Effects of Long-Term Storage on Radical Scavenging Properties and Phenolic Content of Kombucha from Black Tea

Kombucha is a fermented beverage. Its consumption has significantly increased during the last decades due to its perceived beneficial effects. For this reason, it has become a highly commercialized drink that is produced industrially. However, kombucha is still also a homemade beverage, and the parameters which, besides its organoleptic characteristics, define the duration of its potential beneficial properties over time, are poorly known. Therefore, this study aimed to determine the effect of 9-month storage at 4 °C with 30-day sampling on the pH, total phenolic, and flavonoid contents, free radical scavenging properties of kombucha fermented from black tea. Our results highlighted that, after four months, the phenolic content decreased significantly from the initial value of 234.1 ± 1.4 µg GAE mL⁻¹ to 202.9 ± 2.1 µg GAE mL⁻¹, as well its antioxidant capacity tested by two in vitro models, DPPH, and ABTS assays. Concomitantly, the pH value increased from 2.82 to 3.16. The novel findings of this pilot study revealed that kombucha from sugared black tea can be stored at refrigerator temperature for four months. After this period the antioxidant properties of kombucha are no longer retained.     

Total Phenolic Content and Antioxidant and Antimicrobial Activities of Papaver rhoeas L. Organ Extracts Growing in Taounate Region,Morocco

The objective of this study is to valorize Papaver rhoeas L. from the Taounate region of Morocco by determining the total polyphenol content (TPC), the total flavonoid content (TFC) and the antioxidant and antimicrobial activities of four organs. The quantification of TPC and TFC in root, stem, leaf and flower extracts (RE, SE, LE and FE, respectively) was estimated by the Folin–Ciocalteu reaction and the aluminum trichloride method, respectively. Two tests were used to assess antioxidant power: the DPPH test and TAC assay. The antimicrobial activity was studied against five pathogenic bacteria and yeast, using two methods: disk diffusion and microdilution. The TPC in LE and LF was twice as high as that in RE and SE (24.24 and 22.10 mg GAE/g, respectively). The TFC values in the four extracts were very close and varied between 4.50 mg QE/g in the FE and 4.38 mg QE/g in the RE. The LE and FE showed low DPPH values with IC50 = 0.50 and 0.52 mg/mL, respectively. The TAC measurement revealed the presence of a significant amount of antioxidants in the studied extracts, mainly in LE and FE (6.60 and 5.53 mg AAE/g, respectively). The antimicrobial activity results revealed significant activity on almost all of the tested strains. The MIC of FE and SE against E. coli 57 was 1.56 and 0.78 mg/mL, respectively, while against the S. aureus it was 50 and 25 mg/mL, respectively. The low MLC value (1.56 mg/mL) was recorded against E. coli 57 by RE and SE.     

Impact of Brewing Methods on Total Phenolic Content (TPC) in Various Types of Coffee

Coffee is a widely consumed beverage, both in Europe, where its consumption is highest, and on other continents. It provides many compounds, including phenolic compounds. The aim of the study was to assess the effect of various brewing methods on the total phenolic content (TPC) in the infusion. Research material comprised commercially available coffees: Instant Arabica and Robusta, freshly ground Arabica and Robusta (immediately prior to the analysis), ground Arabica and Robusta, decaffeinated Arabica, and green Arabica and Robusta. The following preparation methods were used: Pouring hot water over coffee grounds or instant coffee, preparing coffee in a percolator and using a coffee machine. Additional variables which were employed were water temperature (90 or 100 °C) and its type (filtered or unfiltered). In order to determine the impact of examined factors, 225 infusion were prepared. Total phenolic content was determined by the spectrophotometric method using the Folin-Ciocalteu reagent and the obtained results were expressed in mg gallic acid (GAE) per 100 g of brewed coffee. The highest value was obtained for 100% Arabica ground coffee prepared in a coffee percolator using unfiltered water at a temperature of 100 °C: 657.3 ± 23 mg GAE/100 g of infusion. High values were also observed for infusions prepared in a coffee machine, where the highest TPC value was 363.8 ± 28 mg GAE/100 g for ground Arabica. In turn, the lowest TPC was obtained for Arabica green coffee in opaque packaging, brewed with filtered water at a temperature of 100 °C: 19.5 ± 1 mg GAE/100 g of infusion. No significant effect of temperature and water type on the TPC within one type of coffee was observed. Due to its high content of phenolic compounds, Arabica coffee brewed in a coffee percolator should be the most popular choice for coffee drinkers.     

Effect of Extraction Method on Total Flavonoid,Total Phenolic Content,Antioxidant and Anti-bacterial Activity of Zingiberis Officinale Rhizome

This research aims to compare between decocta and maceration method using water and ethanol as a solvent on total flavonoid, total phenolic content, antioxidant and antibacterial activity of Zingiber officinale rhyzome extract. The Rhyzome was dryed by oven method on 50 °C for 24 hours and 48 hours. Total flavonoid, total phenolic content and antioxidant activity were assay by spectrophotometric method. The antibacterial activity was determined by difussion agar method against Bacillus subtilis (Bs) and Escherichia colli InaCC B5 (Ec). Ethanol extract from dried rhyzome processed for 24 hours (R-24) indicated the best result for total flavonoid, total phenolic content and antioxidant activity. The yield of total flavonoid for R-24 was 286 μg/mL. The yield of total phenolic content for R-24 was 504 μg/mL and the yield of IC₅₀ antioxidant activity for R-24 was 5.753 μg/mL. The extract should antibacterial activity againts Bs with inhibition diameter of 10% and 20% of samples concentration are 10 and 11.5 mm respectively. Meanwhile, The inhibition diameter result against Ec for 10% and 20% of samples concentration are 7.5 and 8.5 mm respectively.     

Analysis of the Leaves and Cones of Lithuanian Hops (Humulus lupulus L.) Varieties by Chromatographic and Spectrophotometric Methods

This work involves a comprehensive chemical composition analysis of leaf and cone samples of Lithuanian hop varieties. This study aimed to determine the chemometric properties of the leaves and cones of five Lithuanian hop varieties. Determined properties were the following: (a) xanthohumol content, (b) phenolic compounds, (c) flavonoids, (d) radical scavenging activity, and (e) the qualitative composition of volatile compounds. The total content of phenolic compounds in aqueous 75% methanolic extracts varied between 31.4–78.2 mg of rutin equivalents (RE)/g, and the concentration of flavonoids was between 11.0–23.3 mg RE/g. Radical scavenging activity varied between 34.4–87.2 mg RE/g. A QUENCHER analysis procedure showed 91.7–168.5 mg RE/g of the total phenolic compound content, 12.7–21.4 mg RE/g of flavonoids, and 48.4–121.0 mg RE/g of radical scavenging activity. ‘Fredos taurieji’ and ‘Fredos derlingieji’ varieties have shown maximum values of phenolic compounds and radical scavenging activity both in leaf and cone suspensions. These varieties accumulated a higher amount of xanthohumol in leaves. The concentration of xanthohumol in the samples varied between 0.0014–0.2136% of dry mass, with the highest concentration in the cones of ‘Kauno gražieji’. We identified 19 volatile compounds in leaves, and in cones, we identified 32. In both of them, α-humulene and β caryophyllene dominated. ‘Raudoniai’ leaves were exceptional in their aroma due to dominating compound nagina ketone (Kovats index 1306). The QUENCHER procedure has shown a great potential for the unextractable residue of hop raw material. Further investigation and valorization of different hop biomass components, not only cones, are essential.     

Screening of antioxidant activity and volatile compounds composition of Chamerion angustifolium (L.) Holub ecotypes grown in Lithuania

Since biological activity of medicinal plants is dependent on cultivation area, climatic conditions, developmental stage, genetic modifications and other factors, it is important to study flora present in different growing sites and geographical zones. This study was focused on screening of antioxidant activity of C. angustifolium harvested in six different locations in Lithuania. The total contents of phenolic compounds, flavonoids and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity were evaluated by spectrophotometric methods. A correlation between radical scavenging activity and total phenolic compounds content was observed (correlation coefficient 0.98). HPLC with online post-column DPPH radical scavenging reaction detection was used for the separation of extracts. Oenothein B, rutin and one unidentified compound were predominant. Volatile compounds were analysed using solid-phase microextraction coupled with gas chromatography–mass spectrometry. Based on the analysis of volatiles, all samples were classified into two chemotypes: (I) with predominant α- and β-caryophyllenes and (II) with predominant anethole.     

Determination of the Free Radical Scavenging Activity of Lycium Extracts

Lycium species growing in Turkey have not so far been studied sufficiently. For this reason, non-polar and polar extracts obtained from the fruits of Lycium barbarum L. and L. Ruthenicum Murray (Solanaceae) were assessed both in vitro for their potential as free radical scavenger crude extracts and their phenolic composition. Fruits of Lycium species were sequentially extracted with petroleum ether, ethyl acetate, methanol, n-butanol, and water in a Soxhlet extractor. All the extracts were assessed for the scavenging of the nitrogen-centered free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH^.) by in vitro method. Furthermore, the composition of each extract was investigated both in terms of its Folin-Ciocalteau reactive components and its qualitative content. The phenolic compounds within the extracts were determined as benzoic acid and hydroxycinnamic acid derivatives, flavonoids, and anthocyanins according to their retention time and UV spectral data by HPLC-DAD system.     

A DFT study on the radical scavenging activity of hydroxyanthraquinone derivatives in rhubarb

The structural and electronic properties of hydroxyanthraquinone derivatives in rhubarb, namely, chrysophanol, emodin, physcion, aloe‐emodin, rhein, and their radicals were investigated at density functional level. The bifurcated hydrogen bond property of the studied structures was investigated using the atoms in molecules theory. It turned out that the presence of the dihydroxy functionality increases the radical stability through hydrogen bonds formation and favors hydrogen atom abstraction. Bond dissociation energy and ionization potential were also determined to know if the radical scavenging activity of these compounds proceeds via an H‐atom or an electron‐transfer mechanism. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Effects of Extraction Methods on the Bioactivities and Nutritional Value of Virginia and Valencia-Type Peanut Oil

This study aimed to evaluate the effects of peanut varieties cultivated in Morocco (Virginia and Valencia) and extraction methods (cold press, CP; Soxhlet, Sox and maceration, and Mac) on the fatty acid profile, phytosterol, and tocopherol contents, quality characteristics, and antioxidant potential of peanut seed oil. The DPPH method was used to determine the antioxidant activity of the oils. The results revealed that fatty acid content was slightly affected by the extraction technique. However, the CP method was shown to be an excellent approach for extracting oil with desirable quality features compared to the Sox and Mac methods. Furthermore, the peanut oil extracted via CP carried a higher amount of bioactive compounds and exhibited remarkable antioxidant activities. The findings also revealed higher oleic acid levels from the Virginia oil, ranging from 56.46% to 56.99%. Besides, a higher total phytosterol and tocopherol content and DPPH scavenging capacity were obtained from the Valencia oil. Analyzing the study, it can be inferred that extraction method and variety both affect the composition of the peanut oil’s bioactive compounds and antioxidant activity. This information is relevant for extracting peanut oil with a greater level of compounds of industrial interest.     

Phenolic compounds from the aerial parts of Clematis viticella L. and their in vitro anti-inflammatory activities*

Phytochemical investigations on the EtOH extract of Clematis viticella led to the isolation of six flavonoid glycosides, isoorientin (1), isoorientin 3′-O-methyl ether (2), quercetin 7-O-α-L-rhamnopyranoside (3), quercetin 3,7-di-O-α-L-rhamnopyranoside (4), manghaslin (5) and chrysoeriol 7-O-β-D-glucopyranoside (6), one phenylethanol derivative, hydroxytyrosol (7), along with three phenolic acids, caffeic acid (8), (E)-p-coumaric acid (9) and p-hydroxybenzoic acid (10). The structures of the isolates were elucidated on the basis of NMR and HR-MS data. All compounds were isolated from C. viticella for the first time. Compounds 7 and 8 showed significant anti-inflammatory activity at 100 μM by reducing the release of NO in LPS-stimulated macrophages comparable to positive control indomethacin. Compounds 3 and 7 exhibited anti-inflammatory activity through lowering the levels of TNF-α while 1, 3 and 5 decreased the levels of neopterin better than the positive controls.     

Content of Phenolic Compounds in Meadow Vegetation and Soil Depending on the Isolation Method

The aim of this paper was to determine the effect of the hydrolysis method on the amounts of phenolic compounds in the plant material in soil and, as a consequence, on the parameters to determine the degree of lignins transformation in soils. The study included the plant material (hay, sward, and roots) and soil—Albic Brunic Arenosol (horizon A, AE, and Bsv) samples. Phenolic compounds were isolated at two stages by applying acid hydrolysis followed by alkaline re-hydrolysis. The quantitative and qualitative analysis of phenolic compounds was performed with high-performance liquid chromatography with a DAD. The content of phenolic compounds in the extracts depended on the hydrolysis method and it was determined by the type of the research material. The amounts of phenolic compounds contained in the alkaline hydrolysates accounted for 55.7% (soil, horizon Bsv)—454% (roots) of their content in acid hydrolysates. In the extracts from acid hydrolysates, chlorogenic and p-hydroxybenzoic acids were dominant. In the alkaline extracts from the plant material, the highest content was recorded for p-coumaric and ferulic acids, and in the extracts from soil, ferulic and chlorogenic acids. A combination of acid and alkaline hydrolysis ensures the best extraction efficiency of insoluble-bound forms of polyphenols from plant and soil material.     

Influence of Extraction Solvent on the Phenolic Profile and Bioactivity of Two Achillea Species

The phenolic composition, as well as the antioxidant and antimicrobial activities of two poorly investigated Achillea species, Achillea lingulata Waldst. and the endemic Achillea abrotanoides Vis., were studied. To obtain a more detailed phytochemical profile, four solvents with different polarities were used for the preparation of the plant extracts whose phenolic composition was analyzed using UHPLC-MS/MS (ultra-high performance liquid chromatography-tandem mass spectrometry). The results indicate that both of the investigated Achillea species are very rich in both phenolic acids and flavonoids, but that their profiles differ significantly. Chloroform extracts from both species had the highest yields and were the most chemically versatile. The majority of the examined extracts showed antimicrobial activity, while ethanolic extracts from both species were potent against all tested microorganisms. Furthermore, the antioxidant activity of the extracts was evaluated. It was found that the ethanolic extracts possessed the strongest antioxidant activities, although these extracts did not contain the highest amounts of detected phenolic compounds. In addition, several representatives of phenolic compounds were also assayed for these biological activities. Results suggest that ethanol is a sufficient solvent for the isolation of biologically active compounds from both Achillea species. Moreover, it was shown that the flavonoids naringenin and morin are mainly responsible for these antimicrobial activities, while caffeic, salicylic, chlorogenic, p-coumaric, p-hydroxybenzoic, and rosmarinic acid are responsible for the antioxidant activities of the Achillea extracts.     

Effect of Elicitation with Iron Chelate and Sodium Metasilicate on Phenolic Compounds in Legume Sprouts

Seven-day-old sprouts of fenugreek (Trigonella foenum-graecum L.), lentil (Lens culinaris L.), and alfalfa (Medicago sativa L.) were studied. The legume seeds and then sprouts were soaked each day for 30 min during 6 days with water (control) or mixture of Fe-EDTA and sodium silicate (Optysil), or sodium silicate (Na-Sil) alone. Germination and sprout growing was carried out at temperature 20 ± 2 °C in 16/8 h (day/night) conditions. Phenolic compounds (free, ester, and glycosides) content were determined by HPLC-ESI-MS/MS using a multiple reaction monitoring of selected ions. Flavonoids and phenolic acids were released from their esters after acid hydrolysis and from glycosides by alkaline hydrolysis. The presence and high content of (−)-epicatechin (EC) in fenugreek sprouts was demonstrated for the first time. Applied elicitors decreased the level of free EC in fenugreek and alfalfa sprouts but enhanced the content of its esters. Besides, elicitors decreased the content of quercetin glycosides in lentil and fenugreek sprouts but increased the content of quercetin and apigenin glycosides in alfalfa sprouts. The applied elicitors decreased the glycoside levels of most phenolic acids in lentil and p-hydroxybenzoic acid in fenugreek, while they increased the content of this acid in alfalfa. The mixture of iron chelate and sodium silicate had less effect on changes in flavonoid and phenolic acid content in legume sprouts than silicate alone. In general, the used elicitors increased the content of total phenolic compounds in fenugreek and alfalfa sprouts and decreased the content in lentil sprouts. Among the evaluated elicitors, Optysil seems to be worth recommending due to the presence of iron chelate, which can be used to enrich sprouts with this element.     

黄树莓叶片中黄酮类物质的提取及抗氧化性

黄酮类物质具有降血糖、降血脂、抗心律失常、抗氧化高效性与低毒性、抗衰老等生理活性1 2 。从药食两种植物中筛选出高效低毒且经济的抗氧化性强的物质 ,必将是近一步开发天然高效食品抗氧化剂的重要途径[3 5] 。黄树莓是我国北方地区小浆果树种之一 ,其中以黑龙江分布较多。黄树莓的浆果甜而芳香 ,营养丰富 ,是鲜美的生食果品 ,也可加工制成果酱、果酒、果汁和蜜饯等。它又是密源植物和药用植物 ,有止渴、痰、发汗、活血的效用。本实验以测定黄树莓叶片总黄酮含量并考察了提取物粗黄酮对猪油的抗氧化性。1　实验部分1 1　主要试剂及仪…     

Optimization of Maceration Conditions for Improving the Extraction of Phenolic Compounds and Antioxidant Effects of Momordica Charantia L. Leaves Through Response Surface Methodology (RSM) and Artificial Neural Networks (ANNs)

The main goals of this research were the chemical and biological characterization of the bitter melon (Momordica charantia) isolate obtained by traditional (maceration) extraction, as well as optimization of this process using response surface methodology (RSM) and artificial neural networks (ANNs). Experiments were performed using Box–Behnken experimental design on three levels and three variables: extraction temperature (20?°C, 40?°C, and 60?°C), solvent concentration (30%, 50%, and 70%) and extraction time (30, 60, and 90?min). The measurements consisted of 15 randomized runs with 3 replicates in a central point. The antioxidant activity of obtained extracts was determined by the 1,1-diphenyl-2-picrylhydrazyl (DPPH), cupric ion reducing antioxidant capacity (CUPRAC) and ferric reducing antioxidant power (FRAP) assays while chemical characterization was done in terms of the total phenolic content (TPC). The methodology shows positive influence of solvent concentration on all four observed outputs, while temperature showed a negative impact. RSM showed that the optimal extraction conditions were 20?°C, 70% methanol, and an extraction time of 52.2?min. Under these conditions, the TPCs were 20.66 milligrams of gallic acid equivalents (mg GAE/g extract), DPPH 30.22 milligrams of trolox equivalents (mg TE/g extract), CUPRAC 67.78 milligrams of trolox equivalents (mg TE/g extract), and FRAP 45.48 milligrams of trolox equivalents (mg TE/g extract). The neural network coupled with genetic algorithms (ANN-GA) was also used to optimize the conditions for each of the outputs separately. It is anticipated that results reported herein will establish baseline data and also demonstrate that that the present model can be applied in the food and pharmaceutical industries.     

Impact of Drying Methods on Phenolic Components and Antioxidant Activity of Sea Buckthorn (Hippophae rhamnoides L.) Berries from Different Varieties in China

Sea buckthorn berries are rich in bioactive compounds and can be used for medicine and food. The variety and drying method used have an important influence on quality. In this study, different sea buckthorn varieties from China were selected and dried with four common drying methods. The total phenolic content (TPC), total flavonoids content (TFC), contents of 12 phenolic compounds and antioxidant capacity in vitro were analyzed. The results showed that the TPC, TFC and antioxidant activity of two wild sea buckthorn berries were higher than those of three cultivated berries, and for the same varieties, measured chemical contents and antioxidant activity of the freeze-dried fruit were significantly higher than those obtained with three conventional drying methods. In addition, forty-one compounds in sea buckthorn berry were identified by UPLC-PDA-Q/TOF-MS, most of which were isorhamnetin derivatives. Multivariate statistical analysis revealed narcissin and isorhamnetin-3-O-glucoside varied significantly in sea buckthorn berries of different varieties and with different drying methods; they were potential quality markers. Strong correlations were found between TPC, gallic acid and antioxidant capacity (p < 0.05). The results revealed how components and antioxidant activity varied in different sea buckthorn, which provides a valuable reference for quality control and further development and utilization of sea buckthorn.     

Effects of Different Extraction Methods in Pharmacopoeia on the Content and Structure Transformation of Ginsenosides

Ginseng (Panax ginseng C. A. Meyer), a perennial herb, possesses immunostimulatory, anticarcinogenic, antiemetic, and antioxidative biological activities. In recent years, more and more people have paid attention to the extraction methods and quality evaluation of ginseng. China, the United States, Europe, Japan, and Korea have all had the quality standards and content determination methods of ginseng. The different treatment methods are adopted before the determination of ginseng samples and the content limits of the index components, such as ginsenoside Rb₁, ginsenoside Rg₁, and ginsenoside Re exist differences. The similarities and differences of ginseng content detection methods in pharmacopoeias of different countries have been analyzed by a research group, but the comparison of the effects of different methods on the ginsenoside content and structural transformation has not been reported. In this paper, ginsenosides in ginseng were extracted according to four national pharmacopoeias and analyzed quantitatively and qualitatively by UPLC-Q-Exactive-MS and HPLC-UV. It was illustrated that the pretreatment method has a significant influence on the content determination of ginseng. The yield of rare saponins was increased by heating concluded from both the qualitative and quantitative comparison. Finally, a simple and feasible extraction method was optimized by response surface method at room temperature. The analysis of the preparation method and process optimization of the four pharmacopoeias can provide important reference information for the revision of ginseng standards.     

Effects of Enzymatic Pretreatment of Seeds on the Physicochemical Properties,Bioactive Compounds,and Antioxidant Activity of Pomegranate Seed Oil

Enzymatic pretreatment of seeds is a novel approach that enhances the health benefits of the extracted oil. The study investigated the influence of the enzymatic pretreatment of seeds on the quality of oil from different pomegranate cultivars. The quality of the ultrasound-assisted (and ethanol-extracted) oil was studied, with respect to the refractive index (RI), yellowness index (YI), conjugated dienes (K232), peroxide value (PV) ρ-anisidine value (AV), total oxidation value (TOTOX), total carotenoid content (TCC), total phenolic compounds (TPC), fatty acid composition, phytosterol composition, ferric reducing antioxidant power (FRAP), and 2.2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging capacity. The seeds of three different pomegranate cultivars (‘Wonderful’, ‘Herskawitz’, and ‘Acco’) were digested with an equal mixture of Pectinex Ultra SPL, Flavourzyme 100 L, and cellulase crude enzymes, at a concentration, pH, temperature, and time of 1.7%, 4.5, 40 °C, and 5 h, respectively. Enzymatic pretreatment of PS increased oil yield, PV, TPC, TCC, and DPPH radical scavenging capacity, but decreased the YI. The levels of K232, AV and TOTOX, fatty acids, phytosterols, RI, and FRAP, were not significantly affected by enzymatic pretreatment of PS. Principal component analysis (PCA) established that oil extracted from the ‘Acco’ seed after enzymatic pretreatment had higher yield, TPC, TCC, and DPPH radical scavenging capacity. Therefore, enzyme-pretreated ‘Acco’ pomegranate fruit seed is a source of quality seed oil with excellent antioxidant properties.     

亚/超临界乙醇中羟基和氢自由基作用下的纤维素液化行为

以水杨酸为羟基自由基(HO·)捕捉剂、四氯化碳为氢自由基(H·)捕捉剂,采用间歇高压反应釜对玉米秸秆纤维素在亚/超临界乙醇中的液化行为进行了研究,通过考察自由基捕捉剂用量、反应温度和反应时间对纤维素液化行为的影响,研究亚/超临界乙醇产生的HO·和H·自由基对纤维素的液化作用。结果表明,随着水杨酸用量增加(0-4mL),HO·浓度升高,生物油收率由29.3%提高至47.9%,固体残渣收率从26.7%降低至24.3%;反应温度从250℃升高至320℃,HO·活性随之增强,生物油收率由35.9%升高至58.2%,固体残渣收率由51.8%降低至20.4%;随着四氯化碳用量由0增加为2mL时,H·浓度降低,生物油收率由24.7%降低至20.7%,固体残渣收率由54.1%增加至59.1%;反应时间从0到30min,液化作用不断增强,生物油收率从8.7%升高至28.5%,固体残渣收率由86.3%下降至60.9%;30min之后,四氯化碳对H·活性的抑制加强,导致液化作用减弱,生物油收率有所下降。实验结果表明,乙醇在亚/超临界状态下能够产生HO·和H·,且HO·和H·浓度和活性与反应条件相关,对纤维素液化产物的收率及其分布具有明显的影响。     

Effects of Ag Doping Content and Dispersion on the Photocatalytic and Antibacterial Properties in ZnO Nanoparticles

ZnO nanoparticles(NPs)with different contents of Ag dopants were obtained by one-step solvothermal method.The crystalline structures of the prepared composites were characterized by means of X-ray diffraction(XRD).The morphology and composition of the samples were studied by means of scanning transmission electron microscopy(TEM)5 X-ray photoelectron spectroscopy(XPS)and electron microscopy(SEM).Photoluminescence(PL)spectra have been used to investigate pure ZnO,Ag-ZnO and Ag-ZnO-PVP NPs to determine the effect of composition on PL properties.It was found that the Ag-ZnO samples showed stronger emissions than pure ZnO.The catalytic activity of samples was measured by the degradation rate of R6G,which exhibited that Ag-ZnO nanocomposite demonstrated enhanced photocatalytic activity compared to the pure ZnO NPs.The possible influence factors to the photocatalytic and antibacterial activities of the sample were explored,including Ag contents and dispersion.It was presented that the photocatalytic activity of Ag-ZnO-PVP was better than that of Ag-ZnO and it showed the highest photocatalytic activity with 7%of Ag content.The Ag-ZnO-PVP can kill the Escherichia coli(E.coli)cells.