Comparative Analysis of the Antioxidant and Free-Radical Scavenging Activities of Different Water-Soluble Extracts of Green, Black and Oolong Tea Samples

Extracts of 40 green, black or oolong high quality tea samples from China, Japan or India among others, have been prepared according to the manufacturer instructions and assayed for total polyphenols content using the Folin-Ciocalteu phenol reagent. In addition, the antioxidant activity was assessed by the CUPRAC method and the free-radical scavenging activity was determined using the antioxidant-promoting decay of the stable free-radical DPPH. Caffeine and the most important catechins were identified using RP-HPLC previously validated method. Results from this study suggest that teas, even though they content similar amounts of caffeine, differ considerably in polyphenolic content and therefore in antioxidant and free-radical scavenging activities, depending on the part of the plant used and the process applied to the material for the preparation of the final tea presentation. Correlations among Folin-Ciocalteau’s reactivity of tea samples, the neocuproine reactivity, the DPPH decolourization and the HPLC analysis suggest that the antioxidant activity is due essentially to polyphenolic compounds present in teas, mainly EGCG. The best extraction method of tea powder was the one indicated by dealers. In general, the richest samples belong to green teas and the poorest samples belong to the black teas.

Nonisothermal Kinetics of Free-Radical Polymerization of 2,2-Dinitropropyl Methacrylate

The 2,2-dinitropropyl methacrylate（DNPMA） was synthesized by esterification of α-methacrylic acid with 2,2-dinitropropanol.The free-radical bulk polymerization of DNPMA in the presence of 2,2-azobisisobutyronitrile（AIBN） was investigated by differential scanning calorimetry（DSC） in the nonisothermal mode.Kissinger,Ozawa and Barrett methods were applied to determine the activation energy（Ea） and the reaction order of the free-radical polymerization.The results showed that the temperature of exothermic polymerization peaks increased with increasing heating rate.With increasing the molar ratio of monomer/initiator and the heating rate,the reaction order of nonisothermal polymerization was approximately equal to 1.The average Ea value from Kissinger and Ozawa methods（77.74±1.07 kJ/mol） was smaller than the value from the Barrett method（Ea=102.36 kJ/mol）.

The Study of Influence of Silica and Polyethilene Glycols Organic-Inorganic Compounds on Free-Radical Processes in Vitro

In this study investigation of influence of hybrid nanosilica-polyethylene glycols materials (molecular weight 1500, 6000 and 15000), prepared by sol-gel synthesis, on lipid peroxidation and antioxidant activity of human serum in vitro was performed. Methods included chemiluminescence analysis and quantitative malonic dialdehyde estimation. It was revealed that nanosilica-PEG materials with different molecular weight had certain biological activity. Powders of SiO2-PEG 1500 and SiO2-PEG 6000 manifest prooxidant effects, whereas mesoporous (calcine) powders produced antioxidant effects in blood serum in vitro.

Protective role of buffalo pineal proteins on arsenic-induced oxidative stress in blood and kidney of rats

Objective: Exposure to various toxic metals has become an increasingly recognized source of ill- ness in human and animals, worldwide. Arsenic (As) and its compounds cause adverse health effects in animals and humans. Recently, it has been suggested that the pineal gland may also have antioxidants role due to secretary product other than melatonin. With keeping this view, pre-sent investigation tested effect of buffalo (Bubalus bubalis) pineal proteins (PP) on arsenic-induced oxidative stress in RBCs (Red blood cells) and kidney of rats. Methods: Eighteen adult female Wistar rats were grouped into group-I (Control), group-II (Arsenic control), and group-III (Arsenic + Pineal proteins). Experimental rats were given 100 ppm arsenic (p.o.) for 4 weeks alone or along with pineal proteins at a dose of 100 μg/kg body weight (i.p.). Results: Interestingly, arsenic ex-posure led to the stimulation of kidney catalase (CAT) activity, but inhibition of RBCs CAT activ-ity and significantly (P<0.05) increased the RBCs and kidney lipid peroxidation level (LPO). How-ever, arsenic treatment caused depletion of glu- tathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) in kidney tissues. In RBCs, only GR and CAT activity were significantly (P<0.05) declined. These changes were significantly (P<0.05) reversed by PP treatment in arsenic exposed animals. Conclusion: Therefore, present study indicated the significant protecting effect of buf-falo (Bubalus bubalis) PP against arsenic in-duced-oxidative stress through antioxidant de-fense systems in rats.

Crystal Structure, Synthesis and Biological Activity of Ether and Ester <i>Trans</i>-Ferulic Acid Derivatives

The structures of methoxymethyl (E)-3-(4-hydroxy-3-methoxyphenyl)acrylate, 2;(E)-3-(3-methoxy-4-(methoxymethoxy)phenyl)acrylic acid, 3;methyl (E)- 3-(4-(benzyloxy)-3-methoxyphenyl)acrylate, 4;benzyl (E)-3-(4-(benzyloxy)- 3-methoxyphenyl)acrylate, 6;and (E)-3-(4-(benzyloxy)-3-methoxyphenyl)- acrylic acid, 7;were established by spectroscopic and X-ray diffraction studies. Structure 2 is a new com-pound. Compounds with free phenolic hydroxyls v.gr. methyl (E)-3-(4-hydroxy-3-methoxyphenyl)acrylate 1, 2 and ben-zyl(E)-3-(4-hydroxy-3-methoxyphenyl)acrylate 5, showed scavenging free- radical and antioxidant activity while moderate scavenging free-radical was observed in compound 3. Moderate inhibition of lipid peroxidation was observed for 7. Compound 5 exerted significant inhibition of cell growth in PC-3, K562 tumor cell lines and 4 exhibited the largest cytotoxic effect upon the K562 cell line.

Herbal antioxidant in clinical practice:A review

Antioxidant-the word itself is magic.Using the antioxidant concept as a spearhead in proposed mechanisms for staving off so-called"free-radical"reactions,the rush is on to mine claims for the latest and most effective combination of free-radical scavenging compounds.We must acknowledge that such"radicals"have definitively been shown to damage all biochemical components such as DNA/HNA,carbohydrates,unsaturated lipids,proteins,and micronutrients such as carotenoids(alpha and beta carotene,lycopene),vitamins A,B_6,B_(12),and folate.Defense strategies against such aggressive radical species include enzymes,antioxidants that occur naturally in the body(glutathione,uric acid,ubiquinol-10,and others)and radical scavenging nutrients,such as vitamins A,C,and E,and carotenoids.This paper will present a brief discussion of some well-and little-known herbs that may add to the optimization of antioxidant status and therefore offer added preventive values for overall health.It is important to state at the outset that antioxidants vary widely in their free-radical quenching effects and each may be individually attracted to specific cell sites.Further evidence of the specialized nature of the carotenoids is demonstrated by the appearance of two carotenoids in the macula region of the retina where beta-carotene is totally

Selenylation Modification of Degraded Polysaccharide from Enteromorpha prolifera and Its Biological Activities

Polysaccharide extracted from Enteromorpha prolifera possessed excellent biological activities,but its molecular weight was greatly high which influenced the activity.Organic Se had higher biological activities and was safer than inorganic Se species.In the present study,Enteromorpha polysaccharide was degraded to low molecular weight by free-radical degradation method of H_2O_2 and ascorbic acid.By single factor and orthogonal experiments,the optimal degradation conditions were reaction time of 2 h,reaction temperature of 50℃,H_2O_2/ascorbic acid(n/n=1:1)concentration of 15 mmol L^(-1),and solid-liquid ratio of 1:50(g mL^(-1)).Then,the degraded polysaccharide was chemically modified to obtain its selenide derivatives by nitric acid-sodium selenite method.The selenium content was 1137.29μg g^(-1),while the content of sulfate radical had no change.IR spectra indicated that the selenite ester group was formed.Degraded polysaccharide selenide was characterized and evaluated for antioxidant,antifungal and antibacterial activities.The results showed that degraded polysaccharide selenide had strong capacity of scavenging DPPH and·OH free radical.It had significant antibacterial properties for Escherichia coli,Bacillus subtilis and Salmonella spp.,and it also had significant antifungal properties for Apple anthrax.The result ascertained degradation and selenylation modification did not change the main structure of polysaccharides.It was possible that free-radical degradation was an effective way for enhancing antioxidant activity to decrease molecular weight of polysaccharides.

Anti-inflammatory and antioxidant activities of ethanolic extract of aerial parts of Vernonia patula(Dryand.)Merr.

Objective:To investigate the inflammatory and antioxidant activities of ethanolie extract of aerial part of Vernonia patula(Dryand.)Merr(EAV).Methods:The anti-inflammatory activity of EAV was studied using carrageenan and histamine-induced rat paw edema test at different doses(100.200 and 400 mg/kg body weight).DPPH free radical scavenging,nitric oxide scavenging,reducing power and Fe^(2+)ion chelating ability were used for determining antioxidant activities.Results:The EAV,at the dose of 400 mg/kg,showed a significant anti-inflammatory activity(P<0.01)both in the carrageenan and histamine-induced oedema test models in rats,showing62.86%and 64.42%reduction in the paw volume comparable to that produced by the standard drug indomethacin(67.26%and 66.01%)at 5 h respectively.In DPPH free radical scavenging test,IC_(50)value for EAV was found fairly significant 36.59μg/mL when compared to the IC_(50)value of the reference standards ascorbic acid 8.97μg/mL.The IC_(50)values of the extract and ascorbic acid were 47.72 and 12.39μg/mL,respectively in nitric oxide scavenging assay.The IC_(50)value of the EAV(33.59μg/mL)as percentage of Fe^(2+)ion chelating ability was also found significant compared to that of EDTA(9.16μg/mL).The maximum absorbance for reducing power assay was found to be1.928 at 100μg/mL when compared to 2.449 for standard ascorbic acid.The total phenolic content was 198.81 mg/g of gallic acid equivalent.Acute toxicity test showed that the plant might be safe for pharmacological uses up to a dose level of 3200 mg/kg of body weight in rats.Conclusions:Therefore,the obtained results suggest the acute anti-inflammatory and antioxidant activities of the EAV and thus provide the scientific basis for the traditional uses of this plant part as a remedy for inflammations.

Cytoprotective effects of quercetin and its sugar-containing natural congeners in cultured HEK293 cells injured by anoxia/hypoglycemia and the structure-effect relationship thereto

Objective To comparatively study anti-free radical and cytoprotective effects of quercetin(Q)and its monoglucoside isoquercetin(I),diglucoside rutin(R),which differs only in glycosyl-substitution at C-3 position of the molecules,using anoxia/hypoglycemia-induced cell injury model and thereby to explore the structure-effect relationship thereto.Methods The cell injury model was established by HEK293 cells cultured in vitro with Na2S2O3 plus sugar-free Earle's fluid as incubation medium;Cell survival rate(CSR),total antioxidant capacity(TAC),SOD and LDH levels were determined;The effect intensity of the 3 flavonoids were compared by means of IC50,the concentration required to achieve 50% inhibition of the changes in the above indices in injured cells.Results Q,I and R all concentration-dependently elevated CSR,TAC and SOD,and reduced LDH level;the all of IC50s for the above indices were ranked in order of IC50,Q<IC50,I<IC50,R,namely,the effect intensity should be Q>I>R.Conclusions The 3 structurally similar flavoloids all have significant and concentration-dependent anti-free radical and cyto-protective effects with the intensity being in order of aglycone>monoglucoside>diglucoside;the substitution of-OH by sugar group at C-3 position of flavoloids and increase in the sugar-substituent number are associated with the effect intensity reduced;namely,the intensity of these effects of flavonoids is negatively related the substutution by sugar group at C-3 position.

SYNTHESIS AND POLYMERIZATION OF OLIGO (OXYETHYLENE) MACROMONOMER

This paper reports the synthesis of methoxyoligo (oxyethylene) methacrylate (MEO_n , n is the repeating unit number of (CH_2CH_2O) in the macromonomer), and its polymerization in different solvents. MEO_n is prepared through such two independent reactions as (1) anionic polymerization of oxirane initiated by potassium alkoxide and (2) end-capping of methoxy oligo(oxyethylene) by methacrylic group. The n value can be conveniently controlled over the range of 5 ～ 30 by varying the molar ratio of oxirane to initiator and the molecular weight distribution of MEO_n be narrowed by increasing reaction time only in step (1). MEO_n thus obtained shows a rapid polymerization in water and benzene respectively, and both give water-soluble polymers as long as suitable conditions are used.

SOME REMARKS ON THE POLYMERIZATION REACTION ENGINEERING

In this paper,we overview beifely some of our key projects that had contridubted to modifyprevious author’s conclusions and put forward new viewpoints that are being underinvestigation.The novel ideas worth mentioning are the calculation of the sequence distributionon the copolymerization with a new version of probability suggested,the characterization of stepgrowth polymerization that indicates the MDW may not be continuous in theory,and after all,the Nylon 6 polymerization engineering exploitation where the concept of water activity is usedin place of concentration so as to extend the applicability’of the kinetic model proposed previous-ly.

Structural and Functional Tailoring of Melanin-Like Polydopamine Radical Scavengers

Melanin is a ubiquitous but poorly understood polymeric,dark brown to black pigment biomaterial found both in nature and by organic synthesis.Its structural heterogeneity and disordered covalent/noncovalent interactions make it a grand challenge to tune and improve the physical and biological properties of both melanin sources.Herein,we report a facile one-pot fabrication approach for synthetic melanins with controlled size and composition via copolymerization of dopamine and basic amino acid such as arginine in an aqueous solution.The resulting arginine-doped polydopamine melanin-like nanoparticles possess less ordered nonplanar microstructures within the particles,whereas the conventional polydopamine-based melanins contain a variety of compactπ-stacked microstructures.The assembly of these distinct polymeric microstructures could lead the preceding ones for greater accessibility to free radicals,with resultant stronger free-radical scavenging effect,and thus,exhibit superior antioxidant performance toward cellular oxidative stress.This work has inspired us to continue to fabricate new synthetic melanin pigments with tunable and improved functions by rational structural tailoring.

HMO TREATMENT OF UNBRANCHED ALKANES

It is well known that HMO theory is successful in understanding the chemical properties of conjugated molecules. By a similar way, some authors has studied nonconjugated molecules, and some useful results have been obtained. In this note, after a careful theoretical analysis, π orbital (anti-symmetrical with respect to the carbon frame plane )HMO formulae which are suitable to unbranched alkanes are obtained.

Facile tuning of hydrogel properties by manipulating cationic-aromatic monomer sequences

Copolymer hydrogels formed from cationic and aromatic monomers with identical monomer compositions but different average sequences were synthesized by free-radical copolymerization in various solvents.We found that hydrogels with one-componentrich segments are mechanically stronger than those with adjacent-rich monomer sequences in water,while hydrogels with a rich cation-πadjacent sequence showed excellent mechanical strength and underwater adhesion in saltwater(0.7 M Na Cl).The molecular mechanisms for these behaviors are discussed in terms of polymer structures.This work reveals the importance of monomeric sequences in determining hydrogel properties and provides a facile approach to develop hydrogels with different properties but the same monomer composition.

超稳定的碲掺杂碳量子点在细胞保护和光动力学治疗中的应用

由于活性氧(ROS)在人体新陈代谢中起着重要作用,调节细胞内ROS浓度维持水平是不容忽视的,因此开发能够控制活性氧含量的纳米试剂是非常有意义的.本文采用简单有效的水热法制备了碲掺杂碳量子点(Te-CDs).该量子点水溶性好、稳定性高,具有生物相容性,在溶液水平能够消耗H2O2,在光照下能够产生·OH.因此该碳量子点可作为抗氧化剂应用于细胞保护中,也可作为光敏剂应用于光动力治疗,这双重作用在细胞中均取得了良好的效果,并有望与其他药物共同用于多模态肿瘤治疗.

Phenolic compounds from the aqueous extract of Acacia catechu

From the aqueous extract of Acacia catechu,two new phenolic compounds（3R,4R）-3-（3,4-dihydroxyphenyl）-4-hydroxycy-clohexanone （1） and（4R）-5-（1-（3,4-dihydrophenyl）-3-oxobutyl）-dihydrofuran-2（3H）-one（2） were obtained.Their structures were determined on the basis of spectroscopic analysis.Free-radical scavenging activities of them were evaluated.