Biotransformation of Panax ginseng extract by rat intestinal microflora: identification and quantification of metabolites using liquid chromatography-tandem mass spectrometry

Background: In general, after Panax ginseng is administered orally, intestinal microbes play a crucial role in its degradation and metabolization process. Studies on the metabolism of P. ginseng by microflora are important for obtaining a better understanding of their biological effects. Methods: In vitro biotransformation of P. ginseng extract by rat intestinal microflora was investigated at 37°C for 24 h, and the simultaneous determination of the metabolites and metabolic profile of P. ginseng saponins by rat intestinal microflora was achieved using LC–MS/MS. Results: A total of seven ginsenosides were detected in the P. ginseng extract, including ginsenosides Rg1, Re, Rf, Rb1, Rc, Rb2, and Rd. In the transformed P. ginseng samples, considerable amounts of deglycosylated metabolite compound K and Rh1 were detected. In addition, minimal amounts of deglycosylated metabolites (ginsenosides Rg2, F1, F2, Rg3, and protopanaxatriol-type ginsenosides) and untransformed ginsenosides Re, Rg1, and Rd were detected at 24 h. The results indicated that the primary metabolites are compound K and Rh1, and the protopanaxadiol-type ginsenosides were more easily metabolized than protopanaxatriol-type ginsenosides. Conclusion: This is the first report of the identification and quantification of the metabolism and metabolic profile of P. ginseng extract in rat intestinal microflora using LC–MS/MS. The current study provided new insights for studying the metabolism and active metabolites of P. ginseng

Dual Switching in Both RAFT and ROP for Generation of Asymmetric A²A¹B¹B² Type Tetrablock Quaterpolymers

In reversible addition–fragmentation chain transfer (RAFT) polymerization, monomers are divided into “more-activated” monomers (type-A¹ monomer) and “less-activated” monomers (type-A² monomer). In ring-opening polymerization (ROP), monomers are considered to fall into electrophilically polymerizable monomers (lactones and carbonates, type-B¹ monomer) and nucleophilically polymerizable monomers (lactides and carbonates, type-B² monomer). Developing a strategy to copolymerize the four kinds of monomers for formation of asymmetric A²A¹B¹B² type tetrablock quaterpolymers by one-pot sequential ROP and RAFT polymerization is a challenge. Herein, we designed and synthesized a molecule, 2-hydroxyethyl 2-(methyl­(pyridin-4-yl)­carbamo­thioylthio)­propanoate, which functioned as a trifunctional initiator, to initiate ROPs and to modulate RAFT polymerizations sequentially in one-pot. We proposed a dual “acid/base switch” strategy in both RAFT polymerizations and ROPs for one-pot generation of asymmetric A²A¹B¹B² type tetrablock quaterpolymers. A series of di-, tri-, and tetrablock copolymers were synthesized and showed predicted molar mass and narrow dispersities, manifesting that the ROPs and RAFT polymerizations proceeded independently in controlled manners. The dual “acid/base switch” strategy paved a new avenue to combine RAFT polymerizations and ROPs for synthesis of designed copolymers with advanced functionalities and architectures

Dichloroimidazolidinedione-Activated Beckmann Rearrangement of Ketoximes for Accessing Amides and Lactams

A novel protocol for the activation of the Beckmann rearrangement utilizing the readily available and economical geminal dichloroimidazolidinediones (DCIDs) on a substoichiometric scale (10 mol %) has been developed. A unique self-propagating mechanism for the substoichiometric dichloroimidazolidinedione-activated transformation was proposed and validated. The substrate scope of the developed protocol has been demonstrated by 23 examples with good to excellent yields (mostly 90–98%) in a short time (mostly 10–30 min), including a substrate for synthesizing the monomer of nylon-12 and a complicated steroidal substrate on a preparative scale. This research not only unveils for the first time the synthetic potential of substoichiometric amounts of dichloroimidazolidinediones in promoting chemical transformation but also offers yet another important illustration of the self-propagating cycle in the context of the Beckmann rearrangement activated by a structurally novel organic promoter