Differences in the rDNA-bearing chromosome divide the Asian-Pacific and Atlantic species of Crassostrea (Bivalvia, Mollusca)

Karyotype and chromosomal location of the major ribosomal RNA genes (rDNA) were studied using fluorescence in situ hybridization (FISH) in five species of Crassostrea: three Asian-Pacific species (C. gigas, C. plicatula, and C. ariakensis) and two Atlantic species (C. virginica and C. rhizophorae). FISH probes were made by PCR amplification of the intergenic transcribed spacer between the 18S and 5.8S rRNA genes, and labeled with digoxigenin-11-dUTP. All five species had a haploid number of 10 chromosomes. The Atlantic species had 1-2 submetacentric chromosomes, while the three Pacific species had none. FISH with metaphase chromosomes detected a single telomeric locus for rDNA in all five species without any variation. In all three Pacific species, rDNA was located on the long arm of Chromosome 10 (10q)-the smallest chromosome. In the two Atlantic species, rDNA was located on the short arm of Chromosome 2 (2p)-the second longest chromosome. A review of other studies reveals the same distribution of NOR sites (putative rDNA loci) in three other species: on 10q in C. sikamea and C. angulata from the Pacific Ocean and on 2p in C. gasar from the western Atlantic. All data support the conclusion that differences in size and shape of the rDNA-bearing chromosome represent a major divide between Asian-Pacific and Atlantic species of Crassostrea. This finding suggests that chromosomal divergence can occur under seemingly conserved karyotypes and may play a role in reproductive isolation and speciation.

Topographic changes in nascent and early mesoderm in amphioxus embryos studied by Dil labeling and by in situ hybridization for a Brachyury gene

In amphioxus embryos, the nascent and early mesoderm (including chorda-mesoderm) was visualized by expression of a Brachyury gene (AmBra-2). A band of mesoderm is first detected encircling the earliest (vegetal plate stage) gastrula sub-equatorially. Soon thereafter, the vegetal plate invaginates. resulting in a cap-shaped gastrula with the mesoderm localized at the blastoporal lip and completely encircling the blastopore. As the gastrula stage progresses, DiI (a vital dye) labeling demonstrates that the entire mesoderm is internalized by a slight involution of the epiblast into the hypoblast all around the perimeter of the blastopore. Subsequently. during the early neurula stage, the internalized mesoderm undergoes anterior extension mid-dorsally (as notochord) and dorsolaterally (in paraxial regions when segments will later form). By the late neurula stage, AmBra-2 is no longer transcribed throughout the mesoderm as a whole; instead. expression is detectable only in the posterior mesoderm and in the notochord, but not in par axial mesoderm where definitive somites have formed.

Cloning and characterization of a novel C-type lectin from Zhikong scallop Chlamys farreri

C-type lectin is a family of Ca2+ dependent carbohydrate-recognition proteins which play crucial roles in the innate immunity of invertebrates by mediating the recognition of host cells to pathogens and clearing microinvaders as a pattern recognition protein (PRP). The cDNA of Zhikong scallop Chlamys farreri C-type lectin (designated CFLec-1) was cloned by expressed sequence tag (EST) and RACE techniques. The full-length cDNA of CFLec-1 was 1785 bp, consisting of a 5'-terminal untranslated region (UTR) of 66 bp and an unusually long 3' UTR of 1040 bp with seven polyadenylation signal sequences AATAAA and a poly(A) tail. The CFLec-1 cDNA encoded a polypeptide of 221 amino acids with a putative signal peptide of 15 amino acid residues and a mature protein of 206 amino acids. Analysis of the protein domain features indicated a typical long-form carbohydrate-recognition domain (CRD) of 130 residues in the CFLec-1 deduced amino acid sequence. The expression pattern of CFLec-1 transcripts in healthy and bacterial challenged scallops was studied by semi-quantitative RT-PCR. mRNA transcripts of CFLec-1 could be mainly detected in the tissues of haemocytes, gill, gonad and mantle of unchallenged scallops, whereas the expression of CFLec-1 transcripts was increased in all the tested tissues after heat-killed Vibrio anguillarum challenge. The temporal expression of CFLec-1 mRNA in haemolymph challenged by Micrococcus luteus and V anguillarum was both up-regulated and reached the maximum level at 8 and 16 It post stimulation, respectively, and then dropped back to the original level. In order to investigate its immune functions, CFLec- I was recombined and expressed in Escherichia coli BL21(DE3)-pLysS as a fusion protein with thioredoxin. The recombinant CFLec-1 agglutinated bacteria E. coli JM109 in vitro, and the agglutination was Ca2+ dependent which could be inhibited by EDTA. But it did not agglutinate M. luteus, Candida lipolytica and animal erythrocytes including rabbit, rat, mouse, chicken, human group A, human group B, human group O. Meanwhile, the recombinant CFLec-1 could inhibit the growth of both E. coli JM 109 and M. luteus, but no inhibition activity against V anguillarum. These result indicated that CFLec-1 was a constitutive and inducible PRP which was involved in the reorganization and clearance of invaders in scallop. (c) 2006 Elsevier Ltd. All rights reserved.

珠江口冲淡水扩展变化及机制研究

本文利用1978~1984年南海北部的逐月调查资料，分析珠江口冲淡水的扩展特征及其扩展变化。资料分析显示，在风及入海径流量等因素的影响下，珠江口冲淡水的扩展具有季节变化和年际变化。夏季珠江口冲淡水在河口外的扩展形态可划分出四种扩展形态，包括向海扩展型、粤东扩展型、粤西扩展型及似对称扩展型。同时根据珠江入海月平均流量与冲淡水扩展面积的相关分析可知，珠江口入海流量的大小决定了河口冲淡水在口外的扩展大小，流量的季节变化决定了冲淡水扩展大小的季节变化，而流量的年变化影响着冲淡水扩展的年变化。根据海域风场与冲淡水扩展形态的对比分析表明，风的季节变化和日变化影响着冲淡水扩展方向的变化，风场影响控制了珠江口冲淡水不同的扩展形态。夏季在E~SE向风的作用下，珠江口冲淡水扩展表现为粤西扩展型；而珠江口冲淡水扩展为粤东扩展型时，南海北部的月平均风场为SSW~SW向风。冲淡水扩展倾向于向海扩展型时，海域吹S风为主，且风速较小。 在资料分析的基础上，本文利用ECOM模式对冲淡水扩展的动力机制进行进一步探讨。模式试验结果表明，理想情况下，珠江河口冲淡水向外海突出，冲淡水扩展形态为向海扩展型；珠江入海流量的大小决定冲淡水扩展范围的大小，入海流量大，冲淡水扩展的范围大。不同方向的盛行风是珠江河口冲淡水扩展形态和动力的决定因子。在东北风、东风和东南风的作用下，河口冲淡水形态为粤西扩展型，风持续时间长，冲淡水扩展形态表现为极端粤西扩展型。在西南季风的影响下，河口冲淡水的扩展方向明显相反，冲淡水扩展形态表现为典型的粤东向离岸扩展型。S、SSE风约束了河口冲淡水向口外的扩展，冲淡水扩展形态表现为轻微的粤东向扩展。在偏E风与偏S风交替作用下，表层冲淡水在一定时刻会出现似对称形态。 在对南海北部潮汐潮流研究的基础上，本文进一步模拟了潮汐潮流对珠江口冲淡水扩展的影响。模型试验结果显示，珠江口周期性的潮流运动所造成的低盐水的净水平输运很小，其主要作用更多体现在对冲淡水与周围高盐水体的混合上，在很大程度上限制了低盐水向海或向两侧方向的扩展。 在模型试验的基础上，本文进一步模拟了在多种动力因子作用下夏季珠江口冲淡水的扩展演化规律。模式计算表明，珠江口冲淡水扩展形态的演变受多种因素影响，而风是其中影响冲淡水扩展演化最重要的因子。 将考虑斜压效应和不考虑斜压效应的模式计算结果进行比较，结果显示珠江口冲淡水扩展对粤东、粤西沿岸流的形成和发育影响明显。夏季珠江口冲淡水的扩展可促进粤东沿岸流的进一步发育，粤东沿岸流强化。而影响粤西沿岸流的主要因子是风应力和珠江口冲淡水的西向扩展，无风或弱风时，粤西西向流主要是由于冲淡水与周围水体的压力差所产生的密度流经过地转调整作用形成的；否则是SE~NE风与珠江口冲淡水的西向扩展同时影响粤西沿岸流的西向流动。

Formation of Fe-oxyhydroxides from the East Pacific Rise near latitude 13 degrees N: Evidence from mineralogical and geochemical data

The mineralogical and geochemical characteristics of Fe-oxyhydroxide samples from one dredge station (long. 103 degrees 54.48'W, lat. 12 degrees 42.30'N, water depth 2655 m) on the East Pacific Rise near lat 13 degrees N were analyzed by XRD, ICP-AES, and ICP-MS. Most Fe-oxyhydroxides are amorphous, with a few sphalerite microlites. In comparison with Fe-oxyhydroxides from other fields, the variable ranges in the chemical composition of Fe-oxyhydroxide samples are very narrow; their Fe, Si, and Mn contents were 39.90%, 8.92%, and 1.59%, respectively; they have high Cu (0.88%-1.85%) and Co (65x10(-6)-704x10(-6)) contents, and contain Co+Cu+Zn+Ni > 1.01%. The trace-element (As, Co, Ni, Cu, Zn, Ba, Sr) and major-element (Fe, Ca, Al, Mg) contents of these samples are in the range of hydrothermal sulfide from the East Pacific Rise near 13 degrees N, reflecting that this type of Fe-oxyhydroxide constitutes a secondary oxidation product of hydrothermal sulfide. The Fe-oxyhydroxide samples from one dredge station on the East Pacific Rise near 13 degrees N are lower in Sigma REE (5.44x10(-6)-17.01x10(-6)), with a distinct negative Ce anomaly (0.12-0.28). The Fe-oxyhydroxide samples have similar chondrite-normalized rare-earth-element (REE) patterns to that of seawater, and they are very different from the REE composition characteristics of hydrothermal plume particles and hydrothermal fluids, showing that the REEs of Fe-oxyhydroxide are a major constituent of seawater and that the Fe-oxyhydroxides can become a sink of REE from seawater. The quick settling of hydrothermal plume particles resulted in the lower REE content and higher Mn content of these Fe-oxyhydroxides, which are captured in part of the V and P from seawater by adsorption. The Fe-oxyhydroxides from one dredge station on the East Pacific Rise near 13 degrees N were formed by secondary oxidation in a low temperature, oxygenated environment. In comparison with the elemental (Zn, Cd, Pb, Fe, Co, Cu) average content of hydrothermal sulfide samples from the East Pacific Rise near 13 degrees N, the Zn, Cd, and Pb contents of the Fe-oxyhydroxides are lower, and their Fe, Co, and Cu contents are higher.

栉孔扇贝凝集素家族基因研究

栉孔扇贝是我国北方重要的贝类养殖品种。自1997年以来爆发的栉孔扇贝大规模死亡，给地区经济造成了重大损失并且已经严重威胁扇贝养殖业的健康发展。然而，到目前为止，对扇贝免疫防御的分子机理了解还很少，深入研究扇贝免疫应答的分子机制是认识和了解病害发生和实现病害控制的关键问题之一。本研究采用了EST大规模测序结合cDNA锚定扩增的方法，从栉孔扇贝cDNA文库中克隆到五个C－型凝集素基因，并对其中部分基因进行了深入研究。 C－型凝集素CFLec－1的基因全长1785bp，其中含有5’非翻译区66bp，随后是666bp的开放阅读框；最后一条非常长的3’非翻译区1040bp，其中包含多个多聚腺甘酸加尾信号和polyA尾巴。栉孔扇贝CFLec－1编码221个氨基酸的蛋白，其N末端为15个氨基酸的信号肽。CFLec－1的成熟肽为206个氨基酸，其等电点为5.12，计算分子量为23.49kDa。SMART程序分析显示，C末端130氨基酸是一个标准的长型C－型凝集素结构域，其中四个半光胺酸（Cys104，Cys177，Cys193，Cys202）形成的两对二硫键维持了C－型凝集素的空间结构，而位于N末端的两个二硫键（Cys74，Cys85）构成了长型C－型凝集素结构域特有的一对额外二硫键。同源性分析表明，CFLec－1的C－型凝集素结构域与红原鸡的甘露糖受体中的C－型凝集素结构域有47％的相似度，与大西洋鲑的C－型凝集素受体C有31％的相似度。通过与其他同源的C－型凝集素结构域序列比对，发现了可能的糖结合位点EPD基域（Glu169-Pro170-Asp171）。通过RT－PCR研究CFLec－1在扇贝不同组织中的分布后发现，在健康扇贝中，CFLec－1在性腺中有中等程度的表达，在腮中有少量表达，在血淋巴和外套膜中有微量表达。经热处死的鳗弧菌刺激后，CFLec－1在几乎所有检测组织中的表达量都有明显的提高，其中，血淋巴中的表达量变化最为显著。这些结果说明CFLec－1是组成/诱导型基因，并且可能参与了黏膜防御。通过RT－PCR分析了CFLec－1在血淋巴中的表达特征后发现，在革兰氏阳性菌溶壁微球菌和革兰氏阴性菌鳗弧菌刺激后，CFLec－1的表达均显著高于对照组，并且成明显的随时间变化趋势。在大肠杆菌中表达的重组CFLec－1可以凝集革兰氏阴性菌大肠杆菌JM109，且凝集过程需要钙离子的参与。重组CFLec－1对大肠杆菌JM109有较弱的抑菌活性，对溶壁微球菌有明显的抑菌活性，对鳗弧菌没有抑菌活性。这一结果说明，CFLec－1可能不仅参与对入侵微生物的识别过程，而且可能作为效应分子起到了直接杀灭入侵微生物的作用。 CFLec-2的cDNA全长为708bp，其5’UTR为59bp。3’UTR为217bp。 CFLec-2的开放阅读框为432bp，编码160个氨基酸残基,其中包含5’信号肽17个残基。CFLec-2的编码区中含有一个C-型凝集素结构域。利用本研究中构建的原核表达载体，CFLec-2的成熟肽在大肠杆菌中被成功表达。 mCFLec-1的cDNA全长为2257bp，5’UTR17bp，3’UTR为713bp。mCFLec-1的开放阅读框为1527bp，编码508个氨基酸残基，其中包含17个氨基酸残基的信号肽序列。mCFLec-1的编码区含有三个串联的C-型凝集素结构域。利用本研究中构建的原核表达载体，mCFLec-2的成熟肽在大肠杆菌中被成功表达。 mCFLec-2的cDNA全长2086bp。其5’UTR长为18bp，3’UTR长为238bp。开放阅读框均为1776bp，编码609个氨基酸残基，其中包含N末端由18个氨基酸构成的信号肽。mCFLec-2的编码区包含四个C-型凝集素结构域。mCFlec-3的cDNA全长1897bp，其5’UTR和编码区与mCFLec-2几乎完全相同，只有个别碱基的差异。mCFlec-3的3’UTR为49bp。 本研究从扇贝机体本身的免疫机制入手，深入探讨其免疫机理，为进一步研究信号传导，了解扇贝先天性免疫的机制，为制定合理的研制策略提供坚实的理论基础；丰富和发展海水无脊椎动物免疫学的内容，为控制养殖生物疾病提供了新的思路；进一步通过高低等生物之间功能类似分子的同源性比对，为解释和阐明先天免疫这种已经存在数十亿年，从低等生物开始到人类仍旧保留且更加完善的免疫系统的奥秘和本质提供证据。

中国近海沉积物中黑碳和多环芳烃的研究

黑碳和多环芳烃都是燃烧产生的污染物，并广泛存在于土壤及海洋特别是近海沉积物中。由于黑碳和多环芳烃对环境及生态系统具有不同的影响途径和危害，多年来一直受到环境研究者的极大重视。本文对我国近海几个海区（渤海湾、北黄海、胶州湾、南海珠江口及其邻近海区）沉积物中黑碳和多环芳烃的含量、分布及来源进行了研究，并首次对各海区表层沉积物中黑碳和多环芳烃的相关性进行了分析。 数据显示，中国近海各海区（渤海湾、北黄海、胶州湾、南海珠江口及其邻近海区）表层沉积物中黑碳的浓度范围为0.1 - 2.45 mg/gdw，占总有机碳浓度的1 - 41%，具有较大的空间差异。渤海湾表层沉积物中黑碳浓度最高（平均为2.18 mg/gdw），占沉积物中总有机碳浓度的27 - 41%。相比之下，北黄海、胶州湾和南海珠江口及其邻近海区表层沉积物中黑碳浓度较低，分别占沉积物中总有机碳浓度的6%、8%和5%。黑碳的分布主要受其来源的影响，陆地来源和河流输入是中国近岸海区表层沉积物中黑碳的重要来源。该研究显示黑碳在沉积物中的埋藏可能代表我国近海各海区碳循环中的一个重要碳汇。 中国近海各海区（渤海湾、北黄海、南海珠江口及其邻近海区）表层沉积物中多环芳烃的浓度范围为47.5 – 3673.5 ng/g（均为干重），亦具有很大的空间差异。渤海湾中多环芳烃的浓度最高（82.9 – 3673.5 ng/g），反映了该地区受人类污染严重的特征。在三个海区表层沉积物中，单组分多环芳烃的分布也具有明显不同的特征，渤海湾主要以5、6环的多环芳烃为主，而北黄海和南海珠江口及其邻近海区3、4环多环芳烃的浓度较高。基于多环芳烃的单组分分布特征和一些特殊指数，可以得到渤海湾表层沉积物中的多环芳烃以木材、煤的不完全燃烧来源为主，而北黄海海区和南海珠江口及其邻近海区的多环芳烃显示出木材、煤的燃烧和石油燃烧的混合来源。 中国近海表层沉积物中黑碳浓度与多环芳烃的浓度并不存在很好的相关性，这说明中国近海表层沉积物中的黑碳和多环芳烃具有不同的来源，且在沉积物中的埋藏受控于不同的地球化学作用。

Growth characters and photosynthetic capacity of Gracilaria lemaneiformis as a biofilter in a shellfish farming area in Sanggou Bay, China

Experiments on growth characters and ecological functions of the macroalgae Gracilaria lemaneiformis, collected from south China, were conducted in polyculture areas of kelp and filter-feeding bivalve in Sanggou Bay in Weihai City, Shandong, in north China from May 2002 to May 2003. The results of 116 days cultivation showed that the average wet weight of alga increased 89 times from 0.1 to 8.9 kg rope(-1), with an average specific growth rate ( based on wet weight) of 3.95% per day. The most favorable water layer for its growth was 1.0 - 1.8 m below the surface in July and August, with an average specific growth rate of 8.2% per day in 30-day experiments. Photosynthetic activity changed seasonally, with an average of 7.3 mg O-2 g dw(-1) h(-1). The maximum rate (14.4 mg O-2 g dw(-1) h(-1)) was recorded in July, or 19.3 mg CO2 g dw(-1) h(-1), while the minimum (0.40 mg CO2 g dw(-1) h(-1)) was in April. This study indicated that the culture of G. lemaneiformis is an effective way to improve water quality where scallops are cultivated intensively.

Antimicrobial screening and active compound isolation from marine bacterium NJ6-3-1 associated with the sponge Hymeniacidon perleve

Twenty-nine marine bacterial strains were isolated from the sponge Hymeniacidon perleve at Nanji island, and antimicrobial screening showed that eight strains inhibited the growth of terrestrial microorganisms. The strain NJ6-3-1 with wide antimicrobial spectrum was identified as Pseudoalteromonas piscicida based on its 16S rRNA sequence analysis. The major antimicrobial metabolite, isolated through bioassay-guide fractionation of TLC bioautography overlay assay, was identified as norharman (a beta-carboline alkaloid) by EI-MS and NMR.

Kiitricha minuta n. Sp., a peculiar hypotrichous ciliate (Ciliophora, Spirotrichea) from the Yellow Sea

The morphology and infraciliature of a new ciliate, Kiitricha minuta n. sp., isolated from the Yellow Sea, were investigated using live observation and protargol impregnation. Kiitricha minuta represents a third member of the rarely known order Kiitrichida. It is unique in the subclass Hypotrichia in having many rows of small uniform cirri along the right side of the body and the dorsal kineties composed of dikinetids, most of which bear two cilia. Kiitricha minuta n. sp. is ovoid and measures about 60 x 45 mu m in vivo. It has a huge buccal cavity occupying about 80% of the body length, numerous body extrusomes, one macronucleus and two micronuclei, 27-27 adoral membranelles, 9-12 frontoventral cirral rows, a submarginal row of 7-9 cirri, 6 or 7 transverse cirri, and roughly 7-9 dorsal kineties. This new species differs distinctly from its only congener Kiitricha marina by its smaller size (60 mu m vs. 80-150 mu m), the presence of body extrusomes (vs. absent), the different macronuclear pattern (one vs. two nodules), and the lower number of frontoventral cirral rows (9-12 vs. 21-26), which terminate at the anterior two-thirds of body (vs. extend to the posterior). The new term "submarginal cirral row" is introduced to distinguish from the marginal cirral row in typical hypotrichs sensu lato. Based on our new observations and the literature, an improved diagnosis for the genus Kiitricha is provided and its phylogenetic importance is discussed.

Bromophenols coupled with methyl gamma-ureidobutyrate and bromophenol sulfates from the red alga Rhodomela confervoides

Four new bromophenols C-N coupled with methyl gamma-ureidobutyrate (1-4), a phenylethanol bromophenol (5), and three phenylethanol sulfate bromophenols (6-8) have been isolated from polar fractions of an ethanolic extract of the red alga Rhodomela confervoides. On the basis of spectroscopic evidence including HRMS and 2D NMR data, the structures of the new compounds were determined as methyl N'-(2,3-dibromo-4,5-dihydroxybenzyl)-gamma-ureidobutyrate (1), methyl N,N'-bis(2,3-dibromo-4,5-dihydroxybenzyl)-gamma-ureidobutyrate (2), methyl N'-[3-bromo-2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxybenzyl]-gamma-ureidobutyrate (3), methyl N'-(2,3-dibromo-4,5-dihydroxybenzyl)-A7-[3-bromo2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxybenzyl]-gamma-ureidobutyrate (4), 2,3-dibromo-4,5-dihydroxyphenylethanol (5), 2,3-dibromo-4,5-dihydroxyphenylethanol Sulfate (6), 3-bromo-4,5-dihydroxyphenylethanol sulfate (7), and 3-bromo2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxyphenylethanol sulfate (8). The cytotoxicity of all compounds was evaluated against several human cancer cell lines including human colon cancer (HCT-8), hepatoma (Bel7402), stomach cancer (BGC-823), lung adenocarcinoma (A549), and human ovarian cancer (A2780). Among them, the phenylethanol and the phenylethanol sulfate bromophenols (5-8) showed moderate cytotoxicity against all tested cell lines.

藏药薰倒牛的化学成分研究

目的:研究传统藏药薰倒牛Biebersteinia heterostemon的化学成分.方法:运用正相及反相硅胶柱色谱分离纯化,采用现代波谱与X-ray单晶衍射等方法鉴定化合物的结构.结果:从全草中分离纯化出3个化合物,其结构分别鉴定为山羊豆碱(galegine,1),顺式-4-羟基山羊豆碱(cis-4-hydroxygalegine,2),反式-4-羟基山羊豆碱(trans-4-hydroxygalegine,3).其中化合物3的结构还得到X-ray单晶衍射的证实.结论:化合物1～3均为首次从该植物中分离得到.

氮杂环荧光试剂2-(11H-苯[a]咔唑)乙基氯甲酸酯对胺类化合物标记及质谱鉴定

含氮类荧光试剂2-(11H-苯[a]咔唑)乙基氯甲酸酯 (BCEC-Cl) 经柱前衍生处理后,采用荧光检测及柱后在线质谱鉴定对食品中胺类化合物进行了测定.标记反应在pH 9的硼酸缓冲液中进行,3 min后获得稳定的荧光产物.衍生物于λex＝279 nm激发条件下产生强烈荧光,其发射波长在λem＝380 nm处.产物的分离在Eclipse XDB-C8色谱柱 (150 mm×4.6 mm,5 μm)上进行,采用梯度洗脱对12种脂肪胺衍生物进行了优化分离.采用大气压化学电离源(APCI Source)正离子模式进行在线的柱后质谱鉴定,实现了多种脂肪胺衍生物的快速、准确测定.建立的方法具有良好的重现性,回归系数大于0.9996,检出限为1.8～14 fmol.

藏羚羊冷季对干物质的消化效率

藏羚羊(Pantholops hodgsoni)为青藏高原特有物种,也是世界上最为珍贵和稀有的物种之一.作为青藏高原野生食草动物的典型代表,藏羚羊种群也是构成青藏高原自然生态系统极为重要的组成部分

A New Triterpenoid from Amoora dasyclada

Five compounds were isolated from the EtOH extraction of the stem of Amoora dasyclada (How et T. Chen) C. Y. Wu (Meliaceae). On the basis of spectroscopic methods, their structures were elucidated as 24, 25-epoxy-tirucall-7-ene-3, 23-dione (1), 24, 25, 26, 27-tetranortirucall-7-ene-3-oxo-23(21)-lactone (2), taraxerone (3), taraxerol (4) and b-sitosterol (5). Among them, compound 1 was a new triterpenoid, compounds 3-5 were firstly obtained from this plant; compound 2, an tetranortriterpenoid, was firstly isolated from natural sources, and its NMR data were assigned for the first time. Moreover, the D7-bond and the Me-14 in compound 2 were never changed, which has never been found in other tetranortriterpenoids. And the biosynthetic pathway of tetranortriterpenoid was further discussed.