353,325,311,297 in ESI(-)-MS and m/z 355,325,307,295 in ESI( +)-MS could be the diagnostic ions of flavone-6,8-C-di-glycoside,and characteristic neutral loss could be assigned to glycosyl substitution,for example,neutral losses of C_4H_8O_4( 120),C_3H_6O_3( 90),C_2H_4O_2( 60) for glucoside substitution while neutral losses of C_4H_8O_3(104),C_3H_6O_2( 74),C_2H_4O( 44) for rhamnoside substitution. Furthermore,only one H_2O loss from mother ion( [M-H]-) was observed for 1 & 2 in ESI(-)-MS while five to six H2 O loss from mother ion( [M+H]+) was observed for 1 & 2 in ESI( +)-MS to produce a family of ions by subsequent loss of H_2O,which could be applied for glucosyl difference. The flavone-6,8-C-di-glycosides in both ESI( +)-MS and ESI(-)-MS showed the cleavage similarity at sugar substitutions. However,there were much more differences by the fragmentation pathways and neutral losses between ESI( +)-MS and ESI(-)-MS as following,hyperconjugation ions by subsequent loss of H_2O from precursor ions of flavone-6,8-C-di-glycosides in ESI( +)-MS were not observed in ESI(-)-MS; the subsequent neutral loss of CH_2O in ESI( +)-MS were rarely observed in ESI(-)-MS; the loss of CO only happen at C-ring of flavone ESI( +)-MS other than glycosyl position in ESI(-)-MS; the C4-chain neutral loss of flavone-6,8-C-di-glycosides happened at 8-C-glycosyl position other than at 6-C-glycosyl position. The above cleavage rules and diagnostic ions of ESI( +)-MS were successfully applied for the structure identification of 4 flavone-6 C,8 C-diglycosides from the stem extract of Dendrobium officinale as vicenin Ⅱ,vicenin Ⅰ,isoschaftoside,schaftoside as well as one flavone-O-glysoside named rutin,which were supported by ESI(-)-MS data as well.

Ion Abundance Ratios of Qualitative Analysis by GC-MS of 4 Common Drugs （Poisons / 法医学杂志

Objective To investigate the maximum allowable deviation of ion abundance ratios of characteristic fragment ions in common drugs （poisons） in blood by gas chromatography-mass spectrometry （GC-MS） method. Methods Four common drugs （poisons） （dichlorvos, phorate, diazepam and estazolam） were detected by GC-MS full scan mode after liquid-liquid extraction in two laboratories and under three chromatographic conditions. The deviations of ion abundance ratios of the four common drugs （poisons） in marked blood samples with concentrations of 0.5, 1.0, 2.0, 5.0 and 10.0 μg/mL were analyzed. At the same time, the false negative rates of ion abundance ratios were analyzed when the mass concentration was limit of detection （LOD）, 2LOD, limit of quantitation （LOQ） and 2LOQ, and the false positive rates of ion abundance ratios were analyzed with blank blood samples. Results Under the two laboratories, four common drugs （poisons） and three kinds of chromatography conditions, the differences in deviations of the ion abundance ratios of marked blood samples were not statistically significant （P>0.05）. More than 95% of the absolute deviations of the ion abundance ratios of the marked blood samples were within the range of ±10%, and more than 95% of the relative deviations were within the range of ±25%. In cases of low concentration （concentration less than 2LOQ） or low signal to noise ratio （3-15）, the false negative rate was less than 5% and the false positive rate was 0% when the relative deviation was greater than 50%. Conclusion The absolute deviations of ion abundance ratios of four common drugs （poisons） in marked blood samples are advised to have a determination range within ±10%, and the determination range of relative deviations within ±25%.

Electron spray ion trap mass spectrometry of isoflavones and isoflavone aglycones of Semen Sojae Praeparatum / 第二军医大学学报

Objective To analyze the fragments of 3 isoflavones and their isoflavone aglycones of Semen Sojae Praeparatum by electron spray ion trap mass spectrometry (ESI-MS), and to study the fragmentation pathway by major fragment ions. Methods Samples were fed into the instrument in the positive andnegative modes, and the fragments of the samples were yielded by multi-stage ion trap mass spectrometry (ESI-MS). The fragment ions of isoflavones and their isoflavone aglyconeswere analyzed. Results In the positive mode, ion peaks m/z 417, 255, 227, 199, 137, and 119 were detected for daidzin and daidzein; m/z 447, 285, 270, and 229 for glycitin and glycitein; and m/z 433, 271, 253, 243, 215, and 153 for genistin and genistein. In negative mode, ion peaksm/z 461, 415, 253, 225, 209, and 197 were detected for daidzin and daidzein; m/z 491, 445, 283, and 268 for glycitin and glycitein; and m/z 477, 269, 268, and 225 for genistin and genistein. Conclusion In the positive mode, daidzin and daidzein are fragmented by losing -Glu and -CO and Retro Diels-Alder (RDA) reaction; glycitin and glycitein are fragmented by losing -Glu, -CO, and -CH3; genistin and genistein are fragmented by losing -Glu, -CO, -H2O and RDA reaction. In negative mode, ions fragment [M+HCOO]- is produced by isoflavone glucosides, and daidzin and daidzein are fragmented by losing -Glu, -CO, -2CO and -CO2; glycitin and glycitein are fragmented by losing -Glu, -H, and -CH3; and genistin and genistein are fragmented by losing -Glu, -H, and-CO2.; glycitin amd glycitein are fragmented by losing -Glu-H, and -CH3; and genistin and genistein are fragmented by losing -Gli, -H, and -CO2.