共查询到20条相似文献，搜索用时 390 毫秒
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刘艳芳 《赤峰学院学报(自然科学版)》2014,(1):84-85
糖苷生物碱主要分布在茄科及百合科的一些植物体内,由疏水性的苷元和亲水性的寡糖链构成,是一种甾体皂苷.苷元为螺旋甾碱烷、茄次碱烷和其他甾体衍生物3类,寡糖链由3~4个单糖组成.植物合成糖苷生物碱主要是为了防御微生物、动物及昆虫的侵袭,具有一定毒性,但与此同时,它还具有降低胆固醇、消炎、活血镇痛、增强机体免疫力、协同、抗病原微生物、抗癌等多种生理活性.关注糖苷生物碱的结构、活性、毒性三者的关系,对糖苷生物碱的毒性机制及活性进一步探讨,必将成为日后其研究的重要突破口,亦为天然药物及保健食品行业的发展奠定重要的理论基础. 相似文献
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目的:建立从铜耐性植物海州香薷地上部提取分离芹菜素糖苷的工艺技术,探索铜耐性植物海州香薷资源化途径。创新点:结合使用大孔树脂、凝胶树脂、聚酰胺树脂多种色谱柱技术,从铜耐性植物海州香薷中提取分离纯度达98%的黄酮苷类化合物芹菜素糖苷。方法:以铜耐性植物海州香薷为原料,用60%乙醇溶液浸提,提取液依次使用石油醚、乙酸乙酯、饱和正丁醇萃取。实验中,对饱和正丁醇萃取层,使用D101型大孔吸附树脂粗分离提取,Sephadex?LH-20型凝胶筛分分离,并借助半制备液相和聚酰胺树脂分离纯化,得到芹菜素糖苷单体(图1)。利用紫外光谱、液相色谱–质谱联用、红外光谱、一维和二维核磁图谱,鉴定芹菜素糖苷结构(图2~5)。结论:芹菜素糖苷是铜耐性植物海州香薷体内的天然产物,利用色谱技术可以从海州香薷植物体中分离出芹菜素糖苷单体。 相似文献
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天然植物多糖及复合多糖的研究进展 总被引：2，自引：0，他引：2
娜日苏 《赤峰学院学报(自然科学版)》2009,25(1):68-72
天然植物多糖是由十个以上的单糖通过苷键连接而成的聚合物,它们除了作为植物的贮藏养料和骨架成分外,还具有免疫调节,抗肿瘤、抗衰老、降血糖、抗凝血等作用,且对机体的毒副作用小.现对天然植物多糖的提取,分离纯化,纯度鉴定,生物活性及复合多糖的研究进展进行综述,为其未来的相关研究提供参考. 相似文献
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长期以来,人们认为细胞壁的作用仅仅是决定细胞的大小、形状和韧性。10多年前,Ayers等发现一种真菌细胞壁中释放出具有寡聚葡苷结构的分子,它能诱导这种真菌的宿主产生植物抗菌毒素。此后不久,科学家又相继发现受伤的菜豆等植物的细胞壁能释放寡糖片断,称寡糖素,对于植物的抗逆性、生长速度、形态发生等方面具有调节功能。寡糖素与细胞壁中的纤维素结构无关,仅与果胶或半纤维素有关,多为寡聚半乳糖苷醛酸。现将其功 相似文献
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大豆异黄酮为大豆中的非营养成分 ,近来的研究发现 ,大豆黄酮具有抗癌抗氧化及雌激素样作用 .能够降血脂 ,抑制动脉粥样硬化形成和改善骨化谢[1] 。另外 ,对脑卒中 ,糖尿病及肾病也有一定的影响[2 ] ,本文仅对大豆黄酮的抗癌作用加以综述 .异黄酮的糖苷配基在肠道细菌葡萄糖苷酶的作用下脱离释放出有生物活性的三羟异黄酮 ( ｇｅｎｉｓｔｅｎ ,染料木黄酮 )二羟异黄酮(ｄａｉｄｚｅｉｎ ,黄豆苷原 )和 6-甲氧基大豆素 ( ｇｌｙｃｉｔｅｉｎ)。它们在成人体内可被肠道细菌进一步转化为雌马酚 (ｅｐｕｏｌ )对乙苯酚 ( ｐ -ｅｔｈｙｌｐｈｅｎ… 相似文献
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缩氨基硫脲类化合物具有广泛的生物活性,在医药、农药中起着越来越重要的作用,综述了有关缩氨基硫脲化合物的合成、生物活性研究方面的工作。 相似文献
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N-保护的氨基醇是生物活性药物和天然产物合成中的重要中间体。采用价廉易得的NaBH_4-I_2-THF体系还原N-Cbz或Boc保护的脯氨酸,可以得到相应的脯氨醇,反应条件温和,产率高,化学选择性好,保护基不受影响。 相似文献
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Evaluation of the hepatoprotective and antioxidant activities of Rubus parvifolius L 总被引：1，自引：0，他引：1
Gao J Sun CR Yang JH Shi JM Du YG Zhang YY Li JH Wan HT 《Journal of Zhejiang University. Science. B》2011,12(2):135-142
The hepatoprotective and antioxidant activities of the n-butanol extract of Rubus parvifolius L. (RPL), a widely used medicinal plant, were evaluated. Results demonstrated that RPL extract possessed pronounced hepatoprotective
effects against carbon tetrachloride (CCl4)-induced hepatic injury in mice, which was at least partially attributed to its strong antioxidant capacity. Treatment with
RPL extract markedly attenuated the increases in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST)
levels caused by CCl4 intoxication. It also significantly prevented the decrease in superoxide dismutase (SOD) activity and the increase in malondialdehyde
(MDA) content of liver tissue. Meanwhile, histopathological changes of hepatic damage were also remarkably ameliorated. Phytochemical
analysis based on high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) revealed the presence of various
phenolic compounds, including caffeic acid conjugates, ellagic acid glycosides, and flavonol glycosides, which might be responsible
for the hepatoprotective and antioxidant activities of RPL. 相似文献
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Leilani A. Arthurs Bailey Zo Kreager 《International Journal of Science Education》2013,35(15):2073-2091
ABSTRACTEngaging students in active learning is linked to positive learning outcomes. This study aims to synthesise the peer-reviewed literature about ‘active learning’ in college science classroom settings. Using the methodology of an integrative literature review, 337 articles archived in the Educational Resources Information Center (ERIC) are examined. Four categories of in-class activities emerge: (i) individual non-polling activities, (ii) in-class polling activities, (iii) whole-class discussion or activities, and (iv) in-class group activities. Examining the collection of identified in-class activities through the lens of a theoretical framework informed by constructivism and social interdependence theory, we synthesise the reviewed literature to propose the active learning strategies (ALSs) model and the instructional decisions to enable active learning (IDEAL) theory. The ALS model characterises in-class activities in terms of the degrees to which they are designed to promote (i) peer interaction and (ii) social interdependence. The IDEAL theory includes the ALS model and provides a framework for conceptualising different levels of the general concept ‘active learning’ and how these levels connect to instructional decision-making about using in-class activities. The proposed ALS model and IDEAL theory can be utilised to inform instructional decision-making and future research about active learning in college science courses. 相似文献
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采用蒸馏水回流浸提法从田七、绿茶、野菊花中提取其活性成分(主要有苷类,糖类、醇、酮、酯和多酚类活性成分),辅以薄荷等配制出具有清新口腔、抗炎、止血、清热解毒、消肿、减少牙菌斑、抑制龋菌功效的漱口水。将配制出的样品与国际品牌样品对照测定其口感、抑菌及稳定性等性能。结果表明:所配制的样品在抑菌性能方面优于市售产品。 相似文献
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Dabae Lee Anastasia S. Morrone Greg Siering 《Educational technology research and development : ETR & D》2018,66(1):95-127
To promote student learning and bolster student success, higher education institutions are increasingly creating large active learning classrooms to replace traditional lecture halls. Although there have been many efforts to examine the effects of those classrooms on learning outcomes, there is paucity of research that can inform the design and implementation process. This study investigates how spatial and technological features of a large collaborative classroom support active learning based on the Pedagogy-Space-Technology framework. The findings from our study suggest short lecture and class-wide discussion are essential in framing learning content before group activities, and connecting group outputs to the learning content after group activities. Through interviews, surveys, and focus groups, we found that-while small group activities are generally well-supported in large active learning classroomsfacilitating short lecture and class-wide discussion is key to the success of active learning in large classrooms. Technology should be carefully laid out in the space to accommodate those activities. Specific design and implementation suggestions and implications are provided. 相似文献
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幼儿的早期社会性发展对其一生的发展至关重要。针对目前幼儿社会发展中存在的种种问题与区域活动开展现状中的弊端,对跨班区域活动这一新的区域活动方式进行探究,认为跨班区域活动的开展,对幼儿的环境适应能力、主动交往意识和自主活动兴趣等方面都有积极的促进作用。 相似文献
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Leonard L. Baird 《Research in higher education》1990,31(3):271-278
Item and scale responses of students in 42 colleges to the College Student Experiences Questionnaire were examined to determine the frequency with which students had engaged in a wide variety of college activities. Results suggested that students most commonly attended and carried out activities related to studying and classwork, but typically did not engage in a great many intellectual and extracurricular activities. Students in selective and general liberal arts colleges were more active and involved in their colleges' lives than students in doctoral universities or comprehensive colleges and universities. Community college students were just as active as other students in academic areas, but were far less involved in out-of-class activities. 相似文献
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The effect of activity type on the engagement and interaction of young children with disabilities in inclusive childcare settings 总被引：1，自引：0，他引：1
The engagement and adult and peer interaction of 37 young children with a range of disabilities was measured in free play, group, and meal-routine activities in inclusive childcare settings. A significant effect for activity type was found for total engagement, active engagement, and passive engagement, with the children being more engaged in free-play and meal-routine activities than group activities. Free-play and meal-routine activities provided better opportunities for active engagement than did group activities, but children were more actively engaged during meal-routine activities than during free play. Passive engagement was more commonly observed during group activities. Children interacted more with their peers during free play. When children with a diagnosis of autism spectrum disorder were compared with children with other disabilities, they were found to be significantly less engaged during free play and interacted less with their peers. The implications of these findings for inclusive practice in childcare settings are discussed. 相似文献
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Astrid Nyquist Thomas Moser Reidun Jahnsen 《International Journal of Disability, Development & Education》2016,63(3):334-356
This study investigates the preferences for actual participation in and enjoyment of physical out-of-school activities in children with physical disabilities, including what particular activities they are actually participating in, how often, with whom, where, and how enjoyable they find these activities. The data are based on structured interviews with 149 children (67 girls (45%) and 82 boys (55%) from 6 to 17 years) who were attending three weeks of intensive rehabilitation at Beitostølen Healthsports Centre in Norway. The Children’s Assessment of Participation and Enjoyment and Preferences for Activities of Children scales were administered at the start of their rehabilitation stays. The study reveals a quite high level of participation in physical activity and a high degree of enjoyment in participating, but the children want to be even more active than they already are. They have clear preferences for activities, and these activities are to a large extent consistent with what they actually do during their leisure time. The children are most frequently active with family members, but they would prefer to be more active with peers. A prerequisite would therefore be to acquire better basic skills and competencies in a few chosen activities rather than having some experiences in a broad range of different activities. There are more similarities than differences between boys and girls and between age groups on the parameters investigated in this study. 相似文献
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Christine Stephen Jennifer Ellis Joan Martlew 《International Journal of Early Years Education》2010,18(4):315-329
This paper examines the extension of active learning pedagogical practices familiar in preschool settings to the first class of primary school. Policy and practice guidance in the UK is advocating the benefits of experiential learning as a way of engaging young children as they move into primary school but for teachers this means a move to new practices which can be in tension with other expectations. In this paper, the rationale for active learning is considered along with an account of the classroom activities of teachers and children in five primary schools that were implementing the policy shift to active learning. The children in these classes spent varying amounts of time in whole class activities led by the teacher or in small groups directed to engage with specific activities. They had opportunities to engage and respond verbally, through manipulating objects and with physical actions but the emphasis was on planned, teacher-directed learning activities. The characteristics of active learning as introduced in these innovative classes are compared with the expectations of practice guidance and theorising about early learning. 相似文献
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建构主义学习理论认为：学习过程是人的认知思维活动的主动建构的过程，是人们通过原有的知识经验与外界环境进行交互活动以获取、建构新知识的过程，学习者不是知识的被动接受者，而是知识的主动建构者；教师不再是教学内容的传递者，而是教学活动的组织者；学生也不再是教学内容的被动接受者，而是知识的主动获取与建构者，教师从以教授知识为主变为以指导、辅导学生的学习为主。教学过程不再是一个同步的，而是一个异步的、发散式的思维过程。 相似文献