Hainanxylogranolides A-F: New Limonoids isolated from the seeds of Hainan mangrove plant Xylocarpus granatum.

Six new limonoids, named hainanxylogranolides A-F (1-6), together with nineteen known ones (7-25) were isolated from the seeds of a Hainan mangrove Xylocarpus granatum. The structures of the new compounds were established by extensive NMR spectroscopic data combined with the DFT and TDDFT calculated electronic circular dichroism spectra. Hainanxylogranolide A (1) is the aromatic B-ring limonoid containing a central pyridine ring and a C-17 substituted γ(21)-hydroxybutenolide moiety. Hainanxylogranolide B (2) belongs to the small group of mexicanolides containing a C3-O-C8 bridge, whereas hainanxylogranolides C and D (3 and 4) are mexicanolides comprising a C1-O-C8 bridge. Compounds 9 and 25 posed obvious inhibition effect on the tube formation of HUVECs. There are only about 25% tube-like structures were observed at the concentration of 40.0 µM of compound 25. The antiviral activities of the isolates against herpes simplex virus-1 (HSV-1) and severe fever with thrombocytopenia syndrome virus (SFTSV) were tested in vitro. Compound 23 exhibited moderate anti-SFTSV activity with the IC50 value of 29.58 ± 0.73 µM. This is the first report of anti-angiogenic effect and anti-SFTSV activity of limonoids from the genus Xylocarpus.

Ultrahigh activity of molybdenum/vanadium-doped Ni-Co phosphides nanoneedles based on ion-exchange for hydrogen evolution at large current density.

Heteroatom doping is a promising strategy to optimize the electronic structure of transition metal phosphides so enhancing the hydrogen evolution reaction (HER). However, complex and harsh experimental design is often required to achieve homogeneous doping of corresponding elements while achieving the best regulating effect. Herein, a facile ion-exchange (IE) strategy is applied to dope Mo/V species evenly into Ni-Co phosphides under mild conditions while maintaining the nanoneedle morphology. The electrochemical characterization verifies Mo dopants have a better electronic regulation effect on NiCoP crystal than V dopants, corresponding to the better hydrogen evolution performance of Mo-NiCoP/NF. Notably, due to the highly dispersed nanoneedle morphology, the synergistic effect of Ni-Co phosphides, and the optimized electronic structure, Mo-NiCoP/NF demonstrates a higher activity than that of the noble metal Pt/C at the high current density (>99 mA cm-2). The present work is supposed to open new sights for the development of high-performance catalysts by ion-exchange strategy.

Modulation engineering of in situ cathodic activation of FePx based on W-incorporation for the hydrogen evolution reaction.

In situ electrochemical activation as a new pretreating method to adjust electrocatalytic performance attracts extensive attention. However, the activation mechanisms of electrocatalysts are still ambiguous. Herein, we propose a facile modulation strategy of in situ cathodic activation of FePx based on W-incorporation (W-FePx/IF) for the hydrogen evolution reaction (HER). The activated W-FeOx with obvious surface reconstruction demonstrates the role of W-incorporation for driving the cathodic activation of FePx, which suggests the larger surface area and more active sites. In fact, W incorporation can not only accelerate the cathodic activation process but also act as the adsorption sites for Had to form the synergistic effect with FeOx for water dissociation. The obtained W-FeOx/IF exhibits greatly enhanced HER activity featuring decreased overpotential from 237.7 to 154.0 mV at 100 mA cm-2, which may be ascribed to W-FeOx with double catalytic active sites after cathodic activation. Additionally, the modulation effects of cathodic activation can be exactly achieved by changing electrochemical parameters such as CV cycles. W-FeOx/IF also shows excellent long-term stability for at least 100 h at 100 mA cm-2. This modulation engineering based on metal doping is expected to provide inspiration for the understanding of the cathodic activation process for efficient electrocatalysts.