Short Overview of Some Assays for the Measurement of Antioxidant Activity of Natural Products and Their Relevance in Dermatology

Impaired systemic redox homeostasis is implicated in the onset and development of various diseases, including skin diseases. Therefore, continuous search for natural products with antioxidant bioactivities applicable in biomedicine is attractive topic of general interest. Research efforts aiming to validate antioxidant potentials of natural products has led to the development of several assays based on various test principles. Hence, understanding the advantages and limitations of various assays is important for selection of assays useful to study antioxidant and related bioactivities of natural products of biomedical interest. This review paper gives a short overview on some chemical and cellular bioassays used to estimate the antioxidant activity of chosen natural products together with a brief overview on the use of natural products with antioxidant activities as adjuvant medicinal remedies in dermatology.     

Identification of the decomposition products of nitrobenzanthracenes in solution

Air oxidation products of nitrobenzanthracenes and nitrodibenzanthracenes were separated with high-performance liquid chromatography. The major products were identified as quinones, and the bulk fo the minor products were identified as nitroquinones. Tentative structures are assigned on the basis of mass spectrometry.     

Microbial‐induced synthesis of mineralization products based on the capture of carbon dioxide: Characteristics,reaction kinetics,interfacial adhesion properties,and mechanism of action

As a new type of green environment‐friendly cementitious material, microbial‐induced mineralization products have garnered more and more attention. In this paper, the synthesis of mineralization products under microbial inducement was conducted. The composition and microstructure of mineralization products were studied using energy‐dispersive spectrometer (EDS), X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The results showed that mineralization products were calcite, while the shape was similar to globular type, and particle size was about 5 μm. The effect of microbial culture solution, secretion solution, and concentration on the conductivity of the solution was compared and analyzed. During the formation of mineralization products, bacterial bodies not only played the role of nucleation sites but also accelerated the deposition of mineralization products. Thus, it could be seen that the bacterial bodies had a certain influence on the reaction kinetics. The adhesion force of mineralization products was evaluated by the interfacial adhesion properties between the mineralization products and glass slides. The results of the sonication test and scratch test indicated that the interfacial adhesion strength between mineralization products and glass slides was closely related to the mass of mineralization products deposited. The larger the mass of mineralization products deposited, the greater the interfacial adhesion strength. Based on the above research and analysis, the reaction process and mechanism model of microbial‐induced mineralization were defined.     

Influence of photo-Fries reaction products on the photodegradation of bisphenol-A polycarbonate

The photodegradation of BPA polycarbonate (PC) can be described as an autoaccelerating process initiated by the formation of biphenol products arising from a formal photo-Fries reaction pathway. Evidence comes from spiking PC films with model compounds of photo-Fries reaction products, pre-exposure of films to generate photo-Fries products, and kinetic analysis. Published data on products formed during natural PC weathering are consistent with this pathway.     

Reactions of aminophosphines with trifluormethanesulfonic acid: phosphenium ion (two-coordinate phosphorus ion) or tricovalent phosphorus products?

The title reaction is shown to give phosphenium ion products (1), mixtures of (10 and tricovalent substitution products (2), or other products, depending on the nature of the substituents on phosphorus.     

基于毛细管电泳的环介导恒温扩增技术检测方法研究

以大肠杆菌(E.coli)为对象,采用环介导恒温扩增技术(LAMP)对其扩增,在实验室自制的毛细管电泳-诱导荧光平台上建立了LAMP产物的检测新方法。引物F3,B3,FIP,BIP扩增的E.coli LAMP产物大小为240 bp。优化的毛细管电泳条件为:毛细管有效长度/总长度(10 cm/15 cm),筛分介质溶液为0.5%羟乙基纤维素(1 300 K),电场强度(100 V/cm),进样条件(100 V/cm,1.0 s)。毛细管电泳时,DNA长度在100~500 bp范围内与其迁移时间呈线性关系,相关系数为0.996。在相同毛细管电泳条件下对E.coli LAMP产物进行分析,并利用这种线性关系在电泳图中对E.coli LAMP产物与假阳性产物做区分,结果表明,毛细管电泳技术不仅可在15 min内实现LAMP产物及附加产物的快速检测,而且可快速区分LAMP阳性及假阳性实验产物。采用建立的毛细管电泳快速检测LAMP产物的方法,对AB0174 E.coli基因实施了LAMP,结果表明该方法适合DNA LAMP产物的快速检测。     

Products of non-flaming combustion of phenol-formaldehyde resin foam

Phenol-formaldehyde foam was decomposed by non-flaming combustion under temperature and atmosphere conditions simulating the main stages of a fire development and the decomposition products were studied. The type and amounts of the products were affected by the decomposition conditions. The residue yield, which was large, decreased with increase in temperature and atmospheric oxygen. Volatile products consisted mostly of light gases with some volatile-condensable products. The volatile products included light hydrocarbons, formaldehyde, phenols, aldehydes, ketones, ethers, oxygen-containing heterocycles, fused ring compounds and benzene and its homologues. The concentration dependence on combustion conditions was studied.     

用组合化学建立天然产物类似物库

天然产物是药物先导化合物的重要来源.组合化学技术在天然产物的研究中起着越来越重要的作用.目前已构建并合成了许多以天然产物为模板的化合物库,为基于天然产物的药物研究开辟了广阔的空间.     

Influence of DSC Measurement Conditions on Kinetic Parameters of Thermal Decomposition of 2,4,6-trinitrotoluene

An autocatalytic model involving the limited solubility of volatile catalytic products was applied to the thermal decomposition of 2,4,6-trinitrotoluene. The critical supersaturation of the thermal decomposition products with the catalytic properties was higher at a low heating rate. Decrease of the sample mass led to an increased critical supersaturation of the decomposition products. This is probably a result of the greater contribution of products adsorption on the aluminium pan surface. It is presumed that the differences observed in the rate constant are connected with the uncontrolled critical supersaturation of the volatile thermal decomposition products. This revised version was published online in August 2006 with corrections to the Cover Date.     

The quality of commercially available herbal products

Herbal products are believed to be safe as they are naturally occurring, however, this is a misconception. Currently, there are many herbal products which are not manufactured under the Good Manufacturing Practice (GMP) guidelines and hence the quality of the product is not controlled. Quality can be assessed by evaluation of data on levels of either active constituent(s) or chemical markers indicative of origin of plant material. Assessment of published data on levels of quality of herbal medicinal products revealed that only a percentage of the total number of products investigated were found to contain the levels of markers as stated on the label, and others had widely varying levels of constituents. Thus few products complied with acceptable quality control standards. Herbal products are increasingly self-prescribed for the treatment of minor ailments. Patients relying on herbal products for therapeutic effects may expose themselves to either low doses of active constituents causing insufficient effects or alternatively take higher levels than expected, with the increased risk of toxicity or adverse effects, or be affected by the inadvertent inclusion of unexpected components with associated potential health risks.     

高效液相色谱-二极管阵列检测法分析原花青素降解产物及副产物

利用高效液相色谱-二极管阵列检测法(HPLC-DAD)研究了不同含水量、不同样品浓度及不同反应时间对原花青素降解(正丁醇/HCl法)产物花青定及反应副产物的影响.木榄花样品经70%丙酮溶液提取,利用Sephadex LH-20柱纯化后得到原花青素样品.配制不同含水量和不同样品浓度的反应溶液,充分震荡后进行正丁醇/HCl法降解.用HPLC-DAD分析不同实验条件下得到的反应产物及副产物.结果表明,反应体系在含水量5%～15%的条件下,转化产物随着反应体系含水量的增加,花青定的转化率也随之增加,副产物的转化率却随之减少,总转化率(即花青定加上副产物的总转化量)呈增加趋势;在反应体系含水量大于15%时,随含水量的增加,转化产物含量呈现下降的趋势;增加反应体系中样品含量并没有明显增加转化产物的转化率,副产物的转化率相对稳定;不同反应时间处理得到的转化产物经HPLC-DAD分析并未发现转化产物花青定和副产物表现出明显的变化规律,总转化率相对稳定.     

Mode of action and biosynthesis of the azabicycle-containing natural products azinomycin and ficellomycin

Only a handful of aziridine-containing natural products have been identified out of the more than 100,000 natural products characterized to date. Among this class of compounds, only the azinomycins (azinomycin A and B) and ficellomycin contain an unusual 1-azabicyclo[3.1.0]hexane ring system, which has been reported to be the reason for theDNAcrosslinking abilities and cytotoxicity of these metabolites. Both families of natural products are produced by Streptomyces species, Streptomyces sahachiroi and Streptomyces ficellus, respectively. Up until recently, much of the work on these molecules has focused on the synthesis of these natural products or their corresponding analogs for in vitro investigations evaluating their DNA selectivity. While one of the most intriguing aspects of these natural products is their biosynthesis, progress made in this area was largely impeded by difficulties with obtaining a reliable culture method and securing a consistent source of these natural products. In this review, we will cover the discovery and biological activity of the azinomycins, their mode of action, related synthetic analogs and biosynthesis, and finish with a discussion on the less studied metabolite, ficellomycin.     

Rhodium-catalyzed reaction of aryl- and alkenylboronic acids with 2,4-dienoate esters: conjugate addition and Heck reaction products

[chemical reaction: see text]. We report herein the first examples of the addition of aryl- and alkenylboronic acids catalyzed by RhI complexes to 2,4-dienoate esters. Three different types of products have been obtained depending on the substitution pattern of the starting ester and the organoboronic acid: 1,6-conjugate addition products, 1,4-conjugate addition products, and Heck reaction products.     

废弃印刷电路板材料裂解产物的高分辨裂解气相色谱-质谱分析

采用高分辨裂解气相色谱-质谱法(PyGC-MS)分析了FR-4型印刷电路板粉末样品的裂解产物。在氦气氛围中,分别在350,450,550,650和750 ℃下对印刷电路板粉末样品进行热裂解,并通过毛细管气相色谱-质谱对裂解产物进行分析,研究了不同裂解温度下裂解产物分布以及主要裂解产物的产率与裂解温度的关系,根据热分解产物的组成,探讨了热分解反应机理。     

Combustion of poly(1-methyl hexamethylene) and poly(1-methyl tetramethylene) and identification of the main decomposition products

The Bayer-ICI-Shell apparatus has been used to carry out combustion experiments on poly(1-methyl hexamethylene) (PH) and poly(1-methyl tetramethylene) (PT) using different air flow rates at various combustion temperatures. The products were adsorbed on charcoal followed by benzyl-alcohol desorption. They were separated and identified using gas chromatography.The non-oxidized products were identified as short chain, saturated and unsaturated hydrocarbons while the main oxidized products are short chain ketones and alcohols. The intensities of the chromatographic peaks of the separated products depend upon the temperatures and air flow rates in the combustion apparatus.     

Size-exclusion chromatography of the soluble lignin products from hydrogen peroxide brightening of mechanical pulps

The molar mass distributions and yields of soluble lignin degradation products formed during the alkaline hydrogen peroxide brightening of spruce mechanical pulp have been determined. These distributions depend on pH, the extent to which the pulp was subjected to solvent extractions, H₂O₂ concentration and reaction time. At and below pH 11, there is an excellent correlation between the brightness and b values on pulp and the amounts of residual peroxide and lignin derived products in solution. Brightening reactions lead primarily to products with intermediate molecular mass values between 1500 and 6000. During multistage brightening, the products formed are initially those with high ionizable phenolic hydroxyl and low carbohydrate contents, and carbonyl-containing moieties. NMR and UV spectroscopic analysis show that products formed include lignin and carbohydrate-containing species. The lignin-originating products from the later stages contain a lower relative concentration of ionizable phenolic groups and more visible-absorbing and carbohydrate-containing species. Brightness and b gains during multistage brightening were exponential with product yield.     

The aminomethylation of adenine,cytosine and guanine

Aminomethylated derivatives of adenine, cytosine and guanine have been isolated and characterized for the first time. These results are important because of the potential for similar adducts being formed transiently between nucleosides and nucleotides, and endogenous aldehydes and amines in vivo, and of the potential use of similar adducts for drug delivery. Mono-alkylated products obtained were from the reaction of adenine with one equivalent of aminomethylating agent derived from amines exhibiting lower basicity (e.g., morpholine and N-methylpiperazine); bis-alkylated products were obtained with agents derived from more basic amines regardless of the stoichiometry. On the other hand, only bis-alkylated products were obtained from the reaction of cytosine or guanine with the aminomethylating agent regardless of the basicity of the secondary amine used or the stoichiometry of the reaction. The mono-alkylated adenine products were alkylated on N-9 while the bis-alkylated cytosine products were alkylated on N-9 and N⁴ and the bis-alkylated adenine products were alkylated on N-9 and N⁶. The adenine and cytosine aminomethyl adducts hydrolyzed rapidly in dilute aqueous solution.     

Radiolysis of nitrate-alcohol binary mixtures at pH 12

Gamma-radiolysis of alkaline binary mixtures of nitrate-alcohol (1-propanol and 1-butanol) has been investigated at a fixed pH of 12. The products of radiolysis, mainly nitrite, aldehyde and hydrogen peroxide were estimated. Also the effect of concentration of each species present in the mixture on the G-values of the products formed has been examined. The G-values of each of the products are found to be lower in basic medium in binary mixtures as compared to those obtained at neutral pH; other conditions being kept constant. However, the yields of products in nitrate solutions show higher values at basic pH in comparison with their counterparts at neutral pH. Results are explained on the basis of reaction mechanism that operates during the process of radiolysis, leading to the formation of the different products.     

Web search and data mining of natural products and their bioactivities in PubChem

Natural products,as major resources for drug discovery historically,are gaining more attentions recently due to the advancement in genomic sequencing and other technologies,which makes them attractive and amenable to drug candidate screening.Collecting and mining the bioactivity information of natural products are extremely important for accelerating drug development process by reducing cost.Lately,a number of publicly accessible databases have been established to facilitate the access to the chemical biology data for small molecules including natural products.Thus,it is imperative for scientists in related fields to exploit these resources in order to expedite their researches on natural products as drug leads/candidates for disease treatment.PubChem,as a public database,contains large amounts of natural products associated with bioactivity data.In this review,we introduce the information system provided at PubChem,and systematically describe the applications for a set of PubChem web services for rapid data retrieval,analysis,and downloading of natural products.We hope this work can serve as a starting point for the researchers to perform data mining on natural products using PubChem.     

Further Investigation on the Rearrangement Mechanism of Reactions of 1,5-Benzothiazepines with Ethoxycarbonylcarbene

IntroductionDuring the last decade,our group has investigateda series of cycloaddition reactions of2,3-dihydro-1,5-benzothiazepines withα-carbonyl-ketenes[1,2],nitrileoxides[3,4],nitrile imines[3,4],ketenes[5—8],andcarbenes[9—11].Normal cycloadducts ca…