Isomeric discrimination of kaempferol versus luteolin by online energy-resolved mass spectrometry / 中国中药杂志

Isomers are widely distributed in Chinese herbal medicines,and can be discriminated by energy-resolved mass spectrometry( ER-MS). However,ER-MS was performed through direct injection of reference compounds with syringe pump,which encountered a significant technical barrier for high-throughput and automated measurements. Herein,online ER-MS was conducted using LC-MS platform,and a pair of isomers,kaempferol vs luteolin,were employed as a case study to illustrate and assess the utility of online ER-MS for isomeric discrimination. High-resolution tandem mass spectrometry data of both flavonoids were acquired on LC-QE-Orbitrap-MS,and the fragmentation pathways responsible for the primary fragment ions were proposed. The primary signal in MS1 occurred at m/z 285( [M-H]-),and the primary signals of either compound generated by retro-Diels-Alder fragmentation were observed at m/z 151 and 133. The spectral information was subsequently transferred onto LC-Qtrap-MS platform to carry out online ER-MS. Two precursor-to-product ion transition candidates were constructed as m/z 285>151 and 285>133,and either afterward derived a set of pseudo-ion transitions( PITs) and so forth,exactly corresponding to a series of progressive collision energies( eg-5,-8,-11 e V,and so on). All PITs were typed into the monitoring list of multiple reaction monitoring program to generate the peak area datasets. Either dataset was normalized using the highest values in the set and imported into Graph Pad Prism software to plot the Gaus-sian-shaped curve that was termed as the break-down graph. The apex of the regressive curve was termed as optimal collision energy( OCE). The OCE values corresponding to m/z 285>151 were calculated as-29. 06 e V and-35. 71 e V for kaempferol and luteolin,respectively. In the case of m/z 285>133,the OCEs were yielded as-44. 15 e V for kaempferol and-49. 01 e V for luteolin. With re-ference to their chemical structures,the location of hydroxyl group was regarded to be responsible for the differences of either m/z 285>151 or 285>133 between the isomers,attributing to their different bond properties. Above all,online ER-MS offers an eligible tool for isomeric discrimination,and provides meaningful information for the accurate chemical composition characterization based on LC-MS,which is not limited to Chinese herbal medicines.

Identification of active components in Longxue Tongluo Capsules against ischemic brain injury based on component-activity relationship / 中国中药杂志

Ten fractions(A-J) were prepared by separation of Longxue Tongluo Capsules(LTC) by using silica gel column chromatography and orthogonal experimental design,showing similar chemical profiles with different abundances of peaks.These ten samples were assessed with UHPLC-QE OrbitrapHRMS for 97 common peaks.For the pharmacological activity experiment,three kinds of in vitro cell models including lipopolysaccharide(LPS)-induced BV-2 microglial cells NO release model,oxygen-glucose deprivation/reoxygenation(OGD/R)-treated HUVEC vascular endothelial cells injury model,and OGD/R-treated PC-12 nerve cells injury model were employed to evaluated the bioactivity of each fraction.Based on the contribution of each identified component,grey relation analysis and partial least squares(PLS) analysis were performed to establish component-activity relationship of LTC,identify the potential active components.After that,validation of the potential active components in LTC was carried out by using the same models.The results indicated that 4 phenolic compounds including 7,4'-dihydroxyhomoisoflavanone,loureirin C,4,4'-dihydroxy-2,6-dimethoxydihydrochalcone,and homoisosocotrin-4'-ol,might be the active components for anti-neuroinflammation effect;five phenolic compounds such as 3,5,7,4'-tetrahydroxyhomoisoflavanone,loureirin D,7,4'-dihydroxyhomoisoflavane,and 5,7-dihydroxy-4'-methoxy-8-methyflavane,might have positive effects on the vascular endothelial injury;three phenolic compounds including 5,7,4'-trihydroxyflavanone,7,4'-dihydroxy-5-methoxyhomoisoflavane,and loureirin D,might be the active components in LTC against neuronal injury.