Intestinal mucositis is a clinically related adverse reaction of antitumor treatment. Majority of patients receiving high-dose chemical therapy, radiotherapy, and bone-marrow transplant suffer from intestinal mucositis. Clinical manifestations of intestinal mucositis mainly include pain, body-weight reduction, inflammatory symptom, diarrhea, hemoproctia, and infection, which all affect regular nutritional input and enteric function. Intestinal mucositis often influences adherence to antitumor treatment because it frequently restricts the sufferer’s capacity to tolerate treatment, thus resulting in schedule delay, interruption, or premature suspension. In certain circumstances, partial and general secondary infections are found, increasing the expenditures on medical care and hospitalization. Current methods of treating intestinal mucositis are provided, which do not always counteract this disorder. Against this background, novel therapeutical measures are extremely required to prevent and treat intestinal mucositis. Plant-derived natural compounds have lately become potential candidates against enteric injury ascribed to the capacity to facilitate mucosal healing and anti-inflammatory effects. These roles are associated with the improvement of intestinal mucosal barrier, suppression of inflammatory response and oxidant stress, and modulation of gut microflora and immune system. The present article aims at systematically discussing the recent progress of plant-derived natural compounds as promising treatments for intestinal mucositis.
The structures of histidine intercalated hydrotalcite–montmorillonite complex (His–LDHs–MMT) were studied using the DMol3 code, GGA/PW91 function, and DND basis set of the density functional theory (DFT). The geometries of His–LDHs–MMT were optimized, and their electronic properties were calculated. The results showed that the structure of the complex can be seen as that the quaternary ammonium group of histidine was adsorbed on the oxygen of MMT lamella, and its oxygen on the carboxylic acid anion was combined with the hydrogen atoms of the LDHs lamella. It was determined that the interaction mainly consisted in hydrogen bonding and electrostatic force. The average binding energies per histidine of His–LDHs and His–MMT were about −65.89 and −78.44 kcal/mol, respectively. The density of states of the complexes showed that the 2p orbitals of oxygen were dominant, and the 1s orbit of hydrogen near the Fermi level indicate the formation of hydrogen bonds in the complex. The charge density data displayed the density field of histidine carboxylic acid anion overlapped with that of hydrotalcite layer, indicating that a strong hydrogen bond interaction existed between histidine and hydrotalcite layer. The analysis of the electrostatic potential of complex indicated that the electrostatic interaction between histidine and MMT is obviously stronger than that of LDHs. The simulated XRD spectra showed the special diffraction peaks of LDHs and MMT layer in the complex.
The conception of point group of molecules is one of the core contents in chapter of molecular symmetry of structural chemistry course.It is also one of the basic theories to understand the strucutral symmetry of molecules and the relationship between their structures and molecular properties.Therefore, it is of importance to master the identification method of point group of molecules based on their symmetric elements in structures.This paper compared the identification processes of point group of molecules in different structural chemistry textbooks, discussed potential imperfections of classic identification process of point group of molecules, and proposed a modified identification process of point group of molecules, which could help undergradute and graduate students to know and understand the intention of point group of molecules.
After oxidizing organic nitrogenous and inorganic nitrogenous to nitrate by potassium sulfate, the detection method of total ammonia in brine by ultraviolet-visible spectrophotometry was introduced. The recycle rate are 98.6%~107.5% when the concentration of standards samples was over 0.7 mg/L. the relative standards deviation was 3.52%. The lowest quantitation limit of 10 mL was 0.1 mg/L. The operation of method was simple, and took short time. The requirements of anslysi and detection were met with better standard curve linearity, accuracy and precision.
Allylic alcohols, as common and readily available building blocks, could be converted into many widely used carbonyl compounds through isomerization reactions. However, these processes often involve expensive transition metal (TM) complexes as the catalyst. What is the bottleneck in the mechanism when no TM is used? In this study, density functional theory (DFT) was employed to explore the mechanistic patterns of allylic alcohols catalyzed using bases, such as KOH, NaOH, LiOH, tBuOK, tBuONa, tBuOLi, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,3,4,6,7,8-hexahydro-1-methyl-2H-pyrimido[1,2-a]pyrimidine, and 1,8-diazabicyclo[5.4.0]undec-7-ene. Our results show that bases containing metal cations follow the metal cation-assisted (MCA) mechanism, whereas organic bases without metal cations follow the ion pair-assisted (IPA) mechanism. The catalytic efficiency of bases containing metal cations is higher than that of bases without metal cations, indicating that metal cations play an important role in the reaction. Additionally, the modulation of substituents R1 and R2 in the substrate reveals that electron-withdrawing groups are favorable for C–H bond cleavage, and electron-donating groups are favorable for hydrogen transfer. To better understand these patterns, we applied the DFT and information-theoretic approach (ITA) to examine the impact of bases and substrate substituents on the reactivity of allylic alcohol isomerization. This work should provide a much-needed theoretical guidance to design better non-TM catalysts for the isomerization of allylic alcohols and their derivatives.
For catalytic processes involving multiple reaction pathways such as the ethanol steam reforming (ESR), tailoring the active site structure of catalysts to achieve the desired catalytic selectivity is of vital importance and remains a challenge. Here, we report a heterogeneous Ru–Ni catalyst by anchoring Ru clusters onto the defect sites of Ni nanoparticles. The resulting strained Ru–Ni interface shows a high activity toward the C–C bond cleavage that is essentially required for hydrogen production via ESR. The C–O bond rupture in the side reaction (methanation) is significantly inhibited. This results in an extremely high H2 yield of 4.2 molH2/molEtOH at 350 °C, superior to the previously reported ESR catalysts working at medium-low temperature (300–500 °C). An experimental-computational combination study verifies that the conversion of Ni surface defects to the Ru–Ni interface plays a decisive role in the remarkably improved H2 yield. This work demonstrates an effective strategy to largely enhance the bond-breaking selectivity via tuning the active site structure at the catalyst surface/interface.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
