RESUMO

Abstract Gut bacterial β-glucuronidase (GUS) can reactivate xenobiotics that exert enterohepatic circulation- triggered gastrointestinal tract toxicity. GUS inhibitors can alleviate drug-induced enteropathy and improve treatment outcomes. We evaluated the inhibitory effect of Polygonum cuspidatum Siebold & Zucc. and its major constituents against Escherichia coli GUS (EcGUS), and characterized the inhibitory mechanism of each of the components. Trans-resveratrol 4'-O-β-D-glucopyranoside (HZ-1) and (-)-epicatechin gallate (HZ-2) isolated from P. cuspidatum were identified as the key components and potent inhibitors. These two components displayed strong to moderate inhibitory effects on EcGUS, with Ki values of 9.95 and 1.95 μM, respectively. Results from molecular docking indicated that HZ-1 and HZ-2 could interact with the key residues Asp163, Ser360, Ile 363, Glu413, Glu504, and Lys 568 of EcGUS via hydrogen bonding. Our findings demonstrate the inhibitory effect of P. cuspidatum and its two components on EcGUS, which supported the further evaluation and development of P. cuspidatum and its two active components as novel candidates for alleviating drug-induced damage in the mammalian gut.

RESUMO

Hazardous heavy metals in Municipal Solid Waste Incineration (MSWI) fly ash are a threat to the environment and ecosystems. The objective of the work is to investigate the solidification of MSWI fly ash and the immobilization of the heavy metals through alkaline activation reaction with waste glass as an additive. Compressive strength measurement, X-ray diffraction (XRD), 29Si nuclear magnetic resonance spectroscopy (29Si NMR) and scanning electron microscope (SEM) were performed to evaluate the solidification effect and characterize the microstructure of alkali-activated MSWI fly ash-based mortars. The leaching test, back-scattered electron microscopy (BSE) and X-ray photoelectron spectroscopy (XPS) were conducted to determine the heavy metals' immobilization effect and their immobilization forms. It was found that waste glass addition effectively reinforced the solidification of MSWI fly ash and immobilized the heavy metals. With 40% addition of waste glass, the compressive strength reached a maximum of 3.55 MPa. The immobilization efficiency of Cr increased with the addition of waste glass, while that of Cu, Pb, Zn and Cd is dependent on the eluant final pH, which decreased with the decrease of eluant final pH. The main immobilization forms include physical encapsulation, the formation of alkaline environment and the generation of silicate compounds.

Assuntos

RESUMO

This study sought to analyze the effect of curing temperature on mechanical strength and microstructure of a copper tailing-based geopolymer via scanning electron microscopy (SEM), HCl extraction, nuclear magnetic resonance (NMR), and X-ray diffraction (XRD). The distribution of gel formed in geopolymers tended to be uniform with increasing curing temperature from 25 to 80 °C. Moreover, the percentage of Si sites in C-S-H and N-A-S-H gels increased from 62.08% to 78.94% and more tetrahedral [AlO4] was incorporated into the tetrahedron [SiO4] backbone, leading to an increase of compressive strength from 10.2 to 39.6 MPa. When the curing temperature was increased to 120 °C, the percentage of Si sites in C-S-H and N-A-S-H gel decreased to 69.52%, and the compressive strength decreased to 27.5 MPa. Moderately elevated curing temperature promoted the dissolution of aluminosilicate while curing temperatures above 80 °C hindered it. Excessive curing temperature led to a decrease in the geopolymer alkaline medium.

Assuntos

RESUMO

Alkaline activation is of great potential in the solidification of municipal solid waste incineration (MSWI) fly ash, but the metallic aluminum in the ash inhibits its application. This work studies the effects of residual metallic aluminum on the expansion and microstructure of alkali-activated MSWI fly ash-based pastes. Based on the results obtained, an optimized preparation process is suggested. Characterizations of the pastes include expansion ratio, morphology (SEM), mechanical strength and microstructure (XRD and FTIR). It is confirmed that MSWI fly ash could be solidified through alkaline activation when using a small amount of coal fly ash to adjust the reactive silica and aluminum ratios. In the optimized preparation, sodium hydroxide was added separately, so that expansion in the pastes was significantly mitigated, the formation of geopolymer gel was improved and the compressive strength of the pastes increased.

Assuntos