Preparation and Characterization of Urushiol Methylene Acetal Derivatives with Various Degrees of Unsaturation in Alkyl Side Chain

Preparation of urushiol derivatives was carried out in response to the drug industry’s increasing demand for new synthetic anticancer agents. Urushiol methylene acetal derivatives were synthesized in high yields by reaction of urushiol with methylene chloride under the catalytic action of NaOH. Four kinds of urushiol methylene acetal monomers were separated by silica-gel column and preparative HPLC, and their structures were elucidated by extensive spectroscopic methods, including 1D-NMR and 2D-NMR (1H, 13C-NMR, 1H-1HCOSY, HSQC, and HMBC) as well as TOF-MS. They were identified as 3-[pentadecyl] benzene methylene ether (compound 1), 3-[8′-pentadecatrienyl] benzene methylene ether (compound 2), 3-[8′,11′-pentadecatrienyl] benzene methylene ether (compound 3), and 3-[8′,11′,14′-pentadecatrienyl] benzene methylene ether (compound 4). This research provides a theoretical reference for exploration of these interesting and potentially bioactive compounds

Single-atom tailoring of platinum nanocatalysts for high-performance multifunctional electrocatalysis

Platinum-based nanocatalysts play a crucial role in various electrocatalytic systems that are important for renewable, clean energy conversion, storage and utilization. However, the scarcity and high cost of Pt seriously limit the practical application of these catalysts. Decorating Pt catalysts with other transition metals offers an effective pathway to tailor their catalytic properties, but often at the sacrifice of the electrochemical active surface area (ECSA). Here we report a single-atom tailoring strategy to boost the activity of Pt nanocatalysts with minimal loss in surface active sites. By starting with PtNi alloy nanowires and using a partial electrochemical dealloying approach, we create single-nickel-atom-modified Pt nanowires with an optimum combination of specific activity and ECSA for the hydrogen evolution, methanol oxidation and ethanol oxidation reactions. The single-atom tailoring approach offers an effective strategy to optimize the activity of surface Pt atoms and enhance the mass activity for diverse reactions, opening a general pathway to the design of highly efficient and durable precious metal-based catalysts

Single-atom tailoring of platinum nanocatalysts for high-performance multifunctional electrocatalysis

Platinum-based nanocatalysts play a crucial role in various electrocatalytic systems that are important for renewable, clean energy conversion, storage and utilization. However, the scarcity and high cost of Pt seriously limit the practical application of these catalysts. Decorating Pt catalysts with other transition metals offers an effective pathway to tailor their catalytic properties, but often at the sacrifice of the electrochemical active surface area (ECSA). Here we report a single-atom tailoring strategy to boost the activity of Pt nanocatalysts with minimal loss in surface active sites. By starting with PtNi alloy nanowires and using a partial electrochemical dealloying approach, we create single-nickel-atom-modified Pt nanowires with an optimum combination of specific activity and ECSA for the hydrogen evolution, methanol oxidation and ethanol oxidation reactions. The single-atom tailoring approach offers an effective strategy to optimize the activity of surface Pt atoms and enhance the mass activity for diverse reactions, opening a general pathway to the design of highly efficient and durable precious metal-based catalysts

Thermal stability and thermal decomposition kinetics of Ginkgo biloba leaves waste residue

Non-isothermal thermogravimetric (TG) analysis was used to investigate the thermal stability and kinetics of three types of Ginkgo biloba leaves. These three types of Ginkgo biloba leaves included: Ginkgo biloba leaves before enzymolysis and ultrasound extraction (G1), Ginkgo biloba leaves after enzymolysis and ultrasound extraction (G2), and Ginkgo biloba leaves after soxhlet extraction (G3). Thermogravimetric/dynamic thermogravimetric, (dynamic TG) experiments indicated that the thermal stability of G2 and G3 were weaker than G1. Kissinger, Flynn-Wall-Ozawa, Friedman, and Coats-Redfern methods were firstly utilized to calculate the kinetic parameters and predicted decomposition mechanism of G1, G2, and G3. The thermal decomposition of G1, G2, and G3 were all corresponded to random nucleation and growth, following the Avrami-Erofeev equation, and activation energy of which were 191.4, 149.9, and 201.6 kJ/moL, respectively. In addition, the thermal decomposition G1, G2, and G3 were endothermic, irreversible and non-spontaneous

Isolation of Sulfuretin and Butin from Rhus verniciflua Stokes Using Medium-pressure Liquid Chromatography and their Tyrosinase Inhibitory Effects

The aim of this study was to separate antityrosinase compounds of the ethyl acetate fraction from Rhus verniciflua Stokes using medium pressure liquid chromatography. Among the different fractions, the Fr.6 fraction showed the highest antityrosinase capacity (96.5%), followed by the Fr.5 fraction (85.6%). The Fr.1 fraction showed the lowest antityrosinase capacity (12.4%). Bioactivity-guided fractionation of Fr.5.5 and Fr.6.4 led to the isolation and identification of butin and sulfuretin. Then the inhibitory effects of butin and sulfuretin on the monophenolase and diphenolase activity of mushroom tyrosinase were investigated. The results showed that butin and sulfuretin can act as potent inhibitors of monophenolase and diphenolase activities of the enzyme, and the IC50 of the butin and sulfuretin were 16.0 μmol/L and 13.64 μmol/L, respectively. The lag period of the enzyme was obviously lengthened; it was estimated to be 1 min in the absence of inhibitor, extended to 26 min in the presence of 185 μmol/L of butin, and 6 min in the presence of 111.1 μmol/L of sulfuretin. A kinetic analysis showed that butin and sulfuretin are competitive inhibitors. The results revealed that the butin and sulfuretin took up the loci of the substrate combined with enzyme, or blocked the anionic initiation by eliminating free radicals, thus weakening the catalytic reaction of oxidation of L-dopa

Polyprenols of Ginkgo biloba Enhance Antibacterial Activity of Five Classes of Antibiotics

Polyprenol (GBP) from Ginkgo biloba Leaves (GBL) is an important lipid with many bioactive effects. The effect of GBP on antibacterial properties of five antibiotics belonging to different classes was through analysis of inhibition halos, MIC, and FIC index. And we studied the time-killing curves and Ca2+ mobilization assay in Staphylococcus aureus cells treated with GBP microemulsion and gentamicin sulfate under MIC/2 conditions. These results showed that the GBP microemulsion (average diameter 90.2 nm) combining with gentamicin sulfate had the highest enhancing antibacterial effect against Staphylococcus aureus, and the MIC value was 33.0 μg/mL. The increase of the antibacterial effect of tested antibiotics was positively correlated with the decrease of the average diameter of GBP microemulsion. Moreover, GBP microemulsion enhanced antibacterial effect and prolonged antibacterial time of GBP combining with gentamicin sulfate against Staphylococcus aureus. GBP microemulsion could enhance the ability of gentamicin inducing an increase in intracellular calcium concentrations to Staphylococcus aureus. GBP microemulsion could help some classes of antibiotics to inhibit or kill bacteria. This study supports the fact that GBP microemulsion obviously can not only reduce the dosage of some classes of antibiotics, but also reduce the frequency of the antibiotic use in vitro

Preparation of polyprenol/poly (β-amino ester)/galactose targeted micelle carrier for enhancing cancer therapy

Lacking of substantial physiological activity and low utilization remains a problem for most conventional drug carriers. Polyprenol with beneficial medical effects and high availability could be an ideal candidate for solving this issue. Here, Ginkgo biloba leaves polyprenol (GBP)-based derivative was prepared by Michael addition reaction of poly (β-amino esters) (PBAE) with GBP and galactose (Gal). The intervention of poly (β-amino ester) and galactose promoted GBP-PBAE-Gal to depict as micellar carrier, enhancing the loading of hydrophobic DOX and the sensitivity to the specific tumor microenvironment, with the largest DOX loading of 28.62 ± 1.49 % and the efficient DOX release rate of 90.30 %. In the meantime, GBP-PBAE-Gal exhibited enhanced colloidal stability at 640-folds of dilution and in the presence of serum and realized the possibility of long-term storage at room temperature. Additionally, GBP-PBAE-Gal was safe for human red blood cells and human normal liver cells HL-7702. When applied for DOX delivery to HepG2 cells, GBP-PBAE-Gal increased the targeting of DOX to intensify its inhibition on HepG2 cells. Compared to free DOX, the DOX loaded into GBP-PBAE-Gal presented stronger anticancer activity, with IC50 of 0.56 μg/mL at 72 h. Besides, the anticancer mechanism study revealed that GBP-PBAE-Gal arrested the cell cycle in HepG2 cells, suggesting the potential of GBP-based carrier for intensive treatment. This research evidenced the feasibility and high availability of the GBP to use as a drug carrier, providing a novel candidate for drug delivery systems