Environmentally Friendly Techniques and Their Comparison in the Extraction of Natural Antioxidants from Green Tea,Rosemary, Clove,and Oregano

Many current food and health trends demand the use of more ecological, sustainable, and environmentally friendly techniques for the extraction of bioactive compounds, including antioxidants. However, extraction yields and final antioxidant activities vary between sources and are highly influenced by the given extraction method and nature and ratio of the employed solvent, especially for total polyphenols, flavonoids, and anthocyanins, which are well recognized as natural antioxidants with food applications. This review focused on the most common extraction techniques and potential antioxidant activity in the food industry for various natural antioxidant sources, such as green tea, rosemary, clove, and oregano. Green extraction techniques have been proven to be far more efficient, environmentally friendly, and economical. In general, these techniques include the use of microwaves, ultrasound, high hydrostatic pressure, pulsed electric fields, enzymes, and deep eutectic solvents, among others. These extraction methods are described here, including their advantages, disadvantages, and applications.     

Green synthesis of biogenic metal nanoparticles by terrestrial and aquatic phototrophic and heterotrophic eukaryotes and biocompatible agents

The size, shape and controlled dispersity of nanoparticles play a vital role in determining the physical, chemical, optical and electronic properties attributing its applications in environmental, biotechnological and biomedical fields. Various physical and chemical processes have been exploited in the synthesis of several inorganic metal nanoparticles by wet and dry approaches viz., ultraviolet irradiation, aerosol technologies, lithography, laser ablation, ultrasonic fields, and photochemical reduction techniques. However, these methodologies remain expensive and involve the use of hazardous chemicals. Therefore, there is a growing concern for the development of alternative environment friendly and sustainable methods. Increasing awareness towards green chemistry and biological processes has led to a necessity to develop simple, cost-effective and eco-friendly procedures. Phototrophic eukaryotes such as plants, algae, and diatoms and heterotrophic human cell lines and some biocompatible agents have been reported to synthesize greener nanoparticles like cobalt, copper, silver, gold, bimetallic alloys, silica, palladium, platinum, iridium, magnetite and quantum dots. Owing to the diversity and sustainability, the use of phototrophic and heterotrophic eukaryotes and biocompatible agents for the synthesis of nanomaterials is yet to be fully explored. This review describes the recent advancements in the green synthesis and applications of metal nanoparticles by plants, aquatic autotrophs, human cell lines, biocompatible agents and biomolecules.     

Synthesis,structure, and function of internally functionalized dendrimers

The past three decades have witnessed an exponential increase in the structural diversity and applications of dendrimers, spanning across drug delivery and diagnostics, protein, and enzyme mimicry, solubility enhancement, coatings, light harvesting, and catalysis. The dendrimer community has recently focused on internally functionalized dendrimers (IFDs) owing to their advanced design and functionality. The synthesis of IFDs relies on advanced orthogonal chemistries and/or (de)protection schemes, as well as careful purification to minimize polydispersity of composition and molecular weight. The studies published on IFDs, however, lay scattered across the chemical literature, and a comprehensive presentation of structural rationale, synthetic procedures, and technologically relevant applications is missing. To address this need, this review presents a comprehensive collection and discussion of all available studies on IFDs, detailing their methods of synthesis and their structure–function correlations. The wide variety of internal functionalities, including hydroxyl, amine, carboxylic acid, allyl, alkyne, and imidazole groups, enables myriad applications in biochemistry, chemical and biomedical engineering, and material science. Particular focus is given to IFDs that are amenable to modular synthetic strategies, which promote higher synthetic yield and scalability, and therefore possess stronger translational and commercial potential. As such, this review guides research groups pursuing the difficult task of IFD rational design and synthesis providing them a concise roadmap to their mission.     

Recent development in nanomaterials fabricated paper-based colorimetric and fluorescent sensors: A review

The paper-based sensing devices have drawn a broad interest in analytical chemistry for colorimetric and fluorescent-based analysis of biological, environmental, clinical, and food samples. It is due to the simple, rapid, biodegradable, user-friendly, less expensive, and low waste generation into the environment. Here, the recent development of paper-based sensors fabricated with different noble metal nanoparticles (NPs) and semiconductor and carbon quantum dots (QDs) is demonstrated to analyze several chemical substances from various samples. User-friendly and portable recording devices such as digital cameras, smartphones, scanners, etc. along with color detecting softwares are employed to measure the color intensity of nanomaterials fabricated paper devices after the deposition of a sample solution containing various chemical substances. The advantages and disadvantages of incorporating nanomaterials in the paper substrate (direct deposition, inkjet printing, screen printing and wax printing) are illustrated. The mechanism for colorimetric, fluorescence, phosphorescence, and chemiluminescence sensing using noble metal NPs (Ag, Cu, and Au), semiconductors, and carbon QDs for the determination of metal ions, anions, pesticides, biomolecules, and other toxic chemical substances are discussed. Thus, this review article would be highly useful for scientists and researchers to design colorimetric sensors to monitor chemical toxicants in clinical, environment, foods, and many other related samples.     

生物光化学

生物光化学研究光在动植物体内所引起的生化现象。例如:经过各种不同波长的光辐照后的生命现象,生长规律,某些生理和病理过程,疾病的产生和治疗机理,细胞的辐射损伤和自然防御,以及光合色素在生物进化中的作用等。本文就光引起的现象:视觉、生物钟(光周期性)、植物的光合作用、辐射损伤及其修复、牛皮癣的治疗、新生儿黄疸病的治疗机理,以及光合色素——藻胆蛋白等七种现象,做了综述性的介绍。     

三唑类药物研究新进展

三唑类化合物作为药物广泛应用于临床,是目前药物研究开发的重点领域之一．越来越多的高活性、低毒性、不良反应少、多药耐药性小、生物利用率高、药代动力学性质好、药物靶向性强、给药方式多样化、广谱、高疗效的三唑类化合物作为候选药物或药物用于临床医治多种疾病,显示出了三唑类化合物在医药领域的巨大开发价值和潜在的宽广应用．本文结合自己的工作,参考国内外近五年文献系统地综述了三唑类化合物作为药物在整个医药领域的研究与开发近况,包括抗真菌、抗细菌、抗结核、抗癌、抗病毒、抗炎镇痛、抗惊厥等,并展望其发展趋势与前景．希望该评论有助于为高活性低毒性三唑类医药合理设计提供新思路．     

THE EFFECT OF CLAY DISPERSION ON THE CRYSTALLIZATION AND MORPHOLOGY OF POLYPROPYLENE／CLAY COMPOSITES

PP/clay composites with different dispersions, namely, exfoliated dispersion, intercalated dispersion and agglomerates and particle-like dispersion, were prepared by direct melt intercalation or compounding. The effect of clay dispersion on the crystallization and morphology of PP was investigated via PLM, SAXS and DSC. Experimental results show that exfoliated clay layers are much more efficient than intercalated clay and agglomerates of clay in serving as nucleation agent due to the nano-scale dispersion of clay, resulting in a dramatic decrease in crystal size (lamellar thickness and spherulites) and an increase of crystallization temperature and crystallization rate. On the other hand, a decrease of melting temperature and crystallinity was also observed in PP/clay composites with exfoliated dispersion, due to the strong interaction between PP and clay. Compared with exfoliated clay layers, the intercalated clay layers have a less important effect on the crystallization and crystal morphology. No effect is seen for samples with agglomerates and particle-like dispersion, in regard to melting temperature, crystallization temperature, crystal thickness and crystallinity.     

Purification and properties of three cellobiases from Aspergillus niger A20

Three cellobiases, here called cellobiase A, B, and C, from the culture filtrate of Aspergillus niger A20, were purified by precipitation with ammonium sulphate, gel filtration through Sephadex G-75, and column chromatography of DEAE-cellulose. The purified enzymes were homogeneous on polyacrylamide disk electrophoresis. The mol wt of the purified enzymes were estimated by SDS-gelelectrophoresis to be 88,000, 80,000, and 71,000 for cellobiases A, B, and C, respectively. The enzymes were active at pH 4.5 and 55–60°C. The pattern of their aminoacid compositions showed high contents of aspartic acid, glutamic acid, threonine, serine, and glycine. The apparent K_m values for cellobiose were 0.9, 1.63, and 1.0 mM for cellobiases A, B, and C, respectively. Calcium ions stimulated cellobiases B and C, and Co²⁺ and Mg²⁺ ions stimulated cell obiase A. The purified enzymes hydrolyzed cellobiose and aryl-β-d-glucosides, but they had no action on sucrose, maltose, and cellulose. The three cellobiases catalyzed transglycosylate reaction, and the major product formed from cellobiose was tetramer of glucose.     

石墨烯纤维：制备、性能与应用

石墨烯纤维是一种由石墨烯片层紧密有序排列而成的一维宏观组装材料。通过合理的结构设计和可控制备,石墨烯纤维能够将石墨烯在微观尺度的优异性能有效传递至宏观尺度,展现出优异的力学、电学、热学等性能,从而应用于功能织物、传感、能源等领域。目前,石墨烯纤维主要通过湿法纺丝、限域水热组装等方法制备得到,其性能可以通过对材料体系和制备工艺的优化而进一步提升。本文首先介绍了石墨烯纤维的制备方法,然后详细阐述了石墨烯纤维的性能,讨论了其性能提升策略,并总结了石墨烯纤维的应用,最后对石墨烯纤维的未来发展、挑战和前景进行了展望。     

Tautomeric and conformational isomerism of natural hydroxyanthraquinones

Natural 1,5-di-, 1,4,5-tri-, and 1,4,5,8-tetrahydroxyanthraquinones and their anions and metal complexes were shown to be equilibrium mixtures of tautomers and conformers using quantum-chemical and correlation analysis of elecronic absorption spectra. Solvent effects, ionization, complexation, and the introduction and substitution of substituents were accompanied by shifts of tautomeric and conformational equilibria that determine the color of the compounds. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 224–229, May–June, 2006.