Trace determination and characterization of ginsenosides in rat plasma through magnetic dispersive solid-phase extraction based on core-shell polydopamine-coated magnetic nanoparticles

Enrichment of trace bioactive constituents and metabolites from complex biological samples is challenging.This study presented a one-pot synthesis of magnetic polydopamine nanoparticles(Fe3O4@-SiO2@PDA NPs)with multiple recognition sites for the magnetic dispersive solid-phase extraction(MDSPE)of ginsenosides from rat plasma treated with white ginseng.The extracted ginsenosides were characterized by combining an ultra-high-performance liquid chromatography coupled to a highresolution mass spectrometry with supplemental UNIFI libraries.Response surface methodology was statistically used to optimize the extraction procedure of the ginsenosides.The reusability of Fe3O4@-SiO2@PDA NPs was also examined and the results showed that the recovery rate exceeded 80%after recycling 6 times.Furthermore,the proposed method showed greater enrichment efficiency and could rapidly determine and characterize 23 ginsenoside prototypes and metabolites from plasma.In comparison,conventional methanol method can only detect 8 ginsenosides from the same plasma samples.The proposed approach can provide methodological reference for the trace determination and characterization of different bioactive ingredients and metabolites of traditional Chinese medicines and food.

Mechanism of Incompatible Herb Pairs, Panax ginseng and Veratrum nigrum L,： Material Basis and Metabolic Profiles of Ginsenosides in Rat Intestinal Bacteria

In traditional Chinese medicine theory, Panax ginseng and Veratrum nigrum L. is an important incompatible herb pair. Studies on the content variation of main components and the influences on the metabolism in rat intestinal bacteria are useful to understand the mechanism of incompatibility of this herb pairs. In this study, the content variation of ginsenosides and their metaboltic profiles in the extracts of P. ginseng and compatibility of P. ginseng with V. nigrum L. （G-V） were investigated using relative quantitative method of electrospray ionization mass spec- trometry （ESI-MS） and UPLC-MSn, respectively. The relative contents of most ginsenosides were reduced in the extract of G-V. Furthermore, ginsenosides Rbt, Rb2, Rc and Rd could be metabolized to Rd, F2 and C-K in rat in- testinal bacteria. The metabolic speeds ofRbl, Rb2 and Re in the G-V extracts at ratios of 10 ： 5, 10 ： 7 and 10 ： 10 and the metabolic rates of ginsenosides Rbb Rb2 and Rc to Rd, Rd to F2 in all compatibility extracts were lower than that in the P ginseng extract. In conclusion, this study illustrated the mechanism of effect-reducing by comparison of the relative contents and metabolic profiles of ginsenosides after compatibility of P ginseng and V. nigrum L.

α-Glucosidase immobilization on functionalized Fe_3O_4 magnetic nanoparticles for screening of enzyme inhibitors

Magnetic nanoparticles(MNPs) are widely used for the immobilization of enzyme owing to the unique properties such as good biocompatibility and rapid separation. Herein, we used Fe_3O_4 magnetic nanoparticles(Fe_3O_4 MNPs) as the carrier core with(3-aminopropyl)triethoxysilane(APTES)modification by our approach, in which a-glucosidase was stereoscopically immobilized on the surface of Fe_3O_4 MNPs via covalent binding. The result of immobilization was characterized by scanning electron microscope(SEM) and fourier transform-infrared spectroscopy(FT-IR). Then we optimized some key parameters of the immobilization reaction, including the ratio of MNPs to enzyme, GA concentration,crosslinking time and immobilization time. Moreover, under the optimal conditions, pH tolerance,thermo stability and reusability of the immobilized enzyme were investigated and compared with the free one. In order to evaluate the change of the affinity of the enzyme to its specific substrate after immobilization, the Michaelis-Menten constant(K_m) was also studied. Finally, the immobilized α-glucosidase combining with high performance liquid chromatography-tandem mass spectrometry technique(HPLC-MS/MS) was applied to screen and identify eight inhibitors from Polygonum cuspidatum extract. These results indicated that the established method had the broad prospects for biotechnological applications.

Effects of the ambient fine particulate matter(PM2.5) exposure on urinary metabolic profiles in rats using UPLC-Q-TOF-MS

In order to study the damage of ambient fine particulate matter(PM2.5) to organism in the environment,the method of urinary metabolomics was used to detect the potential endogenous metabolites and their related metabolic pathways to clarify the toxicity mechanisms. Particles of PM2.5 collected from the fibrous membrane were extracted ultrasonically and dissolved in physiological saline to prepare PM2.5 suspension. The solution of saline and fine particular matter was injected into the trachea of rats respectively. The rats were injected two times a week for four weeks. Samples of 24-h urine were collected at the 14 th day after the end of exposure, and the ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry(UPLC-Q-TOF-MS) was used for the metabolomics detection. Principal component analysis(PCA) was used to investigate the global metabolomic alterations and a clear separation in the scatter diagram were observed. 17 potential endogenous metablites were identified from urinary samples in rats by UPLC-Q-TOF-MS. The primary metabolism pathways involved pentose and glucuronate interconversions, starch and sucrose metabolism, tryptophan metabolism, tyrosine metabolism, phenylalanine metabolism, purine metabolism, acetaminophen metabolism pathway, retinol metabolism and valproic acid metabolism pathway.The results are helpful to understand the toxicological mechanisms of PM2.5 and screened out potential biomarkers of rats which exposure to PM2.5.