Plasma-Induced Selective Propylene Epoxidation Using Water as the Oxygen Source

Propylene oxide (PO) is a critical gateway chemical used in large-scale production of plastics and many other compounds. In addition, PO is also used in many smaller-scale applications that require lower PO concentrations and volumes. These include its usage as a fumigant and disinfectant for food, a sterilizer for medical equipment, as well as in producing modified food such as starch and alginate. While PO is currently mostly produced in a large-scale propylene epoxidation chemical process, due to its toxic nature and high transport and storage costs, there is a strong incentive to develop PO production strategies that are well-suited for smaller-scale on-site applications. In this contribution, we designed a plasma–liquid interaction (PLI) catalytic process that uses only water and C3H6 as reactants to form PO. We show that hydrogen peroxide (H2O2) generated in the interactions of water with plasma serves as a critical oxidizing agent that can epoxidize C3H6 over a titanium silicate-1 (TS-1) catalyst dispersed in a water solution with a carbon-based selectivity of more than 98%. As the activity of this plasma C3H6 epoxidation system is limited by the rate of H2O2 production, strategies to improve H2O2 production were also investigated

Enabling Solar Water Oxidation by BiVO₄ Photoanodes in Basic Media

Titanium dioxide (TiO₂) deposited by atomic layer deposition (ALD) has been the most commonly used protection layer to enhance chemical and photoelectrochemical stabilities of photoelectrodes. In this study, we report a new electrochemical deposition method that can place a thin, conformal TiO₂ coating layer on a photoelectrode. This method takes <1 min and may serve as a practical alternative to ALD for the deposition of a TiO₂ layer. The uniform quality of the TiO₂ protection layer was confirmed by demonstrating the chemical stability of the BiVO₄/TiO₂ electrode in strongly basic media (pH 12 and 13) where BiVO₄ readily dissolves. More importantly, the high-quality TiO₂ protection layer made it possible to comparatively investigate photoelectrochemical properties and stabilities of the BiVO₄ and BiVO₄/TiO₂ electrodes, which was critical to elucidate the effect that the chemical instability of BiVO₄ in basic media has on the rate of photocorrosion. Systematic photoelectrochemical studies for sulfite oxidation and water oxidation provided a coherent understanding of how the interplay among the relative rates of interfacial charge transfer, surface recombination, and photocorrosion affects the photocurrent generation and photostability of BiVO₄. On the basis of this understanding, stable photocurrent generation for water oxidation could be achieved at pH 12 over 20 h using a BiVO₄/TiO₂/FeOOH/NiOOH electrode where FeOOH/NiOOH served as oxygen evolution catalyst. The results and discussion contained in this study provide new insights into the understanding of photocurrent decay caused by photocorrosion involving dissolution, enabling the development of effective strategies to achieve stable photocurrent generation

Electrochemical Synthesis of Highly Oriented, Transparent, and Pinhole-Free ZnO and Al-Doped ZnO Films and Their Use in Heterojunction Solar Cells

Electrochemical synthesis conditions using nonaqueous solutions were developed to prepare highly transparent (<i>T</i> > 90%) and crystalline ZnO and Al-doped ZnO (AZO) films for use in solar energy conversion devices. A focused effort was made to produce pinhole-free films in a reproducible manner by identifying a key condition to prevent the formation of cracks during deposition. The polycrystalline domains in the resulting films had a uniform orientation (i.e., the <i>c</i>-axis perpendicular to the substrate), which enhanced the electron transport properties of the films. Furthermore, electrochemical Al doping of ZnO using nonaqueous media, which was demonstrated for the first time in this study, effectively increased the carrier density and raised the Fermi level of ZnO. These films were coupled with an electrodeposited p-type Cu₂O to construct p-n heterojunction solar cells to demonstrate the utilization of these films for solar energy conversion. The resulting n-ZnO/p-Cu₂O and n-AZO/p-Cu₂O cells showed excellent performance compared with previously reported n-ZnO/p-Cu₂O cells prepared by electrodeposition. In particular, replacing ZnO with AZO resulted in simultaneous enhancements in short circuit current and open circuit potential, and the n-AZO/p-Cu₂O cell achieved an average power conversion efficiency (η) of 0.92 ± 0.09%. The electrodeposition condition reported here will offer a practical and versatile way to produce ZnO or AZO films, which play key roles in various solar energy conversion devices, with qualities comparable to those prepared by vacuum-based techniques

Effects of Cudrania tricuspidata Fruit Extract and Its Active Compound, 5,7,3′,4′-Tetrahydroxy-6,8-diprenylisoflavone, on the High-Affinity IgE Receptor-Mediated Activation of Syk in Mast Cells

Cudrania tricuspidata fruit extract contains a rich source of prenylated flavonoids with potential antiatherosclerotic, hepatoprotective, and anti-inflammatory properties. However, the effect of <i>C. tricuspidata</i> fruit extracts and its active compounds on the high-affinity IgE receptor (FcεRI)-mediated signaling remains unknown. In the present study, the effect of methanol extract from the fruits of <i>C. tricuspidata</i> (MFC) and its active compound, 5,7,3′,4′-tetrahydroxy-6,8-diprenylisoflavone (THDPI), on FcεRI-mediated signaling in mast cells was investigated. MFC and THDPI suppressed mast cell degranulation and Ca²⁺ influx. MFC also interfered with IgE–FcεRI interaction and decreased FcεRIβ mRNA expression in mast cells. Furthermore, MFC and THDPI inhibited the phosphorylation of Syk, LAT, and PLCγ and F-actin redistribution. These results indicate that MFC and its active compound, THDPI, inhibit mast cell activation through the inhibition of FcεRI-mediated Syk activation, suggesting a therapeutic potential for controlling mast cell activation in inflammatory and/or allergic processes

Heartwood extract of <i>Rhus verniciflua</i> Stokes and its active constituent fisetin attenuate vasoconstriction through calcium-dependent mechanism in rat aorta

<p><i>Rhus verniciflua</i> Stokes (RVS) exert cardiovascular protective activity by promoting blood circulation, but its active ingredients and underlying mechanism have yet to be identified. This study investigated the vascular effects of RVS, focusing on vasoconstriction and smooth muscle Ca²⁺ signaling. RVS heartwood extract attenuated contraction of aortic rings induced by the vasoconstrictors serotonin and phenylephrine, and inhibited the Ca²⁺ signaling evoked by serotonin in vascular smooth muscle cells. Subsequent activity-guided fractionation identified fisetin as an active constituent exerting a Ca²⁺ inhibitory effect. Fisetin could inhibit major Ca²⁺ mobilization pathways including extracellular Ca²⁺ influx mediated by the L-type voltage-gated Ca²⁺ channel, Ca²⁺ release from the intracellular store and store-operated Ca²⁺ entry. In accordance with Ca²⁺ inhibitory effect, fisetin attenuated vasoconstriction by serotonin and phenylephrine. These results suggest that the anticontractile effect, which is presumably mediated by inhibition of Ca²⁺ signaling, may contribute to the improvement of blood circulation by RVS.</p> <p><i>Rhus verniciflua</i> Stokes extract and its active constituent fisetin improve blood circulation by inhibiting smooth muscle Ca²⁺ signaling and thereby attenuating vasoconstriction.</p

Neuroprotective Xanthones from the Root Bark of <i>Cudrania tricuspidata</i>

Seventeen new prenylated xanthones (<b>1</b>–<b>17</b>) were isolated from an ethyl acetate-soluble extract of root bark of <i>Cudrania tricuspidata</i> together with 17 previously identified xanthones. The structures of the new compounds were elucidated by spectroscopic methods. Six new compounds (<b>3</b>, <b>7</b>, <b>8</b>, <b>9</b>, <b>15</b>, and <b>16</b>) and six known compounds (<b>18</b>–<b>23</b>) showed neuroprotective effects against 6-hydroxydopamine-induced cell death in human neuroblastoma SH-SY5Y cells, with EC₅₀ values of 0.7–16.6 μM

Characterization of <i>Brassica napus Flavonol Synthase</i> Involved in Flavonol Biosynthesis in <i>Brassica napus</i> L.

Recently, <i>Brassica napus</i> has become a very important crop for plant oil production. Flavonols, an uncolored flavonoid subclass, have a high antioxidative effect and are known to have antiproliferative, antiangiogenic, and neuropharmacological properties. In <i>B. napus</i>, some flavonoid structural genes have been identified, such as, <i>BnF3H-1</i>, <i>BnCHS</i>, and <i>BnC4H-1</i>. However, no studies on <i>FLS</i> genes in <i>B. napus</i> have been conducted. Thus, in this study, we cloned and characterized the function of <i>BnFLS</i> gene <i>B. napus</i>. By overexpression of the <i>BnFLS</i> gene, flavonol (kaempferol and quercetin) levels were recovered in the <i>Arabidopsis</i> <i>atfls1-ko</i> mutant. In addition, we found that the higher endogenous flavonol levels of <i>BnFLS-ox in vitro</i> shoots correlated with slightly higher ROS scavenging activities. Thus, our results indicate that the <i>BnFLS</i> gene encodes for a BnFLS enzyme that can be manipulated to specifically increase flavonol accumulation in oilseed plants and other species such as <i>Arabidopsis</i>

Lanostane Triterpenes Isolated from <i>Antrodia heteromorpha</i> and Their Inhibitory Effects on RANKL-Induced Osteoclastogenesis

Two new spiro-lanostane triterpenoids, antrolactones A and B (<b>1</b> and <b>2</b>), along with polyporenic acid C (<b>3</b>), were isolated from an EtOAc-soluble extract of <i>Antrodia heteromorpha</i> culture medium, and the chemical structures of the new compounds were elucidated by application of NMR, MS, and ECD spectroscopic techniques. All isolated compounds exhibited inhibitory effects on receptor activator of nuclear factor-kappaB ligand-induced osteoclastogenesis

Discovery of Bioactive Metabolites by Acidic Stress to a Geldanamycin Producer, <i>Streptomyces samsunensis</i>

In an effort to activate silent biosynthetic gene clusters, Streptomyces samsunensis DSM42010, a producer of geldanamycin, was cultured at four different pHs (4.5, 5.4, 6.6, and 7.4). An acidic culture condition (pH 5.4) was selected for a chemical investigation since S. samsunensis showed a different metabolic profile compared to when it was cultured under other conditions. Seven new (1–7) and four known (8–11) compounds were isolated from these cultures. The structures of the isolated compounds were determined by spectroscopic techniques and chemical derivatization. Relative and absolute configurations of the new compounds (1–5) were established using JBCA, PGME method, advanced Marfey’s method, modified Mosher’s method, and comparison of observed and calculated ECD data. Interestingly, compounds 1–3 were truncated versions of geldanamycin, and compound 4 was also deduced to originate from geldanamycin. Compound 5 was composed of 3-methyltyrosine and 6-hydroxy-2,4-hexadienoic acid connected through an amide bond. Compounds 6 and 7 were dihydrogenated forms of geldanamycin with a hydroxy substitution. It is possible that culturing this strain under acidic conditions interfered to some degree with the geldanamycin polyketide synthase, leading to production of truncated versions as well as analogues of geldanamycin. Compounds 1, 8, and 9 showed significant antivirulence activity, inhibiting production of α-toxin by methicillin-resistant Staphylococcus aureus without growth attenuation and global regulatory inhibition; compounds 1, 8, and 9 may become promising α-toxin-specific antivirulence leads with less risk of resistance development

Sesquiterpenes from <i>Inula japonica</i> with Inhibitory Effects on Nitric Oxide Production in Murine Macrophage RAW 264.7 Cells

Eight new sesquiterpenes (<b>1</b>–<b>8</b>), along with seven known sesquiterpenes (<b>9</b>–<b>15</b>), were isolated from a methanol extract of the flowers of <i>Inula japonica</i>. Their structures were elucidated by a combination of 1D and 2D NMR spectroscopic and HRESIMS data. All of isolates were evaluated for their inhibitory effects on nitric oxide production in LPS-induced RAW 264.7 cells, with their IC₅₀ values ranging from 1.9 to 15.4 μM