阻抑动力学光度法测定环境水样中苯胺

基于在乙酸-乙酸钠缓冲溶液介质中,痕量苯胺能灵敏地阻抑过氧化氢氧化溴甲酚绿褪色。研究了该阻抑褪色反应的最佳条件及动力学参数,建立了测定痕量苯胺的方法。该法的线性范围为0~45.0μg.L-1,检出限为4.30μg.L-1。用于环境水样中痕量苯胺的测定,结果的RSD值在2.35%~3.78%之间,回收率在95.8%~103.6%。     

3‐O‐Methylquercetin Glucosides from Ophioglossum pedunculosum and Inhibition of Lipopolysaccharide‐Induced Nitric Oxide Production in RAW 264.7 Macrophages

The three new 3‐O‐methylquercetin glucosides 1 – 3 , together with three known congeners and 3‐O‐methylquercetin, were isolated from the fern Ophioglossum pedunculosum (quercetin=2‐(3,4‐dihydroxyphenyl)‐3,5,7‐trihydroxy‐4H‐1‐benzopyran‐4‐one). The new compounds were identified on the basis of spectroscopic analysis as 5′‐isoprenyl‐3‐O‐methylquercetin 4′,7‐di‐β‐D ‐glucopyranoside ( 1 ), 3‐O‐methylquercetin 4′‐β‐D ‐glucopyranoside 7‐[O‐β‐D ‐glucopyranosyl‐(1→2)‐β‐D ‐glucopyranoside] ( 2 ), and 3‐O‐methylquercetin 7‐[O‐β‐D ‐glucopyranosyl‐(1→2)‐β‐D ‐glucopyranoside] ( 3 ). The effect of the isolated compounds on lipopolysaccharide (LPS)‐induced NO production was evaluated. The inhibitory activity of 3‐O‐methylquercetin derivatives decreased markedly with the increasing number of glucosyl groups in the structures.     

Profile characterization and biological activities of cold pressed Garden Cress (Lepidium sativum) seed oil

Lepidium sativum is cultivated mainly for the edible oil from its seeds, and considered as an unutilized and neglected crop despite its important properties. Its oil fraction is used to produce soap and stabilize linseed oil when it is mixed with wild mustard seed oil. Once converted into fatty acid methyl esters, it represents a good substitute for imported petroleum diesel after alkaline transesterification reaction. In the current study, Lepidium sativum seeds cultivated in Tunisia and the physicochemical properties and nutrient profile of its cold pressed seed oil were investigated. The antioxidant, antibacterial, and anti-inflammatory activities of the above oil were also assessed. Lepidium sativum seed oil was abundant in both linolenic (35.59 ± 1.9%) and oleic (21.14 ± 0.63%) acids, and high amounts of β-sitosterol (42.57 ± 2.96 mg/100 g), campesterol (20.04 ± 1.4 mg/100 g) and Δ 5,24 stigmastadienol (11.82 ± 0.45 mg/100 g) were detected. The total tocopherol content of Lepidium sativum seed oil reached 136.83 ± 7.6 mg/100 g with a predominance of γ-tocopherol (86.23%). Its seed oil exhibited an IC₅₀ of 10.33 ± 0.05 mg/mL and a radical scavenging activity of 415.6 ± 40 Trolox Equivalent Antioxidant Capacity (TEAC) for the DPPH and the ABTS assays, respectively. While the thermal analysis proved a high thermal stability of Lepidium sativum seed oil, that of eight bacteria and one fungal strain showed no noticeable bacterial or antifungal effects. It was also revealed that Lepidium sativum seed oil held a remarkable anti-inflammatory activity. Hence, the obtained results evidenced remarkable chemical, antioxidant and anti-inflammatory properties of Lepidium sativum seed oil, which might potentially be promising for enhancing human health and preventing age-related diseases.     

Phytochemical prospection,evaluation of antibacterial activity and toxicity of extracts of Libidibia ferrea (Mart. ex Tul.) L.P. Queiroz

Libidibia ferrea (Mart. ex Tul.) L.P. Queiroz is a arboreal species found in the Caatinga from Northeast of Brazil that has been used in popular medicine as an anti-inflammatory, healing, analgesic and for the treatment of respiratory system disorders. Therefore, the objective of this work was to evaluate the composition of ethanol extracts from the leaves and inner bark of Libidibia ferrea, as well as to verify its antibacterial activity and as a potential inhibitor of the TetK efflux pump in Staphylococcus aureus strains, in addition to investigating the toxicity of the extracts in a Drosophila melanogaster model. The analysis and quantification of the extracts markers was performed by High Performance Liquid Chromatography (HPLC). To determine the Minimum Inhibitory Concentration (MIC) broth microdilution tests were carried out. The evaluation of efflux pump inhibition was performed by modifying the MIC of antibiotics and ethidium bromide. Mortality and negative geotaxis tests were used to verify the toxicity of extracts on D. melanogaster. Hydrolysable tannins (gallic acid and ellagic acid) and flavonoids were found in HPLC analysis. The extracts did not show antibacterial activity, demonstrating a MIC ≥ 1024 µg/mL, however the ethanolic extract of the leaves decreased the MIC of the antibiotic from 64 µg/mL to 16 µg/mL, but this effect is not associated with the inhibition of the efflux pump. The extracts did not show toxicity in a D. melanogaster model. This is the first study to evaluate the antibacterial activity of L. ferrea extracts on the IS-58 strain of S. aureus, as well as the first to investigate its toxicity using D. melanogaster. From the results, further studies are needed to determine the mechanisms of action of the extract with other antibiotics.     

Neural signal transduction aided by noise in multisynaptic excitatory and inhibitory pathways with saturation

We study the stochastic resonance phenomenon in saturating dynamical models of neural signal transduction, at the synaptic stage, wherein the noise in multipathways enhances the processing of neuronal information integrated by excitatory and inhibitory synaptic currents. For an excitatory synaptic pathway, the additive intervention of an inhibitory pathway reduces the stochastic resonance effect. However, as the number of synaptic pathways increases, the signal transduction is greatly improved for parallel multipathways that feature both excitation and inhibition. The obtained results lead us to the realization that the collective property of inhibitory synapses assists neural signal transmission, and a parallel array of neurons can enhance their responses to multiple synaptic currents by adjusting the contributions of excitatory and inhibitory currents.     

叠氮化钠对辣根过氧化物酶的荧光猝灭机制的研究

研究了辣根过氧化物酶 (HRP)和叠氮化钠 (NaN3 )作用前后的荧光光谱变化。探讨了HRP的荧光猝灭机制 ,首次运用了HRP的荧光猝灭行为确认了HRP和NaN3 之间生成了配合物。计算了HRP和NaN3 之间生成的配合物的形成常数为 7 9× 10 8L·mol-1,结合位点数为 1。研究还发现 ,NaN3 与HRP的结合 ,影响了分子构象 ,使酪氨酸和色氨酸残基的微环境受到不同程度的影响。     

阻抑过氧化氢氧化甲基橙退色反应分光光度法测定Ge-132

基于微量 Ge- 1 32对过氧化氢氧化甲基橙退色反应有阻抑作用 ,提出了阻抑退色光度法测定微量Ge- 1 32的新方法。该方法线性范围为 6 .88— 2 4.0 8μg/m L。用于模拟样品的测定 ,回收率在 93%— 99%范围内。     

过氧化物酶催化反应的底物结构的研究

研究了２３种物对过氧化物酶催化过氢氧化佳味醇反应的竞争性抑制作用，提出抑制常数Ｋｉ值的计算方法，并通过对各种物质抑制常数大小的比较和分析，提出了过氧化物酶催化氧化还原反应的最佳底物结构。