(三唑基-~(14)C-)粉锈宁的标记合成

本文报道了(三唑基-14C)-粉锈宁的制备。由14C-甲酸和重碳酸氨基胍形成(5-14C)-3-氨基-1,2,4-三唑,再经重氮化脱氨得到(5-14C)-1,2,4-三唑,最后再与对氯酚和二氯片呐酮反应得到(三唑基-14C)-粉锈宁。放化收率为26％(从甲酸-14C计),放化纯度大于95％。     

~(14)C-马拉硫磷及其混剂对玉米螟幼虫体表的穿透能力

(14)~C-马拉硫磷单剂,(14)_C-马拉硫磷与敌百虫,(14)~C-马拉硫磷与NIA_(10388)、(14)~C-马拉硫磷与敌百虫和NIA_(16388)混剂分别点滴玉米螟幼虫。5小时后每头幼虫体内的放射性活度分别为277、653、645和701dpm。不同混剂点滴,幼虫体内的放射性活度分别是马拉硫磷单剂的2.36,2.33和2.53倍。可见马拉硫磷混剂对玉米螟幼虫体表有较强的穿透能力。     

~(35)S-多噻烷的制备

(35)~S-多噻烷,即(35)~S-7-二甲氨基-1,2,3,4,5-五硫环辛烷,是由Na_2~(35)SO_4制备Na_2~(35)S,进而制备Na_2~(35)SS_x,再与氯化物缩合而成,放化收率33.6％,放化纯度97％。     

除草剂虎威的标记合成

5-( 2-氯-4-三氧甲基 )苯氧基 )- N-(甲基磺酰基 ) - 2-硝基苯甲酰胺 (虎威 )的14 C标记合成经 6步完成。其放化收率为 1 8 1 5 % (以14 C 以苯甲酸计 ) ,放化纯度经薄板检测大于 99%。     

高比活度碳-14标记氟噻草胺的合成与分析

为开展除草剂氟噻草胺在我国的登记代谢试验,本研究以4-氟[U-¹⁴C]苯胺为同位素原料,经还原胺化、缩合、取代、水解和醚化五步放化反应获得N-(4-氟[U-¹⁴C]苯基)-N-异丙基-2-((5-(三氟甲基)-1,3,4-噻二唑-2-基)氧基)乙酰胺(2,总活度201.65 MBq;比活度2 049.80 MBq·mmol^-1;化学纯度和放化纯度均大于98%,总放化收率39%);以[¹⁴C]硫氰酸钠为同位素原料,经加成、水解、环化、重氮化和醚化五步放化反应获得N-(4-氟苯基)-N-异丙基-2-((5-(三氟甲基)-1,3,4-[2-¹⁴C]噻二唑-2-基)氧基)乙酰胺(3,总活度287.86 MBq;比活度2 042.40 MBq·mmol^-1;化学纯度和放化纯度均大于98%,总放化收率14%)。两种标记物的结构经核磁共振氢谱(¹H NMR)和质谱(MS)分析确认,质量指标经高效液相色谱(HPLC-PDA)、放射性薄层成像分析(TLC-IIA)、在线放射性高效液相色谱(HPLC-FSA)和液体闪烁法(LSC)测定,均可作为放射性示踪剂。本研究结果为氟噻草胺的同位素示踪研究(包括该除草剂在我国的登记代谢试验)奠定了物质基础。     

水稻对~(134)Cs的吸收和~(134)Cs在水稻-土壤中的分配

试验表明,水稻对~(134)Cs的吸收,孕穗期吸收速率最快;土壤理化性质不同,吸附~(134)Cs的能力有差异;不同生育期灌溉~(134)Cs溶液,水稻对其吸收量不同,离成熟期近,吸收得多;灌溉次数多和灌溉水中~(134)Cs活度高,水稻吸收的~(134)Cs也多。糙米经精白加工后,可使~(134)Cs的污染减少22.6—45.6％;~(134)CS在水稻各部位比活度大小的顺序为糠>根>稻草>谷壳>精白米;活度以稻草中最高,占水稻植株总活度的51.4％,糙米、根和谷壳分别占28.4％。11.8％和8.4％:~(134)Cs在土壤中移动很少,有95.1％集中在0—2.5cm的表土层内;~(134)Cs在水稻-土壤中的分配为6.1％:93.9％;K~+抑制水稻对~(134)Cs的吸收,K~+浓度与水稻中~(134)Cs比活度之间呈指数回归形式。     

应用~(15)N~(32)P示踪技术研究水稻对不同复(混)合肥料中氮磷的吸收

在盆栽条件下几种复(混)合肥料对水稻均有增产作用,与对照相比稻谷增产60.8—77.7％,达到显著水准。但几种复(混)合肥之间无显著差异。用15～(N)示踪法测定水稻对复(混)合肥的氮素利用率:尿素磷铵为44.7％,氯磷铵为44.5％,尿素为44.1％,尿素加普通过磷酸钙(简称普钙)为40.8％,硝酸磷肥为36.4％。说明硝酸磷肥不宜于水稻田施用。用~(32)P示踪法测定水稻对几种复(混)合肥的磷的利用率:硝酸磷肥为22.6％,氯磷铵为22.4％,尿素磷铵为21.1％,尿素加普钙为20.7％,普钙为11.9％。水稻对供试复(混)合肥料磷的利用率均显著高于普钙。     

氨甲喋呤(MTX)的直接碘标记方法研究

本文报道了~125I(~131I)抗肿瘤药物氨甲喋呤的制备方法,用直接碘化法——NBS、ChT、Iodogen进行标记,并对这几种方法进行了比较。结果表明,NBS法最好,标记率达90—99％。经Sephadex G-75柱凝胶过滤后得到纯产品,放化纯度为95.4％。所制得的标记产品适用于示踪研究。     

水稻对~(14)CO_3~(2-)的吸收和积累动态

用同位素示踪技术研究水稻对14CO32-的吸收和积累动态,及其在水稻田中的行为特性。结果表明:通过水稻根系和浸于水中的茎杆下部吸收的14CO32-离子会向上部组织输送并形成积累趋势;在上部组织中,叶和茎杆上部的14C比活度随时间呈逐渐上升的趋势,而穗中的比活度于14d达最大值(271.9Bq/g)后又呈下降趋势;茎杆下部由于直接浸于水中,表现出对14CO32-离子的快速吸收、吸附,此后随时间呈下降趋势,根部表现出上升过程迟后于茎杆下部,其14C比活度也低于茎杆下部。上部组织(穗、叶和茎杆上部)中14C的百分含量随时间上升,而下部组织(茎杆下部和根)则相反,至试验后期(21~35d),其百分含量基本持平(约各占50%),14C从下部组织向上部组织输送的特征非常明显。     

由质粒介导的豌豆根瘤菌(Rhizobium Leguminosarum)Nif D::Tn5向棕色固氮菌(Azotobacter vinelandii)的转移

通过助移质粒P~(PK2013)的推动,实现了携带豌豆根瘤菌(Rhizobium Legumi-nosarum)nif D::Tn5的质粒pRK2009由大肠杆菌(E.coli)向棕色固氮菌Az-otobacter vinelandii的转移,转移频率为每受体7×10~(-5),进一步将与pRK2509不相容的质粒pPHLJI转入这个转移接合子,筛选得到了两株相同的棕色固氮菌的突变菌株。由表型特征分析和活性互补实验证明该突变菌株在染色体中含有豌豆根瘤茵nif D::Tn5,是两不同种固氮微生物的固氮基因即豌豆根瘤菌nif D与棕色固氮菌nif D之间发生同源性重组的结果     

Antioxidant and cyclooxygenase activities of fatty acids found in food

Several commercially available C-8 to C-24 saturated and unsaturated fatty acids (1-29) were assayed for cyclooxygenase-I (COX-I) and cyclooxygenase-II (COX-II) inhibitory and antioxidant activities. Among the saturated fatty acids tested at 60 microg mL(-1), there was an increase in antioxidant activity with increasing chain length from octanoic acid to myristic acid (C-8-C-14) and a decrease thereafter. All unsaturated fatty acids tested at 60 microg mL(-1) showed good antioxidant activity except for undecylenic acid (12), cis-5-dodecenoic acid (13), and nervonic acid (29). The highest inhibitory activities among the saturated fatty acids tested on cyclooxygenase enzymes COX-I and COX-II were observed for decanoic acid to lauric acid (3-5) at 100 microg mL(-1). Similarly, among the unsaturated fatty acids tested, the highest activities were observed for cis-8,11,14-eicosatrienoic acid (25) and cis-13,16-docosadienoic acid (27) at 100 microg mL(-1).     

Carbohydrate and amino acid degradation pathways in L-methionine/D-[13C] glucose model systems

Maillard model systems consisting of labeled D-[(13)C]glucoses, L-[(15)N]methionine, and L-[methyl-(13)C]methionine, have been utilized to identify the amino acid and carbohydrate fragmentation pathways occurring in the model system through Py-GC/MS analysis. The label incorporation analyses have indicated that the carbohydrate moiety produces 1-deoxy- and 3-deoxyglucosones and undergoes C(2)/C(4) and C(3)/C(3) cleavages to produce glycolaldehyde, tetrose, and C(3)-reactive sugar derivatives such as acetol, glyceraldehyde, and pyruvaldehyde. Glycolaldehyde was found to incorporate C-1, C-2 (70%) and C-5, C-6 (30%) glucose carbon fragments, whereas the tetrose moiety incorporates only C-3, C-4, C-5, C-6 glucose carbon atoms. In addition, the major source of reactive C(3) fragments was found to contain C-4, C-5, C-6 sugar moiety. On the other hand, methionine alone also generated Strecker aldehyde as detected by its condensation product with 3-(methylthio)propylamine. Plausible mechanisms were proposed for the formation of the interaction products between sugar and amino acid degradation products on the basis of the label incorporation patterns.     

Simultaneous derivatization and trapping of volatile products from aqueous photolysis of thiamethoxam insecticide

An aqueous photolysis study was conducted with radiolabeled thiamethoxam, 4H-1,3,5-oxadiazin-2-imine, 3-[(2-chloro-5-thiazolyl)methyl]tetrahydro-5-methyl-N-nitro, to establish the relevance of aqueous photolysis as a transformation process for (14)C-[thiazolyl]-thiamethoxam. (14)C-[thiazolyl]-thiamethoxam was applied to sterile sodium acetate pH 5 buffer solution at a dose rate of approximately 10 ppm. The resulting samples were incubated for up to 30 days at 25 degrees C under irradiated and nonirradiated conditions. The irradiated samples were exposed to a 12-hour-on and 12-hour-off light cycle. Volatile fractions accounted for up to an average of 56.76% of the total dose for the irradiated incubations and <0.08% for the nonirradiated incubations. These fractions were proposed to be a mixture of carbonyl sulfide (COS) and isocyanic acid (CONH). Verification of these components was accomplished by trapping with cyclohexylamine and formation of the thiocarbamate and the isocyanic acid derivatives. A similar method of trapping thiocarbamate metabolites was reported (Chen and Casida, 1978) where filter paper saturated with isobutylamine in methanol was arranged to trap (14)COS and (14)CO(2) under a positive flow of O(2) at 25 degrees C. Mass spectroscopy of the derivatized components confirmed the presence of carbonyl sulfide as the cyclohexylamine thiocarbamate and of isocyanic acid as its cyclohexylamine derivative. Evidence from this study indicates that thiamethoxam degrades significantly under photolytic conditions.     

Novel antiallergic catechin derivatives isolated from oolong tea.

Two catechin derivatives (C-1 and C-2) with potent antiallergic activity were isolated from Taiwanese oolong tea by HPLC techniques. From NMR and FAB-MS analyses, the structures of C-1 and C-2 were elucidated as (-)-epigallocatechin 3-O-(3-O-methyl)gallate and (-)-epigallocatechin 3-O-(4-O-methyl)gallate, respectively. The oolong tea leaves contained 0.34% (dry weight) C-1 and 0.20% C-2. Traces of C-2 were detected in only 1 of 15 varieties of green tea tested. C-1 was detected in 13 of 15 green tea varieties; C-1 was most concentrated in tea cultivars classified as Assam hybrids (0. 50-0.82% of dry weight). Quantitative analyses of green tea, oolong tea, and black tea manufactured from same batches of tea leaves showed that neither catechin derivative was produced during the fermentation process. Oral doses of C-1 and C-2 (5-50 mg/kg) significantly inhibited type I allergic (anaphylactic) reactions in mice sensitized with ovalbumin and Freund's incomplete adjuvant. These inhibitory effects exceeded that of the major tea catechin, (-)-epigallocatechin 3-O-gallate, which has known antiallergic properties.     

Antifeedant and mosquitocidal compounds from Delphinium x cultorum cv. Magic fountains flowers

Six volatile compounds, ethylmethylbenzene (1), 1-isopentyl-2,4, 5-trimethylbenzene (2), 2-(hex-3-ene-2-one)phenylmethyl ketone (3), E and Z isomers of 3-butylidene-3H-isobenzofuran-1-one (4 and 5), and 2-penten-1-ylbenzoic acid (6), were isolated from the mosquitocidal hexane extract of Delphinium x cultorum cv. Magic Fountains flowers. In addition, the ethyl acetate extract, which displayed corn earworm antifeedant activity, yielded 4-hydroxybenzoic acid (7) and bis(4-hydroxyphenyl)methanol (8). However, compounds 7 and 8 were not biologically active.     

Sugar fragmentation in the maillard reaction cascade: isotope labeling studies on the formation of acetic acid by a hydrolytic beta-dicarbonyl cleavage mechanism

The formation of acetic acid was elucidated based on volatile reaction products and related nonvolatile key intermediates. The origin and yield of acetic acid were determined under well-controlled conditions (90-120 degrees C, pH 6-8). Experiments with various 13C-labeled glucose isotopomers in the presence of glycine revealed all six carbon atoms being incorporated into acetic acid: C-1/C-2 ( approximately 70%), C-3/C-4 ( approximately 10%), and C-5/C-6 (approximately 20%). Acetic acid is a good marker of the 2,3-enolization pathway since it is almost exclusively formed from 1-deoxy-2,3-diulose intermediates. Depending on the pH, the acetic acid conversion yield reached 85 mol % when using 1-deoxy-2,3-hexodiulose (1) as a precursor. Hydrolytic beta-dicarbonyl cleavage of 1-deoxy-2,4-hexodiuloses was shown to be the major pathway leading to acetic acid from glucose without the intermediacy of any oxidizing agents. The presence of key intermediates was corroborated for the first time, i.e., tetroses and 2-hydroxy-3-oxobutanal, a tautomer of 1-hydroxy-2,3-butanedione, also referred to as 1-deoxy-2,3-tetrodiulose. The hydrolytic beta-dicarbonyl cleavage represents a general pathway to organic acids, which corresponds to an acyloin cleavage or a retro-Claisen type reaction. Although alternative mechanisms must exist, the frequently reported hydrolytic alpha-dicarbonyl cleavage of 1 can be ruled out as a pathway forming carboxylic acids.     

Flavone C-glycosides from leaves of Oxalis triangularis

The flavone C-glycosides luteolin 6-C-(2'-O-beta-xylopyranosyl-beta-glucopyranoside) (1), apigenin 6-C-(2'-O-alpha-rhamnopyranosyl-beta-glucopyranoside) (2), apigenin 6-C-(2'-O-beta-xylopyranosyl-beta-glucopyranoside) (3), apigenin 6-C-(2'-O-(6'-(E)-caffeoylglucoside)-beta-glucopyranoside) (4), and apigenin 6-C-(2'-O-(6'-(E)-p-coumaroylglucoside)-beta-glucopyranoside) (5) have been isolated from the purple leaves of Oxalis triangularis. Compound 4 is new, while 5 has previously been isolated from Cucumis sativus after treatment with silicon and infection with Sphaerotheca fuliginea. Signal duplication in the NMR spectra of 2, 4, and 5 revealed the presence of rotameric conformers, created by rotational hindrance at the C(sp3) -C(sp2) glucosyl-flavone linkage in these flavone C-glycosides.     

Synergistic effects of thiols and amines on antiradical efficiency of protocatechuic acid

DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity of protocatechuic acid and its structural analogues (methyl protocatechuate, 3',4'-dihydroxyacetophenone, 3,4-dihydroxybenzaldehyde, and 3,4-dihydroxybenzonitrile) were examined in aprotic and protic solvents. In aprotic acetonitrile, all test compounds scavenged two radicals. In protic methanol, however, these compounds rapidly scavenged five radicals except for protocatechuic acid, which consumed only two radicals. The result indicated that higher radical scavenging activity in methanol than in acetonitrile was due to a nucleophilic addition of the methanol molecule on the oxidized quinones, which led to a regeneration of catechol structures. To investigate the importance of the nucleophilic addition on the quinones for the high radical scavenging activity, DPPH radical scavenging activity of protocatechuic acid and its analogues was examined in the presence of a variety of nucleophiles. The addition of a strong nucleophile such as a cysteine derivative significantly increased the radical scavenging equivalence. Furthermore, thiol adducts at C-2 and C-2,5 of protocatechuic acid and its analogues were isolated from the reaction mixtures. These results strongly suggest that the quinone of protocatechuic acid and its analogues undergo a nucleophilic attack at C-2 to yield 2-substituted-3,4-diols. Then, a regenerated catechol moiety of adducts scavenge two additional radicals by reoxidation into quinones, which undergo the second nucleophilic attack at the C-5. This mechanism demonstrates a possibility of synergistic effects of various nucleophiles on the radical scavenging ability of plant polyphenols containing a 3,4-dihydroxy substructure like protocatechuic acid and its analogues.     

Isolation and structure elucidation of highly antioxidative 3,8″-linked biflavanones and flavanone-C-glycosides from Garcinia buchananii bark

The aim of this study was to identify antioxidants from Garcinia buchananii bark extract using hydrogen peroxide scavenging and oxygen radical absorbance capacity (ORAC) assays. LC-MS/MS analysis, 1D- and 2D-NMR, and circular dichroism (CD) spectroscopy led to the unequivocal identification of the major antioxidative molecules as a series of three 3,8″-linked biflavanones and two flavanone-C-glycosides. Besides the previously reported (2R,3R,2″R,3″R)-naringenin-C-3/C-8″ dihydroquercetin linked biflavanone (GB-2; 4) and (2R,3S,2″R,3″R)-manniflavanone (3), whose stereochemistry has been revised, the antioxidants identified for the first time in Garcinia buchananii were (2R,3R)-taxifolin-6-C-β-D-glucopyranoside (1), (2R,3R)-aromadendrin-6-C-β-D-glucopyranoside (2), and the new compound (2R,3S,2″S)-buchananiflavanone (5). The H?O? scavenging and the ORAC assays demonstrated that these natural products have an extraordinarily high antioxidative power, especially (2R,3S,2″R,3″R)-manniflavanone (3) and GB-2 (4), with EC?? values of 2.8 and 2.2 μM, respectively, and 13.73 and 12.10 μmol TE/ μmol. These findings demonstrate that G. buchananii bark extract is a rich natural source of antioxidants.