Polysaccharide extracts of Astragalus membranaceus and Atractylodes macrocephala promote intestinal epithelial cell migration by activating the polyamine-mediated K+ channel.

Astragalus membranaceus (Radix Astragali, RA) and Atractylodes macrocephala (Rhizoma Atractylodis Macrocephalae, RAM) are often used to treat gastrointestinal diseases. In the present study, we determined the effects of polysaccharides extracts from these two herbs on IEC-6 cell migration and explored the potential underlying mechanisms. A migration model with IEC-6 cells was induced using a single-edged razor blade along the diameter of cell layers in six-well polystyrene plates. The cells were grown in control media or media containing spermidine (5 µmol·L-1, SPD), alpha-difluoromethylornithine (2.5 mmol·L-1, DFMO), 4-Aminopyridine (40 µmol·L-1, 4-AP), the polysaccharide extracts of RA or RAM (50, 100, or 200 mg·L-1), DFMO plus SPD, or DFMO plus polysaccharide extracts of RA or RAM for 12 or 24 h. Next, cytosolic free Ca2+ ([Ca2+]cyt) was measured using laser confocal microscopy, and cellular polyamine content was quantified with HPLC. Kv1.1 mRNA expression was assessed using RT-qPCR and Kv1.1 and RhoA protein expressions were measured with Western blotting analysis. A cell migration assay was carried out using Image-Pro Plus software. In addition, GC-MS was introduced to analyze the monosaccharide composition of both polysaccharide extracts. The resutls showed that treatment with polysaccharide extracts of RA or RAM significantly increased cellular polyamine content, elevated [Ca2+]cyt and accelerated migration of IEC-6 cells, compared with the controls (P < 0.01). Polysaccharide extracts not only reversed the inhibitory effects of DFMO on cellular polyamine content and [Ca2+]cyt, but also restored IEC-6 cell migration to control level (P < 0.01 or < 0.05). Kv1.1 mRNA and protein expressions were increased (P < 0.05) after polysaccharide extract treatment in polyamine-deficient IEC-6 cells and RhoA protein expression was increased. Molar ratios of D-ribose, D-arabinose, L-rhamnose, D-mannose, D-glucose, and D-galactose was 1.0 : 14.1 : 0.3 : 19.9 : 181.3 : 6.3 in RA and 1.0 : 4.3 : 0.1 : 5.7 : 2.8 : 2.2 in RAM. In conclusion, treatment with RA and RAM polysaccharide extracts stimulated migration of intestinal epithelial cells via a polyamine-Kv1.1 channel activated signaling pathway, which facilitated intestinal injury healing.

Diversity-Oriented Synthesis of Steviol Glycosides.

With cheap and easily available mixtures of steviol glycosides as starting materials, a practical method for steviol acquisition has been developed, on the basis of which a facile, diversity-oriented, and economic protocol for the synthesis of structurally defined steviol glycosides was established. The novel approach is featured by the highly efficient glycosylation of sterically hindered and acid-sensitive steviol via orchestrated application of Yu glycosylation, Schmidt glycosylation, and PTC glycosylation. Hence, these high-intensity sweeteners and potential lead compounds for drug development are now readily accessible.

Highly efficient synthesis of bioactive oleanane-type saponins.

Leveraging on Schmidt glycosylation method, a highly efficient approach to obtain oleanane-type triterpene saponins was fixed, whereby oleanyl mono-, disaccharide (guaianin N), trisaccharide (elatoside E), as well as tetrasaccharide (elatoside F) were obtained efficiently. The synthetic investigation has resulted in the discovery of the effect of branch-sugar incorporation sequence on the overall synthetic efficiency. Moreover, through bioactivity investigation, the cytotoxic activity of the obtained triterpenoid saponins was evaluated, and the preliminary structure-activity relationship was deduced.

o-(p-Methoxyphenylethynyl)phenyl Glycosides: Versatile New Glycosylation Donors for the Highly Efficient Construction of Glycosidic Linkages.

A novel alkyne-activation-based glycosylation protocol using o-(p-methoxyphenylethynyl)phenyl (MPEP) glycoside was established. The glycosyl MPEP donors were shelf-stable and could be prepared efficiently via Sonogashira reaction from the corresponding o-iodophenyl (IP) glycosides. The outstanding stability of IP glycosides as well as their efficient transformations to MPEP glycosides dramatically facilitates the syntheses of MPEP glycosyl donors and IP glycosyl acceptors. Furthermore, they make the MPEP glycosylation protocol applicable to the latent-active oligosaccharide and glycoconjugate synthetic strategy, with IP glycosides as the latent form and MPEP glycosides as the active form, as illustrated by the highly efficient fabrication of Streptococcus pneumoniae type 3 trisaccharide. The phenolic glycoside nature of MPEP glycosides bestows on the new glycosyl donors enhanced stability compared to their thioglycoside counterparts toward activation conditions applied for glycosyl trichloroacetimidate (TCAI) and o-alkynylbenzoate (ABz) donor. Thus, MPEPs can also be utilized in the selective one-pot glycosylation strategy, as exemplified by the syntheses of oligosaccharides via successive glycosylations with glycosyl TCAI, ABz, and EPMP as donors. Despite sharing identical promotion conditions with thioglycoside donors, the odor-free starting material (IP), the stable departure structure of the leaving group (3-iodobenzofuran), and the decreased nucleophilicity of the o-MPEP glycoside help to eliminate the three major shortcomings of the thioglycoside donors (unpleasant odor of starting material, detrimental interference of the cleaved leaving group, and aglycon intra- or intermolecular migration) while maintaining the prominent features of the thioglycoside methodology, including the broad substrate scopes, the mild promotion conditions, the stability of glycosyl donors, and the versatile applications in existing glycoside synthesis strategies. Based on the experimental results, a mechanism for MPEP activation was proposed, which was supported by systematic mechanistic investigations, including trapping of active intermediates, design of a vital disarmed rhamnosyl donor, and isolation and characterization of the departure species of the leaving group.

Theoretical Designs for Organoaluminum C2Al4R4 with Well-Separated Al(I) and Al(III).

It is well-known that the chemistry of aluminum is dominated by Al(III) in the +3 oxidation state. Only during the past 2 decades has the chemistry of Al(I) and Al(II) been rapidly developed. However, if Al(I) and Al(III) are combined, the inherently high reactivities of Al(I) and Al(III) mostly result in their coupling with each other or interacting with surrounding elements, which easily results in significant deactivation or quenching of the desired oxidation states, as in the case of reported mixed valent Al-compounds. In this article, we report an unprecedented type of organoaluminum system, C2Al4R4 (R = H, SiH3, Si(C6H5)3, SiiPrDis2, SiMe(SitBu3)2), whose lowest-energy structure, C2Al4R4-01, contains two Al(I) and two Al(III) atoms. The global nature and bonding motif of the parent C2Al4R4-01 (R = H) were supported by an extensive global isomeric search, CBS-QB3 energy calculations, adaptive natural density partitioning, and bond order analysis. Interestingly and in sharp contrast to most organoaluminum species, C2Al4R4-01 is associated with little multicenter bonding. C2Al4R4-01 has a high feasibility of being observed either in the gas or condensed phases (with suitable substitutents). With well-separated Al(I) and Al(III), C2Al4R4-01 (with suitable substitutents) could serve as the first Al/Al frustrated Lewis pair.

A template for a planar tetracoordinate heavier group 14 atom: a global study of C2Si2X(q) (X = C, Si, Ge, Sn, Pb; q = +1, 0, -1).

Through a global isomeric study, we computationally identified the first structural template C2Si2X that could encompass a planar tetracoordinate X for all the heavier group 14 elements X in the 0, +1 or -1 charge state. We thus significantly expanded the traditional 16/17/18ve rules to 19/20/21ve for ptX.

How can carbon favor planar multi-coordination in boron-based clusters? Global structures of CB(x)E(y)(2-) (E = Al, Ga, x + y = 4).

With the high preference in forming multi-center bonding, boron has been a miracle ligand in constructing diverse planar multi-coordinate (pM) (tetra/hyper) species. Unfortunately, the boron ligand usually dislikes encompassing a pM carbon (pMC) due to the high competition with pM boron (pMB), which makes the realization of boron-based pMC very difficult and quite challenging. Herein, we propose a strategy that by means of cooperative doping and charge-compensation, we can successfully improve and tune the stability of pMC relative to pMB for CB4(2-). In the free CBxEy(2-) (E = Al/Ga) species, ptC is thermodynamically less stable than the global ptB in mono- and di-substituted systems, in agreement with the results of Boldyrev and Wang. However, the thermodynamic preference of pMC increases along with the Al/Ga-doping. The pMC species can be further stabilized by the introduction of the alkaline-earth counterion (Mg(2+)). CB2E2Mg (E = Al, Ga) designed in the present study represents the first successful design of a boron-based planar penta-coordinate carbon (ppC) structures as the global minima. The strategy proposed in this study should be useful in the manipulation of competition between exotic pMC and pMB in B-based systems.

[Effect of polysaccharides from Radix Glycyrrhizae on migration and polyamines contents of IEC-6 cell].

OBJECTIVE: To study the effect of polysaccharides from Radix Glycyrrhizae on migration and polyamines (putrescine, spermidine and spermine) contents of IEC-6 cell. METHODS: Cell migration model was induced by scratch method in each well,and the polyamines in IEC-6 cell was determined by pre-column derivation high performance liquid chromatography. The polysaccharides inhibited effect on migration and polyamines contents of IEC-6 cells, and on IEC-6 cell migration by DFMO (a polyamines synthesis inhibitor) and the polyamines contents in the cells were observed. RESULTS: The polysaccharides (50 mg/L or 100 mg/L) was able to promote the cell migration, reverse the cell migration inhibition by DFMO, enhance the IEC-6 cell polyamines (putrescine, spermidine and spermine) contents in the process of cell migration and reverse the reduction of polyamines (putrescine, spermidine and spermine) induced by DFMO. CONCLUSION: The effect of Radix Glycyrrhizae on the gastrointestinal mucosal damage repairing may be related to increasing polyamine content in cells and promoting cell migration.