稀土金属氧化物表面活性氧以及甲烷氧化偶联反应的研究

天然气中含有极其丰富的甲烷，目前绝大部分都被当作燃料烧掉了。这就给我们化学工作者提出一个新的课题，即天然气的化学利用自从八十年代初期以来，许多化学工作者进行了甲烷氧化偶联制乙烷、乙烯的研究，其特点是可以不经过合成气的过程，由甲烷直接转化成乙烷和乙烯。本文研究了Li/La_2O_3催化剂对甲烷氧化偶联反应的催化活性。首先考察了焙烧温度对催化性能的影响。其中6wt%Li/La_2O_3催化剂分别在350 ℃, 850 ℃, 950 ℃焙烧，发现低温反应时，焙烧温度较低的催化剂具有较高的C_2化合物产率，高温反应时也具有类似的结果。780 ℃反应时，350 ℃焙烧的催化剂具有最高的C_2化合物产率12%（CH_4:O_2 = 2）和14%（CH_4:O_2 = 3）。X-衍射结果表明：350 ℃焙烧的催化剂是由多种物相组成的不稳定态。在相同的反应条件下，比较了850 ℃焙烧的6wt%Li/La_2O_3和3wt%Li/La_2O_3催化剂（CO_2中制），发现在所有的反应温度范围3wt%Li/La_2O_3（CO_2中制）催化剂C_2化合物的产率都比6wt%Li/La_2O_3高的多。表明CO_2对催化活性有着一定的影响。反应混合物中CH_4和O_2的配比对催化反应影响的研究，发现只有当CH_4:O_2 = 3时，甲烷的转化率较高，C_2化合物的选择性最好，C_1化合物的选择性最低。研究了催化剂中Li含量对催化性能的影响，发现加Li的催化剂C_2化合物的选择性和产率都比La_2O_3高，在所研究的范围内（Li含量0% ～ 3.2%），0.6wt%Li/La_2O_3催化剂C_2化合物产率高达17%，C_2化合物的选择性几乎不变（68%）。La_2O_3选择性只有40%，可见Li/La_2O_3催化剂对纯La_2O_3具有高的催化活性。为了进一步探讨催化反应机理，研究了Li/La_2O_3催化剂表面氧的形态，用ESR方法检测到O_2~-的存在，其g值为g_(22) = 2.031，g_(yy) = 2.000, g_(xx) = 1.995。这种O_2~-离子室温不稳定。我认为O_2~-在高温时能与CH_4发生反应，其反应机理如下：O_2(gas) <=> O_2(ads) →+e O_2~- → +e → 2O~- → +2e 2O~(2-) O~- + CH_4 → CH_3 + OH~- 2CH_3 → C_2H_6 C_2H_6 + O~- → C_2H_5 + OH~- C_2H_5 + O~(2-) → C_2H_5O~- + e C_2H_5O~- → C_2H_4 + OH~- CH_3 + O~(2-) → OCH_3~- → CO, CO_2 CH_3 + O_2 → CH_3O_2 → CO, CO_2 研究了CH_4在La_2O_3和Li/La_2O_3催化剂上吸附后的低温（77K）程脱发现低温（77K）时，CH_4在La_2O_3上发生了化学吸附，产生了CO和CO_2即La_2O_3催化剂77K时可以活化甲烷，但有利于甲烷完全氧化。77K时，CH_4在Li/La_2O_3催化剂上也发生了化学吸附，产物除CO和CO_2外，还有部分乙烷生成。可见与La_2O_3相比Li/La_2O_3催化剂77K有利于甲烷选择性氧化。在Sm_2O_3和Eu_2O_3表面活性氧检测方面也作了大量的工作用急冷和慢慢冷却的方法，在Sm_2O_3和Eu_2O_3表面都没有检测到表面氧。

气相中双电荷离子解离反应的研究

本论文主要利用质量分析离子动能谱（MIKES）和双电荷离子质谱（2E谱）分别研究了乙烯和乙烷产生的[C_2H_4]~(2+),苯甲酰氨产生的[C_7H_7NO]~(2+)、[C_7H_5O]~(2+)、[C_6H_7N]~(2+)，三种苯二胺异构体产生的C_6H_8N_2]~(2+)、[C_6H_7N_2]~(2+)、[C_6H_6N_2]~(2+)，对称苯肼和联苯胺[~(13)CC_(11)H_(12)N_2]~(2+)、[C_(12)H_(12)N_2]~(2+)、[C_(12)H_(11)N_2]~(2+)、[C_(12)H_(10)N_2]~(2+)、[C_(12)H_9N_2]~(2+)，四种氯代甲苯产生的[C_7H_7Cl]~(2+)、[C_YH_6Cl]~(2+)、[C_7H_6Cl]~(2+)，四种溴代中甲苯产生的[C_7H_7Br]~(2+)，联苯衍生物产生的[C_(12)H_(10)]~(2+)、[C_(12)H_8]~(2+)、[C_(18)H_(14)]~(2+)、[C_(12)H_(10)O]~(2+)、[C_(12)H_(11)N]~(2+)、[C_(12)H_9F]~(2+)、[C_(12)H_9Br]~(2+)和[C_(12)H_9NO_2]~(2+)等48种双电荷离子的单分子中性丢失解离、单分子电荷分离、CID中性丢失解离、CID电荷分离和电子捕获诱导解离（ECID）反应，以及所有体系的单电荷分子离子的CID和[C_7H_7Br]~+的电荷剥离谱。用量子力学半经验方法（MNDO）计算了[C_(12)H_8]~(2+)离子中的电荷定位。主要讨论的问题有：重排反应：1）异构化反应。二取代苯类化合物单双电荷离子都可发生这类重排，生成同一的七元环或直链结构，使它们的MIKES完全一致。2）H重排。除了C_2H_4~(2+)外，其它离子的大部分反应都涉及到H的重排。MNDO计算表明联苯或其取代物的同一个苯环中丢失不同位置的H生成的离子的能量差值很小，说明同一个苯环上的H是很难区分的。3）取代基重排。不但苯环上的取代基会发生重排，侧链上的取代基也会发生重排，如苯甲酰胺亚稳双电荷离子中酰胺基上的NH_2可以重排到苯环上。4）苯环重排。对称苯肼单双电荷 离子可发生类似溶液中联苯胺重排的反应，两个苯环联到一起。电荷分离过度态和其中的电荷定位：本论文通过电荷分离过度态中是电荷间距，讨论了亚稳双电荷离子各种可能的过度态结构，同一种双电荷离子往往可通过不同的过度态解离。“偶电子规则”：偶电子离子和奇电子离子的中性失H反应表现出完全不同的规律。例如苯二胺分子离子单分子失H可分别丢失1、2、4个H，CID失H可分别丢失1、2、4、6、8个H，而[C_6H_7N_2]~(2+)则没有这种选择性。但对称苯肼、联苯胺和取代联苯双电荷离子的解离不出现这种现象，可能是因为它们主要以双自由基结构存在的缘故。解离反应的内能相关：联苯及其取代物的双电荷离子[C_(12)H_(10)]~(2+)等的单分子解离同不稳定离子在离子源中的解离有较大的差别，主要是由离子的内能不同引起的，而[C_(12)H_(10)]~(2+)的CID谱则趋向于2E谱的特征。取代基效应：吸电性取代基的存在会使双电荷离子主要以丢失取代基的方式解离（如卤代甲苯双电荷离子的解离），对一个有规律的体系，如取代联苯类双电荷离子取代基对反应的影响可基本用Hammett方程来描述。邻位效应：苯二胺双电荷离子的CID中性丢失有明显的邻位效应。而卤代甲苯化合物的ECID谱出现邻位效应，这表明同亚稳双电荷离子不同，稳定的双电荷离子仍保持中性分子的结构特征。靶气效应：在一定的压力范围内，靶气的压力一般不影响ECID谱（对苯甲酰胺双电荷离子）及2E谱（对联苯双电荷离子）的谱图特征。靶气的电离势影响离子的内能，但不影响ECID谱的特征（对[C_2H_4]~(2+)）。

微生物对抗菌肽耐受的诱导及耐受机理初步研究

抗菌肽是一类具有强大杀菌能力的肽类分子，同时还具有离子调节、免疫调节、蛋白酶抑制剂和自由基清除等其他生物活性。现已鉴定的抗菌肽超过1,200 种，几乎存在于所有生物种类中。在抗生素耐受严重的今天，抗菌肽极有潜力成为新型的有效抗菌药物，许多抗菌肽已进入临床前研究或临床研究。在本论文中，我们选择了无指盘臭蛙（Odorrana grahami）来源的三种抗菌肽（Brevinin 2E-OG1、Nigrocin-OG4 和Palustrin-OG1），单独或组合使用，以藤黄微球菌（Micrococcus luteus）、枯草芽孢杆菌（Bacillus subtilis）和白假丝酵母菌（Candida albicans）为研究对象，进行微生物对抗菌肽耐受性的实验诱导；并通过检测胞外蛋白酶活性、蛋白质组学等方法对微生物耐受抗菌肽机制进行初步的研究。将微生物培养于含有低浓度抗菌肽（单独使用或组合使用）培养基中，每日转接一次，每十次酌情提高抗菌肽浓度。80 次转接后，除藤黄微球菌未对 Palustrin-OG1 产生耐受外，其余所有的实验菌株均表现出对所用三种抗菌肽的耐受。但是Palustrin-OG1 与Brevinin 2E-OG1 或Nigrocin-OG4 联合使用能在一定程度上降低耐受性。将诱导后细菌于不含抗菌肽条件下培养，转接5 次后，对耐受现象无影响，说明这种耐受是可以稳定遗传的。抗菌肽耐受机制之一是分泌蛋白酶水解胞外抗菌肽，我们通过两种方式检测胞外蛋白酶活性，一种是检测发酵液的酪蛋白水解活性，另一种是检测发酵液处理抗菌肽后对抗菌活性的影响。结果发现枯草芽孢杆菌和藤黄微球菌发酵液存在着蛋白酶活性，推测胞外蛋白酶可能与二者对抗菌肽的耐受有关；而白假丝酵母菌发酵液中未检测到蛋白酶活性。另外，我们还通过蛋白质组学的手段对枯草芽孢杆菌耐受机制进行了初步的研究，鉴定了5 个差异表达的蛋白，表达上调的蛋白有yraA（功能未知）、Tpx （巯基过氧化物酶，Thiol peroxidase）、pdhD（二氢硫辛酰胺脱氢酶，dihydrolipoamide dehydrogenase），表达下调的有cotN/TasA（芽孢膜相关蛋白，spore coat-associated protein）和gapA（三磷酸甘油醛脱氢酶，Glyceraldehyde 3-phosphate dehydrogenase 1 ，GAPDH）。yraA 和Tpx 都由Spx 调控，yraA 可以水解小肽增加自由氨基酸，而自由氨基酸增多时gapA、tasA 表达水平会下降，Spx 是由sigma-M 因子调控的，所以我们推测sigma-M 因子在B. subtiis 对抗菌肽耐受中起到了重要的作用。总之，本研究发现抗菌肽的联合作用会减缓微生物对其耐受的程度，为抗菌肽类药物研发提供了一种新思路；同时对抗菌肽耐受机制的初步研究也为今后的深入研究打下了基础。另外，我们还设计了一种新型的抗菌肽系统命名方法，并构建了昆明动物研究所抗菌肽数据库。

唐古特瑞香和大果大戟的化学成分研究

本学位论文由两部分共3章组成。第一部分分别报道2种藏药唐古特瑞香和大果大戟化学成分的研究成果，从2种药用植物共分离鉴定了60个不同的化合物，其中12个为新结构，特别有意义的是发现了2个具有同一新骨架的二萜化合物。第二部分概述了大戟科植物多环二萜的研究进展。 第一部分包括第1和2章。在这2章中分别报道了唐古特瑞香（Daphne tangutica Maxim）和大果大戟（Euphorbia wallichii Hook. f. Fl）化学成分的分离纯化与结构鉴定。实验采用正、反相硅胶柱层析、薄层制备及HPLC等分离方法，从唐古特瑞香的根皮中共分离出32个化合物，通过红外、质谱及核磁共振等波谱方法鉴定了其中的31个，结构类型分别属于瑞香二萜类、木脂素类、香豆素类、苯丙素类及甾体类，其中有三个新的瑞香二萜型化合物，经波谱分析将它们的结构分别鉴定为1,2a-二氢-20-棕榈酰瑞香毒素、1,2a-二氢-5b-羟基-6a,7a-环氧-树脂大戟醇-14-苯甲酸酯及1,2b-二氢-5b-羟基-6a,7a-环氧-树脂大戟醇-14-苯甲酸酯，另外还有13个已知化合物为首次从该植物中分离得到。从大果大戟的根部共分离出33个化合物，鉴定了其中的30个，其主要成分为种类丰富的二萜，包括巨大戟烷型、续随子烷型、对映－阿替生烷型、对映－贝壳杉烷型、对映－松香烷型、ent-trachylobane型、对映－异海松烷型及一新骨架五环二萜ent-wallichane型，另外还有香豆素、甾体、三萜和一些简单的小分子化合物。其中新化合物有9个，经波谱分析将它们的结构分别鉴定为5-O-(2E,4E,6E)-癸三烯酰基-3,20-O-二乙酰基巨大戟醇、5-O-(2E,4Z)-癸二烯酰基-3-O-乙酰基-20-去氧巨大戟醇、3-O-(2E,4Z)-癸二烯酰基-5b,6b-氧-交京大戟醇、7-苯甲酰氧基-3,5,15-三乙酰基-续随子醇、ent-trachylobane-3-one-17-oic-acid、3α-羟基-对映-阿替斯-16-烯-14-酮、3α,6-二羟基-对映-异海松-7-烯-2,15-二酮、wallichanol A 和 wallichanol B，其中，wallichanol A 和 wallichanol B属于一新骨架类型的五环二萜。除此以外，另有13个已知化合物为首次从该植物中分离得到。 第2部分即第3章，首次概述了大戟属植物中多环二萜的化学和药理研究进展。 This dissertation is composed by two parts. The first part reports the phytochemical investigation of two Tibetan medicine plants, Daphne tangutica Maxim and Euphorbia wallichii Hook. f. Fl. Sixty different compounds including ten new compounds and two novel diterpenoids possessing a new carbon skeleton were isolated and identified. The second part is a review about the progress of studies on the polycyclic diterpeniods of the plant family of Euphorbia. The first part consists two chapters, which expatiate on the isolation and identification of chemical constituents from D. tangutica and E. wallichii. Thirty-one compounds were isolated from the root barks of D. tangutica by methods of column chromatography (silica gel, including reversed phase), preparative TLC and HPLC, and their structure were identified as nine daphnane diterpenes, six lignans, nine cumarin derivatives, five phenylpropanoid derivatives, a steroids and a benzoate on the basis of spectroscopic methods including IR, MS and NMR. Among them, three are new diterpenes with skeleton of daphnane and the structure were determined as 1,a-dihydro-20-palimoyl-daphnetoxin, 1,2a-dihydro-5b- hydroxy-6a,7a-epoxy-resiniferonol-14-benzoate and 1,2b-dihydro-5b-hydroxy- 6a,7a-epoxy-resiniferonol-14-benzoate. In addition, thirteen known ones were isolated from this plant for the first time. Isolation of the roots of E. wallichii yielded thirty compounds, twenty-four of them were elucidated as diterpenoids, which belong to different skeleton types of ingenol, lathyrane, ent-atisane, ent-kaurane, ent-abietane, ent-trachylobane, ent-isopimarane and a new pentacyclic skeleton ent-wallichane respectively. The remains including a cumarine, a triterpenoid, a steroid and three compounds with small molecule. Nine new compounds were characterized as 5-O-deca-2E,4E,6E- trienoyl-3,20-O-diacetylingenol, 5-O-deca-2E,4Z-dienoyl-3-O-acetyl-20- deoxyingenol, 3-O-deca-2E,4Z-dienoyl-jolkinol-5b,6b-oxide, 7-benzoyl-3,5,15- triacetyl-7-hydroxylathyrol, ent-trachylobane-3-one-17-oic-acid, 3α-hydroxy-ent- atis-16-en-14-one, 3α,6-dihydroxy-ent-isopimarane-7-en-2,15-dione, wallichanol A and wallichanol B, respectively, by means of comprehensive spectroscopic analysis. Among them, wallichanol A and wallichanol B were two notable novel pentacyclic diterpenoids processing a new rearranged carbon skeleton. And more, thirteen ones were firstly reported from this plant. The third chapter summarizes the research development on chemistry and pharmacology of polycyclic diterpenes from the plant family of Euphorbia for the first time.

Multi-electron processes in 4.15-11.08 keV/u(13)C(6+) on argon collisions

The relative partial cross sections for C-13(6+)-Ar collisions at 4.15-11.08 keV/u incident energy are measured. The cross-section ratios sigma(2E)/sigma(SC), sigma(3E)/sigma(SC), sigma(4E)/sigma(SC) and sigma(5E)/sigma(SC) are approximately the constants of 0.51 +/- 0.05, 0.20 +/- 0.03, 0.06 +/- 0.03 and 0.02 +/- 0.01 in this region. The significance of the multi-electron process in highly charged ions (HCIs) with argon collisions is demonstrated (sigma(ME)/sigma(SC) as high as 0.79 +/- 0.06). In multi-electron processes, it is shown that transfer ionization is dominant while pure electron capture is weak and negligible. For all reaction channels, the cross-sections are independent of the incident energy in the present energy region, which is in agreement with the static characteristic of classic models, i.e. the molecular Coulomb over-the-barrier model (MCBM), the extended classical over-the-barrier (ECBM) and the semiempirical scaling laws (SL). The result is compared with these classical models and with our previous work of C-13(6+)-Ne collisions

Evidence of strong projectile-target-core interaction in single ionization of neon by electron impact

The momentum distributions of recoil ions were measured in the single ionization of neon by electron impact at incident energies between 80 and 2300 eV. It was found that there are a noticeable number of recoil ions carrying large momenta, and the relative contributions of these ions becomes more pronounced with the further decrease of incident electron energy. These observed behaviors indicate that there is a strong projectile-target-core interaction in the single-ionization reaction. By comparing our results with those of electron-neon elastic scattering, we concluded that the elastic scattering of the projectile electron on the target core plays an important role at low and intermediate collision energies.

Synthesis, structural characterization, and ethylene polymerization behavior of the vanadium(III) complexes bearing salicylaldiminato ligands

Vanadium(III) complexes bearing salicylaldiminato ligands (2a-k) [RN=CH(Ar0)]VCl2(THF)2 (Ar C61714, R = Ph, 2a; p-CF3Ph, 2b; p-CH3Ph, 2c; 2,6-Me2Ph, 2d; 2,6-iPr2Ph, 2e; cyclohexyl, 2f; Ar = C6H3tBu(2), R = Ph, 2g; 2,6-iPr2Ph, 2h; Ar = C6H2tBU2(2,4), R = Ph, 2i; 2,6-iPr2Ph, 2j; Ar = C6H2Br2, R = Ph, 2k) were prepared from VC13(THF)3 by treating with 1.0 equiv of (RN=CH)ArOH in tetrahydrofuran (THF) in the presence of excess triethylamine (TEA).

Synthesis, Structural Characterization, and Olefin Polymerization Behavior of Vanadium(III) Complexes Bearing Tridentate Schiff Base Ligands

Vanadium(III) complexes bearing tridentate salicylaldiminato ligands (2a-f) [OC6H4CH=NL]VCl2(THF) (L = CH2CH2OMe, 2a; CH2CH2NMe2, 2b; CH2C5H4N, 2c; 8-C9H6N (quinoline), 2d; 2-MeSC6H4, 2e; 2-Ph2PC6H4, 2f) and tridentate beta-enaminoketonato ligands [OC6H8CH=N-2-Ph2PC6H4]VCl2(THF) (2g) and [O(Ph)C=CHCH=N-2-Ph2PC6H4]VCl2(THF) (2h) were prepared from VCl3(THF)(3) by treating with 1.0 equiv of the deprotonated ligands in tetrahydrofuran (THF). These complexes were characterized by FTIR and mass spectrometry as well as elemental analysis. Structures of complexes 2e, 2f, and 2h were further confirmed by X-ray crystallographic analysis. These complexes were investigated as catalysts for olefin polymerization in the presence of organoaluminum compounds. On activation with Et2AlCl, complexes 2a-h exhibited high catalytic activities toward ethylene polymerization (up to 20.64 kg PE/mmol(v) center dot h center dot bar) even at high temperature, suggesting these catalysts possess high thermal stability.

Novel vanadium(III) complexes with bidentate N,N-chelating iminopyrrolide ligands: synthesis, characterization and catalytic behaviour of ethylene polymerization and copolymerization with 10-undecen-1-ol

A series of novel vanadium(III) complexes bearing iminopyrrolide chelating ligands [2-(RN=CH)C4H3N]V(THF)(2)Cl-2 (2a: R = cyclohexyl; 2b: R = Ph; 2c: R = 2,6-iPr(2)C(6)H(3); 2d: R = p-CF3C6H4; 2e: R = C6F5) have been synthesized and characterized. Single-crystal X-ray diffraction revealed that complexes 2a, 2c and 2e adopt an octahedral geometry around the vanadium center. In the presence of Et2AlCl as a co-catalyst, these complexes displayed high catalytic activities up to 48.6 kg PE mmol(V)(-1) h(-1) bar(-1) for ethylene polymerization, and produced high molecular weight polymers. 2a-e/Et2AlCl catalytic systems were tolerant to elevated temperature (70 degrees C) and yielded unimodal polyethylenes, indicating the single site behaviour of these catalysts. By pre-treating with equimolar amounts of alkylaluminums, functional alpha-olefin 10-undecen-1-ol can be efficiently incorporated into polyethylene chains. 10-Undecen-1-ol incorporation can easily reach 15.8 mol% under the mild conditions.

联吡啶还原合成吡啶基四氢吡啶和吡啶基六氢吡啶

吡啶基四氢吡啶衍生物(Ⅰ)和吡啶基六氢吡啶衍生物(Ⅱ)是α受体和HT1A受体类似物的结构组成部分,应用在药物合成中[1].Ⅰ和Ⅱ可通过环化反应、烷基化反应或联吡啶还原合成[2].环化反应或烷基化反应路线较长,且易形成含不饱和哌啶基吡啶的混合物,需要进一步的还原或纯化[2a];用Ni合金还原联吡啶只能直接合成吡啶基六氢吡啶,且反应时间长,收率低[2d];N-氧化联吡啶还原合成吡啶基六氢吡啶收率低,不适用于大量合成[2e].

氯化物熔盐中Nd~(3+)在液体Ga电极上还原的电化学行为

本文利用循环V-A法(CV)研究了Nd~(3+)在液体Ga电极上还原的电化学反应动力学。结果表明,Nd~(3+)在Ga电极上的还原是分步进行的。第一步在较高的电位扫描速度下为扩散控制的可逆电荷传递反应,即Nd~(3+)+e?Nd~(2+);在电位扫描速度较低时,随后的化学反应为第一步反应的控制步骤,即Nd~(3+)+e?快Nd~(2+)+mCl→慢NdCl_m~(2-m)。第二步为不可逆的电荷传递反应,即沉积的金属Nd与Ga合金化,Nd~(2+)+2e→Nd(Ga)。估算了该反应的标准反应速度常数为7.0×10~(-3)cm/s。

A new acylated iridoid glucoside from Avicennia marina

A new acylated iridoid glucoside, namely, 2'-O-(5-phenyl-2E, 4E-pentadienoyl)mussaenosidic acid, was isolated from the aerial parts of the mangrove plant Avicennia marina. The structure of the new compound was established on the basis of various NMR spectroscopic analyses, including 2D NMR techniques (H-1-H-1 COSY, HMQC, and HMBC) and HR-FAB-MS. This compound displayed moderate antioxidant activity.

红树林植物海榄雌化学成分研究

本论文对红树林植物海榄雌的化学成分进行了研究，对其中分离得到的部分化合物进行了初步的生物活性筛选。 海榄雌采自海南东寨港，样品干燥后用氯仿甲醇（1：1）浸泡提取，合并提取物，先后用石油醚、乙酸乙酯和正丁醇萃取。得到石油醚相、乙酸乙酯相、正丁醇相和水相。 各部分采用常规的硅胶柱层析、制备薄层层析、凝胶Sephadex LH-20柱层析、反相硅胶柱层析、半制备HPLC以及重结晶等手段分离得到28个化合物。利用各种现代波谱技术(IR、UV、ESI-MS、FAB-MS、HR-FAB-MS、1D-NMR、2D-NMR等)，确定了其中20个化合物的结构，其中包括2个新化合物：化合物A1 2′-O-(5-phenyl-2E, 4E-pentadienoyl)mussaenosidic acid和化合物A2 2′-O-(p-methoxycinnamoyl)mussaenosidic acid，以及13个首次从海榄雌中报道的化合物。 对得到的20个化合物A1－A20进行了DPPH自由基清除活性筛选，化合物A4、A5、A6和A16表现出较好的活性，其IC50分别为9.61 μg/mL、8.55 μg/mL、11.72 μg/mL和7.73 μg/mL；化合物A13和A15表现出中等强度的DPPH自由基清除活性，其IC50分别为34.80 μg/mL和44.90 μg/mL；其他化合物只表现出微弱活性，其IC50均大于100 μg/mL；阳性对照BHT的IC50为18.00 μg/mL。 对分离得到的部分样品进行了抑菌活性测试，各样品在测试浓度下对测试菌均未表现出明显的抑菌活性。

The electrochemical reduction reaction of dissolved oxygen on Q235 carbon steel in alkaline solution containing chloride ions

Cyclic voltammetry, electrochemical impedance spectroscopy, and rotating disk electrode voltammetry have been used to study the effect of chloride ions on the dissolved oxygen reduction reaction (ORR) on Q235 carbon steel electrode in a 0.02 M calcium hydroxide (Ca(OH)(2)) solutions imitating the liquid phase in concrete pores. The results indicate that the cathodic process on Q235 carbon steel electrode in oxygen-saturated 0.02 M Ca(OH)(2) with different concentrations of chloride ions contain three reactions except hydrogen evolution: dissolved oxygen reduction, the reduction of Fe(III) to Fe(II), and then the reduction of Fe(II) to Fe. The peak potential of ORR shifts to the positive direction as the chloride ion concentration increases. The oxygen molecule adsorption can be inhibited by the chloride ion adsorption, and the rate of ORR decreases as the concentration of chloride ions increases. The mechanism of ORR is changed from 2e(-) and 4e(-) reactions, occurring simultaneously, to quietly 4e(-) reaction with the increasing chloride ion concentration.