Xanthone derivatives from Cratoxylum cochinchinense roots

Two xanthones and two caged-prenylated xanthones, named cochinchinones A-D, respectively, and a synthetically known caged-prenylated xanthone, together with seven known compounds were isolated from the roots of Cratoxylum cochinchinense (Lour.) Blume. Their structures were assigned on the basis of analyses of spectroscopic data. Some of the compounds exhibited effective antioxidative properties.     

Synthesis, structure, and reactivity of fluorous phosphorus/carbon/phosphorus pincer complexes derived from P(CH2)5P backbones

Reactions of the diphosphine H₂P(CH₂)₅PH₂ and fluorous alkenes H₂CCHR_fn (excess; R_fn = (CF₂)_n−1CF₃; n = a, 6; b, 8; c, 10) at 60 °C in the presence of AIBN give the precursors (R_fnCH₂CH₂)₂P(CH₂)₅P(CH₂CH₂R_fn)₂ (2a-c; 68-74%). These react with Pd(O₂CCF₃)₂ in CF₃C₆F₅ at 80 °C to give the title complexes (5a-c, 51-18%). Addition of LiCl to 5b gives (6b, 97%); subsequent reaction with MeLi affords the corresponding methyl complex (97%). A solvate of 6b is crystallographically characterized. The structure exhibits CH₂CH₂R_f8 groups with nearly anti C-C-C-C conformations, extending in parallel above and below the palladium square plane to create fluorous lattice domains. Reactions of 2b and other metal complexes are described; in the cases of (PhCN)₂PdCl₂ or (COD)₂PtCl₂ (CF₃C₆H₅, room temperature), bimetallic species in which two MCl₂ moieties are bridged by two diphosphines appear to form. The CF₃C₆F₁₁/toluene partition coefficients of 2a-c and 5a-c establish high fluorophilicities; despite the lower fluorine weight%, those of 5a-c are slightly greater ((97.4-99.7):(2.6-0.3) versus (95.3-99.3):(4.7-0.7)).     

Chlorodifluoromethyl-substituted monosaccharide derivatives--radical activation of the carbon-chlorine-bond

The dithionite-mediated addition of BrCF(2)Cl to 3,4-di-O-pivaloyl-D-xylal (1) generated preferably 1-CF(2)Cl-substituted products, that is, (2-bromo-2-deoxy-3,4-di-O-pivaloyl-beta-D-xylopyranosyl)-chlorodifluoromethane and (2-deoxy-3,4-di-O-pivaloyl-beta-D-threo-pentopyranosyl)-chlorodifluoromethane. Selected chlorodifluoromethyl-substituted monosaccharide derivatives were hydrodechlorinated or alkylated at the CF(2)Cl-group using tin reagents under radical reaction conditions. Thus, hydrodechlorinations of (2,3,4-tri-O-acetyl-6-deoxy-alpha-L-galactopyranosyl)-chlorodifluoromethane and of methyl 3,4-di-O-acetyl-2-C-chlorodifluoromethyl-2,6-dideoxy-alpha/beta-L-glucopyranoside are reported using tri-n-butyltin hydride initiated by AIBN. UV-initiated allylations are reported for reactions of (2-deoxy-3,4-di-O-pivaloyl-beta-D-threo-pentopyranosyl)-chlorodifluoromethane, (2,3,4-tri-O-acetyl-6-deoxy-alpha-L-galactopyranosyl)-chlorodifluoromethane, 1,3,4,6-tetra-O-acetyl-2-C-chlorodifluoromethyl-2-deoxy-alpha-D-glucopyranose, 1,3,4,6-tetra-O-acetyl-2-C-chlorodifluoromethyl-2-deoxy-alpha-D-mannopyranose and methyl 3,4-di-O-acetyl-2-C-chlorodifluoromethyl-2-deoxy-alpha/beta-D-rabinopyranoside with allyltri-n-butyltin.     

Environment of TyrZ in photosystem II from Thermosynechococcus elongatus in which PsbA2 is the D1 protein

The main cofactors that determine the photosystem II (PSII) oxygen evolution activity are borne by the D1 and D2 subunits. In the cyanobacterium Thermosynechococcus elongatus, there are three psbA genes coding for D1. Among the 344 residues constituting D1, there are 21 substitutions between PsbA1 and PsbA3, 31 between PsbA1 and PsbA2, and 27 between PsbA2 and PsbA3. Here, we present the first study of PsbA2-PSII. Using EPR and UV-visible time-resolved absorption spectroscopy, we show that: (i) the time-resolved EPR spectrum of Tyr_Z^• in the (S₃Tyr_Z^•)′ is slightly modified; (ii) the split EPR signal arising from Tyr_Z^• in the (S₂Tyr_Z^•)′ state induced by near-infrared illumination at 4.2 K of the S₃Tyr_Z state is significantly modified; and (iii) the slow phases of P₆₈₀^+⋅ reduction by Tyr_Z are slowed down from the hundreds of μs time range to the ms time range, whereas both the S₁Tyr_Z^• → S₂Tyr_Z and the S₃Tyr_Z^• → S₀Tyr_Z + O₂ transition kinetics remained similar to those in PsbA(1/3)-PSII. These results show that the geometry of the Tyr_Z phenol and its environment, likely the Tyr-O···H···Nϵ-His bonding, are modified in PsbA2-PSII when compared with PsbA(1/3)-PSII. They also point to the dynamics of the proton-coupled electron transfer processes associated with the oxidation of Tyr_Z being affected. From sequence comparison, we propose that the C144P and P173M substitutions in PsbA2-PSII versus PsbA(1/3)-PSII, respectively located upstream of the α-helix bearing Tyr_Z and between the two α-helices bearing Tyr_Z and its hydrogen-bonded partner, His-190, are responsible for these changes.     

Antioxidant activity of polyphenolic extracts of Ichnocarpus frutescens

In the present study antioxidant activities by (1,1-diphenyl-2-picrylhydrazyl radical (DPPH), hydrogen peroxide, hydroxyl radical inhibition, hemolysis by hydrogen peroxide assay, reducing power and total antioxidant activities of polyphenolic extract of Ichnocarpus frutescens leaves were investigated. The flavonoids and total polyphenolic contents of the extract were also determined using standard methods. Phytochemical analyses revealed the presence of flavonoids, polyphenols, anthocyanins and simple phenolic acids. The results of antioxidant activities of polyphenol extract obtained by different in vitro methods were varied depending on the method used. Nevertheless, polyphenol extract showed significant inhibitory activities in all in vitro reactive oxygen species scavenging, might be attributed due to the high level of polyphenolic compound. Also, these various antioxidant activities were compared to α-tocopherol and l-ascorbic acid as reference antioxidant compounds. These findings provide evidence that the polyphenolic extract of I. frutescens is a natural source of antioxidant against oxidative damage.     

Cytotoxicity and antioxidant activity of 5-(2,4-dimethylbenzyl)pyrrolidin-2-one extracted from marine Streptomyces VITSVK5 spp.

The aim of the present study was to evaluate the cytotoxicity and antioxidant activity of 5-(2,4-dimethylbenzyl)pyrrolidin-2-one (DMBPO) extracted from marine Streptomyces VITSVK5 spp. The strain was isolated from sediment samples collected at the Marakkanam coast of Bay of Bengal, India. Systematic screening of isolates for anti-Aspergillus activity resulted in the identification of Streptomyces species designated as Streptomyces VITSVK5 spp. Bioactivity guided extraction and purification yielded a compound 5-(2,4-dimethylbenzyl)pyrrolidin-2-one (DMBPO) and was tested for cytotoxicity and antioxidant activity. The structure of the extracted compound was established by spectroscopic studies and identified as 5-(2,4-dimethylbenzyl)pyrrolidin-2-one (DMBPO). DMBPO exhibited cytotoxic activity on HEP 2 and Hep G2 cell lines with the IC₅₀ value of 2.8 μg/ml and 8.3 μg/ml, respectively, as compared to Vero cell line (22.6). DMBPO showed the hemolytic EC₅₀ value of 288 μg/ml on human erythrocytes. DMBPO treatment showed fewer (31.7%) aberrations, gaps and chromatid breaks as compared to untreated controls (27.8%) of human chromosomes. DMBPO also exhibited significant (44.13% at 5 μg/ml DMBPO) DPPH radical scavenging activity and total antioxidant activity (50.10% at 5 μg/ml DMBPO). The results of this study showed that DMBPO is cytotoxic to cancer cells and possesses antioxidant property.     

中下段胆管癌的预后影响因素分析*

目的:探讨中下段胆管癌的预后影响因素。方法:对79例中下段胆管癌患者的临床资料进行回顾性分析,采用Kaplan-Meier分析对确定的单因素进行生存率的描述,用Cox回归进行多因素分析,采用log-rank法对单因素进行生存分析评价。结果:79例患者1、3、5年生存率分别为70.2%,36.2%,19.1%,中位生存时间为19.8个月。行根治性手术患者1年、3年、5年生存率分别为87.9%、45.5%和24.2%,分别显著高于姑息性手术患者1年、3年、5年生存率(28.9%、14.3%和7.1%);行根治性手术患者的中位生存时间为34.5个月,较姑息性手术患者显著延长(8个月),根治术与姑息性手术1、3、5年生存率及中位生存时间比较四项均P<0.01,差异具有统计学意义。单因素分析显示肿瘤病理分化,慢性病史,淋巴结转移为影响中下段胆管癌预后的因素。多因素分析显示慢性病史、手术切缘、肿瘤病理分化程度是影响中下段胆管癌预后的独立危险因素。结论:慢性病史、手术切缘、肿瘤病理分化程度为中、下段胆管癌行切除术后预后的独立危险因素,根治性手术可提高中、下段胆管癌患者的生存率和延长其生存时间。     

Synthesis of new N-isobutyryl-L-cysteine/MEA conjugates: evaluation of their free radical-scavenging activities and anti-HIV properties in human macrophages

Four novel N-isobutyryl-l-cysteine/2-mercaptoethylamine (MEA, cysteamine) conjugates have been designed and synthesized. The antioxidant activities of these new series were evaluated by three different free radical scavenging methods (DPPH test, ABTS test, and deoxyribose assay) and their metal binding capacity was evaluated by the ethidium bromide fluorescence binding assay. These results were compared with those obtained with their pro-GSH acetyl analogues recently developed in our laboratory. We observed that most of these compounds exhibit free radical-scavenging activities similar to those of Trolox, but always superior than NAC. While none of these new derivatives had pro-GSH activities, they displayed anti-HIV properties in human monocyte-derived macrophages infected in vitro. The present study demonstrates that these new N-isobutyryl derivatives, which are expected to have a greater bioavailability than their acetyl analogues, may have useful applications in HIV infection in respect to their antioxidant and anti-HIV activities.     

Radical graft functional modification of cellulose with allyl monomers: Chemistry and structure characterization

Cotton cellulose was successfully functionalized via a free radical graft polymerization process. Potassium persulfate served as an effective water soluble radical initiator to generate cellulosic radicals. The polymeric radicals could react with allyl monomers such as allyl-dimethylhydantion (ADMH) to form surface grafted cellulose. The reaction sites generated by potassium persulfate were probably at carbon 3 and 4 in glucose ring via oxidative hydrogen abstraction. The cellulosic radicals can initiate grafting polymerization of ADMH with a maximum polymerization degree of about 12 based on LC–MS results. The radical graft polymerization mechanisms were proposed based on LC–ESI/MS analysis. The ideal covalent bonding between cellulose and poly (allyl-dimethylhydantion) (PADMH) ensured permanent graft of the monomers on cotton and durability of the expected functions on the treated cotton.     

Antioxidant and radical scavenging properties of curcumin

Curcumin (diferuoyl methane) is a phenolic compound and a major component of Curcuma longa L. In the present paper, we determined the antioxidant activity of curcumin by employing various in vitro antioxidant assays such as 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH*) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, N,N-dimethyl-p-phenylenediamine dihydrochloride (DMPD) radical scavenging activity, total antioxidant activity determination by ferric thiocyanate, total reducing ability determination by the Fe(3+)-Fe(2+) transformation method, superoxide anion radical scavenging by the riboflavin/methionine/illuminate system, hydrogen peroxide scavenging and ferrous ions (Fe(2+)) chelating activities. Curcumin inhibited 97.3% lipid peroxidation of linoleic acid emulsion at 15 microg/mL concentration (20 mM). On the other hand, butylated hydroxyanisole (BHA, 123 mM), butylated hydroxytoluene (BHT, 102 mM), alpha-tocopherol (51 mM) and trolox (90 mM) as standard antioxidants indicated inhibition of 95.4, 99.7, 84.6 and 95.6% on peroxidation of linoleic acid emulsion at 45 microg/mL concentration, respectively. In addition, curcumin had an effective DPPH* scavenging, ABTS*(+) scavenging, DMPD*(+) scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe(3+)) reducing power and ferrous ions (Fe(2+)) chelating activities. Also, BHA, BHT, alpha-tocopherol and trolox, were used as the reference antioxidant and radical scavenger compounds. According to the present study, curcumin can be used in the pharmacological and food industry because of these properties.