Investigation of the Binding Interaction of Mfsd2a with NEDD4-2 via Molecular Dynamics Simulations.

Major facilitator superfamily domain-containing 2a (Mfsd2a) is a sodium-dependent lysophosphatidylcholine cotransporter that plays an important role in maintaining the integrity of the blood-brain barrier and neurological function. Abnormal degradation of Mfsd2a often leads to dysfunction of the blood-brain barrier, while upregulation of Mfsd2a can retrieve neurological damage. It has been reported that Mfsd2a can be specifically recognized and ubiquitinated by neural precursor cell-expressed developmentally downregulated gene 4 type 2 (NEDD4-2) ubiquitin ligase and finally degraded through the proteasome pathway. However, the structural basis for the specific binding of Mfsd2a to NEDD4-2 is unclear. In this work, we combined deep learning and molecular dynamics simulations to obtain a Mfsd2a structure with high quality and a stable Mfsd2a/NEDD4-2-WW3 interaction model. Moreover, molecular mechanics generalized Born surface area (MM-GBSA) methods coupled with per-residue energy decomposition studies were carried out to analyze the key residues that dominate the binding interaction. Based on these results, we designed three peptides containing the key residues by truncating the Mfsd2a sequences. One of them was found to significantly inhibit Mfsd2a ubiquitination, which was further validated in an oxygen-glucose deprivation (OGD) model in a human microvascular endothelial cell line. This work provides some new insights into the understanding of Mfsd2a and NEDD4-2 interaction and might promote further development of drugs targeting Mfsd2a ubiquitination.

Aculebiphenyl A-B, new biphenyl derivatives from Ruscus aculeatus.

The investigation of chemical constituents from the rhizomes of Ruscus aculeatus resulted in the isolation of two new biphenyl derivatives, aculebiphenyls A and B (1-2), together with two known analogs (3-4). Their chemical structures were elucidated based on extensive spectroscopic interpretation and HR-ESI-MS analysis. Compounds 3-4 were isolated from the Ruscus genus for the first time. The isolated compounds were tested for anti-inflammatory activities and antibacterial activities. Compound 1 exhibited significant inhibitory effects on LPS-induced NO production and COX-2 with IC50 values of 10.8 µM and 0.4 µM. Compound 1 also significantly down-regulated the levels of inflammatory cytokines IL-1ß, IL-6, and TNF-α. Compound 1 showed moderate antibacterial activities.

Inhibitory Mechanism of Prenylated Flavonoids Isolated from Mulberry Leaves on α-Glucosidase by Multi-Spectroscopy and Molecular Dynamics Simulation.

Flavonoids have always been considered as the chemical basis for the hypoglycemic effect of mulberry leaves. In the course of our search for hypoglycemic effect agents from natural sources, a systematic study was launched to explore prenylated flavonoids from mulberry leaves. Herein, chemical investigation led to the isolation of 10 characteristic prenylated flavonoids, including two new compounds (1 and 3). Their structures were elucidated based on spectroscopic data. All compounds exhibited good α-glucosidase inhibitory activity in vitro, among which compound 2 had the best activity (IC50 = 2.6 µM), better than acarbose (IC50 = 19.6 µM). Additional in vivo tests have further demonstrated compound that compound 2 has a good ability to reduce postprandial blood glucose. Then, multi-spectroscopic methods and molecular simulation studies were used to study the inhibition mechanism. The results showed that compound 2 was a mixed inhibition of α-glucosidase and the binding process was spontaneous, with van der Waals forces as the main driving force, followed by hydrogen bonding and electrostatic forces. The above studies enriched the chemical basis of mulberry leaves, and the application of computational chemistry also provided a reference for future research on such structures.

Development of sertraline analogues as potential anti-ischemic stroke agents.

Ischemic stroke (IS) is harmful to human health and social development, and there is no medicine available at present. To find the hit compound for treating ischemic stroke, we screened 28 FDA approved nervous system drugs by using an in vitro OGD-induced stroke model. Notably, our in vitro and in vivo studies demonstrated that low-dose sertraline had good neuroprotective activities, while high-dose sertraline showed significant toxicity. Interestingly, the same high-dose sertraline in the control group did not exhibit any obvious toxic effect. Therefore, it is important to modify the structure of sertraline to improve the activity and reduce the toxicity. Stereoisomers of sertraline were first investigated to analyze the influence of stereochemistry on the neuroprotective activities, which showed no obvious difference. Then we evaluated the activity of our previously reported sertraline analogues and found that introducing amide or alkane groups to the amino moiety might be beneficial to enhance the activity and reduce the toxicity. Thus, 10 new analogues were designed, synthesized, and evaluated. Among them, compound OY-201 showed the best safety and neuroprotective activity in both in vitro and in vivo models. Moreover, it exhibited good blood-brain barrier (BBB) permeability, indicating its potential for the development of anti-ischemic stroke drugs.

Simplified Derivatives of Tetrandrine as Potent and Specific P-gp Inhibitors to Reverse Multidrug Resistance in Cancer Chemotherapy.

Targeted inhibition of a drug efflux transporter P-glycoprotein (P-gp) is an important strategy to reverse multidrug resistance in cancer chemotherapy. In this study, a rationally structural simplification to natural tetrandrine was performed based on molecular dynamics simulation and fragment growth, leading to an easily prepared, novel, and simplified compound OY-101 with high reversal activity and low cytotoxicity. Its excellent synergistic anti-cancer effect with vincristine (VCR) against drug-resistant cells Eca109/VCR was confirmed by reversal activity assay, flow cytometry, plate clone formation assay, and drug synergism analysis (IC50 = 9.9 nM, RF = 690). Further mechanism study confirmed that the OY-101 was a specific and efficient P-gp inhibitor. Importantly, OY-101 increased VCR sensitization in vivo without obvious toxicity. Overall, our findings may provide an alternative strategy for the design of novel specific P-gp inhibitor as an anti-tumor chemotherapy sensitizer.

Apoptotic effects of phenols from the twigs and leaves of Garcinia nujiangensis.

In order to find potential agents for treating cancer disease in naturally occurring compounds, we conducted a systematic phytochemical investigation on the endemic species of Garcinia nujiangensis. Three new biphenyl derivatives (1-3) and one new polycyclic polyprenylated benzophenone (4), together with four known benzophenone analogues (5-8), have been isolated from the CH2Cl2 extract of the twigs and leaves of G. nujiangensis. Their structures were determined by detailed spectroscopic analyses and comparison with structurally related known analogues. Experimental and calculated ECD method was used to determine the absolute configuration of 1 and 4. Moreover, compounds 5-7 were isolated for the first time from this species. The cytotoxicities of the new compounds were evaluated using HL-60, HepG2, and A549 human cancer cell lines. Compound 4 showed more significant antiproliferative effects against HepG2 cells with an IC50 value of 11.38 ± 0.79 µM than that of three biphenyl derivatives. The morphological features of apoptosis were evaluated in 4-treated HepG2 cells. Compound 4 effectively prevented the cell cycle progression of HepG2 cells in G2 phase. Additionally, western blot analysis indicated that treatment of 4 on HepG2 cells led to decreased expression of anti-apoptotic Bcl-2 and pro-Caspase-3, and increased protein expression of both pro-apoptotic Bax and cleaved PARP with reference to ß-actin. Overall, our results suggested that the active polycyclic polyprenylated benzophenone derivatives in the twigs and leaves of G. nujiangensis can be used as a valuable source of bioactive compounds for the pharmaceutical industry.

Two new prenylated coumarins from roots of Zanthoxylum nitidum.

Two new prenylated coumarins, 3'-hydroxytoddanone (1), and isotoddalolactone (2), along with four known analogues (3-6) were isolated from the roots of Zanthoxylum nitidum. Their chemical structures were elucidated based on extensive spectroscopic interpretation and HR-ESI-MS analysis. The absolute configuration of compound 2 was determined by comparing experimental ECD spectrum with that calculated by the time-dependent density functional theory (TDDFT) method. Compounds 4-6 were isolated from the Zanthoxylum genus for the first time. The two new compounds were tested for antiproliferative activities in vitro on the HL-60, K562 and THP-1 cell lines. Compounds 1 and 2 exhibited moderate cell growth inhibitory activities in vitro against human leukemic HL-60 cell lines, with IC50 values of 32.64 and 33.15 µM, respectively.

Prenylated isoflavones from the roots of Flemingia philippinensis as potential inhibitors of ß-amyloid aggregation.

In our efforts to find potential agents for the treatment of Alzheimer's disease in naturally occurring compounds, a systematic investigation for the active constituents of Flemingia philippinensis was carried out. Four new prenylated isoflavones, philippinone A-D (1-4), together with six known analogues (5-10), were obtained from the roots of Flemingia philippinensis. Their structures were established through extensive physical and spectroscopic data analysis. All the isolates were evaluated for their inhibitory effect of self-induced Aß aggregation among which compound 5 showed significant Aß aggregation inhibitory ability with the inhibitory rate of 70.56%. The results of molecular docking experiment for compounds 1 and 6 corresponded to that of the thioflavin-T assay. Moreover, the results further clarified the effects of different substituent group of tested compounds on the Aß aggregation inhibition. A preliminary structure-activity relationship is further discussed. Our results suggested that the isoflavonoids may mitigate the progression of AD and compounds 2 and 5 may be a candidate in the treatment of AD.

Preparation of halloysite nanotubes-encapsulated magnetic microspheres for elemental mercury removal from coal-fired flue gas.

Halloysite nanotubes (HNTs) as a natural and inexpensive clay mineral with hollow nanotubular structures, good biocompatibility and active surfaces have been ubiquitously applied in many fields. In this work, a novel multifunctional core-shell sorbent based on HNTs, CuCl2-HNTs encapsulated magnetic microspheres (SiO2@Fe3O4), was successfully fabricated and applied for Hg0 removal from flue gas with good performance for the first time. The core-shell structure prevented the composites from aggregating but kept their magnetism, which enabled the adsorbents being easily separated for reuse by an external magnetic field. In addition, the special structure also significantly enhanced the adsorption capacity of the composites by dispersing the CuCl2 modified HNTs on the prepared magnetic microspheres. The adsorption performance was comprehensively investigated and fitted by dynamic models. The adsorption followed surface adsorption, particle diffusion and chemisorption with very good SO2 tolerance. The Cu+, Cl- and lattice oxygen were the crucial components for Hg0 removal. In order to further understand the possible mechanism, an online home-made coupling system of temperature-programmed decomposition (TPD) was used to investigate the mercury species on the spent adsorbent in addition to X-ray photoelectron spectroscopy analysis. The results confirmed the mercury species adsorbed were primarily Hg0, HgO and HgCl2.

Selective Alkynylallylation of the C-C σ Bond of Cyclopropenes.

A Pd-catalyzed regio- and stereoselective alkynylallylation of a specific C-C σ bond in cyclopropenes, using allyl propiolates as both allylation and alkynylation reagents, has been achieved for the first time. By merging selective C(sp2 )-C(sp3 ) bond scission with conjunctive cross-couplings, this decarboxylative reorganization reaction features fascinating atom and step economy and provides an efficient approach to highly functionalized dienynes from readily available substrates. Without further optimization, gram-scale products can be easily obtained by such a simple, neutral, and low-cost catalytic system with high TONs. DFT calculations afford a rationale toward the formation of the products and indicate that the selective insertion of the double bond of cyclopropenes into the C-Pd bond of ambidentate Pd complex and the subsequent nonclassical ß-C elimination promoted by 1,4-palladium migration are critical for the success of the reaction.

Novel Protein Tyrosine Phosphatase 1B Inhibitor-Geranylated Flavonoid from Mulberry Leaves Ameliorates Insulin Resistance.

Mulberry leaf is a common vegetable with a variety of beneficial effects, such as hypoglycemic activity. However, the underlying mechanism of its hypoglycemic effect have not been fully revealed. In this study, two flavonoid derivatives were isolated from mulberry leaves, a new geranylated flavonoid compound (1) and its structural analogue (2). The structures of compounds 1 and 2 were elucidated using spectroscopic analysis. To study the potential hypoglycemic properties of these compounds, their regulatory effects on protein tyrosine phosphatase 1B (PTP1B) were investigated. In comparison to oleanolic acid, compounds 1 and 2 showed significant inhibitory activities (IC50 = 4.53 ± 0.31 and 10.53 ± 1.76 µM) against PTP1B, the positive control (IC50 = 7.94 ± 0.76 µM). Molecular docking predicted the binding sites of compound 1 to PTP1B. In insulin-resistance HepG2 cell, compound 1 promoted glucose consumption in a dose-dependent manner. Furthermore, western blot and polymerase chain reaction analyses indicated that compound 1 might regulate glucose consumption through the PTP1B/IRS/PI3K/AKT pathway. In conclusion, geranylated flavonoids in mulberry leaves inhibite PTP1B and increase the glucose consumption in insulin-resistant cells. These findings provide an important basis for the use of mulberry leaf flavonoids as a dietary supplement to regulate glucose metabolism.

A new xanthyletin-type coumarin from the roots of Peucedanum praeruptorum.

A new xanthyletin-type coumarin, neopeucedalactone (1), was isolated from the roots of Peucedanum praeruptorum Dunn. Its chemical structure was elucidated based on extensive spectroscopic interpretation. The absolute configurations of xanthyletin-type coumarin were determined by comparing experimental and calculated ECD spectra for the first time. Compound 1 exhibited moderate cell growth inhibitory activities in vitro against human leukemic HL-60, THP-1 cell lines, and human prostate cancer PC-3 cell lines, with IC50 values of 9.97, 27.80, and 48.68 µM, respectively. [Formula: see text].

Copper-catalysed three-component carboiodination of arynes: expeditious synthesis of o-alkynyl aryl iodides.

A copper-catalysed three-component iodoalkynylation reaction of arynes for the expeditious and versatile synthesis of o-alkynyl aryl iodides has been developed. Mechanism research shows that the reaction goes through two steps enabled by copper catalysis: the formation of 1-iodo-2-arylacetylene and the insertion of the aryne into a C(sp)-I bond.

Copper-Catalyzed Three-Component Carboamination of Arynes: Expeditious Synthesis of o-Alkynyl Anilines and o-Benzoxazolyl Anilines.

A copper-catalyzed three-component reaction of in situ formed arynes, terminal alkynes, and O-benzoylhydroxylamines has been developed. By adjusting reaction conditions, the nucleophiles in this transformation can be extended from terminal alkynes to benzoxazoles. These procedures provide a modular and facile approach to o-alkynyl anilines and o-benzoxazolyl anilines from easily available substrates in only one step.

Bioassay- and Chemistry-Guided Isolation of Scalemic Caged Prenylxanthones from the Leaves of Garcinia bracteata.

With bioassay- and chemistry-guided fractionation, seven new caged prenylxanthones including two scalemic mixtures, epiisobractatin (1), 13-hydroxyisobractatin (2), 13-hydroxyepiisobractatin (3), 8-methoxy-8,8a-dihydrobractatin (4), 8-ethoxy-8,8a-dihydrobractatin (5), garcibracteatone (6), and 8-methoxy-8,8a-dihydroneobractiatin (7), and the eight known compounds 8-15 were isolated from the leaves of Garcinia bracteata. The structures were unambiguously elucidated through analysis of spectroscopic data. The 2D structures and relative configurations of 1 and 5 were confirmed by X-ray crystallographic analysis. The separation of the enantiomers of 1-5 was accomplished by chiral-phase HPLC. The absolute configurations of the enantiomers of 1 and 5 were assigned by comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. The absolute configurations of the related compounds were determined via comparisons of their ECD data with those of the enantiomers of 1 and 5, respectively. Notably, compound 7, with a neo caged skeleton, is the first representative of a novel type of caged xanthone lacking a Δ8(8a) double bond. The isolated compounds exhibited significant cell growth inhibitory activities in vitro against human leukemic HL-60 and K562 cell lines, with GI50 values ranging from 0.2 to 8.8 µM. A preliminary structure-activity relationship is discussed.

Neobraclactones A-C, three unprecedented chaise longue-shaped xanthones from Garcinia bracteata.

Neobraclactones A-C (1-3), featuring an unprecedented further rearranged prenylxanthone skeleton with a unique octahydro-2H-1,3-dioxacyclopenta[c,d]inden-2-one scaffold, along with their biosynthesis-related known compound neobractatin (4), were isolated from the leaves of Garcinia bracteata. Their structures with absolute configurations were determined by extensive analyses of spectroscopic data and ECD calculations. Compounds 1 and 2 showed significant growth inhibition activities against the human leukaemia HL-60 and K562 cell lines with GI50 values from 0.40 to 0.86 µM.

Enantioselective [4 + 1] Annulation Reactions of α-Substituted Ammonium Ylides To Construct Spirocyclic Oxindoles.

Ammonium ylides have a long history in organic synthesis, but their application in asymmetric catalysis is still underdeveloped in regard to both substrate scope and reaction pathways compared with phosphorus and sulfur ylides. Here a previously unreported asymmetric [4 + 1] annulation reaction of 3-bromooxindoles and electron-deficient 1-azadienes has been developed through ammonium ylide catalysis of a newly designed 2'-methyl α-isocupreine (α-MeIC), efficiently delivering spirocyclic oxindole compounds incorporating a dihydropyrrole motif in excellent enantioselectivity (up to 99% ee). To the best of our knowledge, this work represents the first example of asymmetric catalysis of ammonium ylides bearing α-substitutions, and the catalytic [4 + 1] annulation pathway of ammonium ylides is also unprecedented. Moreover, (1)H NMR, mass spectroscopy, and computational calculation studies were conducted, and the catalytic cycle and a tentative explanation of the enantioselective mechanism have been successfully elucidated.

An investigation on the catalytic capacity of dolomite in transesterification and the calculation of kinetic parameters.

The catalytic capacity of dolomite in transesterification was investigated and the kinetic parameters were calculated. The activated dolomites as transesterification catalyst were characterized by X-ray diffraction, nitrogen adsorption and desorption and Hammett indicator method, where the original dolomite was analyzed by thermogravimetric and X-ray fluorescence in advance. Its potential catalytic capacity was validated from aspects of the activated temperature and the reused property, where the reliability of the experimental system was also examined. Then, influences of the catalyst added amount, the mole ratio of methanol to oil, the transesterification temperature and the transesterification time on the catalytic capacity were investigated. Finally, kinetic parameters of the transesterification catalyzed by the activated dolomite were calculated.

Xanthones from the stem bark of Garcinia bracteata with growth inhibitory effects against HL-60 cells.

Five xanthones, 1,4,5,6-tetrahydroxyxanthone (1) and bracteaxanthones III-VI (2-5) together with twenty-six known compounds (6-31), were isolated from the ethanol extract of the stem bark of Garcinia bracteata. Their structures were elucidated via spectroscopic analyses. Growth inhibitory activities of these compounds against the human leukaemic HL-60 cell line were measured in vitro. Compounds 7, 11, and 29 exhibited moderate activities with GI(50) values of 2.8, 3.4, and 3.1 µM, respectively, and a preliminary structure-activity relationship is discussed.