Inhibition of gut bacterial β-glucuronidase by chemical components from black tea: Inhibition interactions and molecular mechanism

Gut bacterial β-glucuronidase is regarded as an important molecular target for several therapeutic applications. Inhibitors of β-glucuronidase can effectively alleviate the drug-induced gastrointestinal tract toxicity. In this study, the ethanol extracts of black tea was found to display significant inhibitory activities against Escherichia coli β-glucuronidase (EcGUS), and seven polyphenols including catechins and theaflavins were identified as the key components responsible for the strong inhibitory potency of black tea towards EcGUS. Among these seven identified naturally occurring inhibitors, (−)-catechin gallate (CG), theaflavin-3-monogallate (TF-3-G), theaflavin-3′-monogallate (TF-3′-G) and theaflavin-3,3′-digallate (TFDG) were more potent inhibitors of EcGUS compared with (−)-epicatechin gallate (ECG), (−)-gallocatechin gallate (GCG), and (−)-epigallocatechin gallate (EGCG). Furthermore, molecular docking and molecular dynamics simulation results further indicated that TFDG could bind in the cavity of EcGUS and interacted with key residues Ser360, Glu413 and Ile560 of EcGUS through hydrogen bonds. Taken together, these data offer important information for efficient development of black tea and its catechins and theaflavins constituents for treating drug-induced enteropathy.     

Simple and sensitive fluorimetric method for determination of environmental hormone bisphenol A based on its inhibitory effect on the redox reaction between hydroxy radical and rhodamine 6G [corrected

Peroxyl radical produced by Fenton-like reagent (Fe(III) + H₂O₂) oxidizes Rhodamine 6G and produces the quenching of its fluorescence. It is also found that bisphenol A has an inhibitory effect on the redox reaction. Based on this observation, an inhibitory kinetic fluorimetric method is reported for the determination of trace bisphenol A. The fluorescent inhibition of rhodamine 6G is measured by fix-time method. Under the optimum experimental conditions, the detection limit and the quantification limit for bisphenol A is 2.0 and 6.7 ng mL⁻¹, respectively; and the linear range of the determination is 0.024-0.4 μg mL⁻¹. The proposed method has been used for the determination of bisphenol A in environmental waters, river bottom sediment, generic soil, polycarbonate products and teeth filling samples with recoveries of 92.5-110.0%. The possible mechanism of the reaction has also been discussed.     

阻抑动力学光度法测定绞股蓝中痕量钴

基于钴(Ⅱ)在稀硫酸介质中对乙二胺四乙酸活化重铬酸钾氧化丁基罗丹明B的阻抑反应,建立了阻抑动力学光度法测定痕量钴(Ⅱ)的方法。检出限为2.65×10-6g.L-1,线性范围为0~0.60μg/25 mL,RSD<4%,平均回收率为98.5%,应用于实际样品中痕量钴的测定。     

(8R,13R)-8,12,13,17-四氢穿心莲内酯的合成、晶体结构和葡萄糖苷酶抑制活性

设计并合成了新的具有旋光活性的二萜类内酯衍生物2, 并通过NMR, IR, HRMS和X射线单晶衍射等技术分析了其结构和绝对构型.     

阻抑动力学分光光度法测定微量硒

基于在pH 6.09的B-R缓冲溶液中,Se（Ⅳ）对H₂O₂氧化甲基紫的褪色反应具有阻抑作用,建立了阻抑动力学分光光度法测定微量Se（Ⅳ）的新方法。方法的线性范围为:0.020—0.080μg/mL,检出限为1.44×10^-3μg/mL,用于环境水样中微量Se（Ⅳ）的测定,结果满意。     

人工神经网络阻抑动力学光度法同时测定对苯二胺和间苯二胺

在硫酸性介质中,Fe(Ⅲ)能够催化H2O2氧化甲基红褪色反应,对苯二胺和间苯二胺都能阻抑该催化氧化褪色反应的速度,两者对Fe(Ⅲ)催化H2O2氧化甲基红褪色反应阻抑作用不具有加和性,根据这一现象,用人工神经网络处理非线性体系的优势进行数据处理,从而建立了一种新的测定对苯二胺和间苯二胺混合物的人工神经网络阻抑动力学光度法。对6组混合样品进行测定,回收率均在95%～105%之间。该方法运用于实验室水样的分析。     

人工神经网络阻抑动力学光度法同时测定对苯二酚和邻苯二胺

在酸性介质中,F e（Ⅲ）能够催化H2O2氧化中性红褪色反应,而对苯二酚和邻苯二胺都能阻抑该催化氧化褪色反应的速度。但二者存在一定的速率差异,且吸光度的加和性不佳。结合人工神经网络提出了一种能同时测定对苯二酚和邻苯二胺的新方法。研究了最佳反应和测定条件,结果表明：1.0×10^-3m o.lL-1中性红溶液用量为0.8mL;30%H2O2用量为0.6mL;0.100g.L-1F e（Ⅲ）标准溶液用量为0.5mL;0.06m o.lL-1HC l用量为0.8mL;反应时间为6m in;反应温度为75℃时为最佳反应和测定条件。用于混合样品及河水中对苯二酚和邻苯二胺的测定,混合样品中对苯二酚和邻苯二胺回收率分别为95.6%—104.0%、97.8%—104.4%。河水中对苯二酚和邻苯二胺加标回收率均为105%,5次平行测定相对标准偏差分别为3.2%和2.5%。结果满意。     

Secondary Metabolites from the Endophytic Fungus Xylaria cubensis

Seven new metabolites, including three sesquiterpenoids, 10‐hydroxythujopsene ( 1 ), akotriol ( 2 ), and xylaritriol ( 3 ), one diterpenoid, cubentriol ( 4 ), one aliphatic derivative, akoenic acid ( 5 ), one alkaloid, akodionine ( 6 ), and one isocoumarin, akolitserin ( 7 ), together with seven known compounds, 8 – 14 , were isolated from the AcOEt‐soluble fraction of the fermentation broth of the endophytic fungus Xylaria cubensis, derived from the leaves of Litsea akoensis Hayata (Lauraceae). Their structures were elucidated by spectroscopic analyses, including 1D‐ and 2D‐NMR experiments, and by HR‐ESI‐MS mass spectrometry. Among the isolates, (?)‐(R)‐7‐hydroxymellein showed IL‐6 inhibitory activity with an IC₅₀ value of 9.41 μM .     

流动注射在线预富集—同步扫描荧光法分析水样中痕量多环芳烃

建立了苯并［ａ］芘和的流动注射在线预富集－同步扫描荧光检测法，方法简便快速。苯并［ａ］芘和的测定下限分别为０２μｇ／Ｌ和００４μｇ／Ｌ。测定的相对标准偏差分别为：７１１％和７５４％。用于实际水样的测定，苯并［ａ］芘的回收率为９０％～１０３３％，为１０３３％～１１６７％，结果满意。