共查询到20条相似文献，搜索用时 76 毫秒
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从竹叶中提取黄酮和多糖,用抑制亚硝酸盐显色的方法测定了竹叶黄酮和多糖清除亚硝酸盐的作用,并同Vc比较。结果：竹叶黄酮对亚硝酸盐有较强的清除率,剂量从0.1mg增加到4.0mg,清除率从15.72±1.83（%）增加到84.59±1.16（%）,量效之间呈线性关系（r=0.9649）;剂量再增加到5.0mg,清除率不再显著增加（P〉0.5）。竹叶多糖对亚硝酸盐也有一定的清除率,剂量从0.1mg增加到3.0mg,清除率从8.55±0.46（%）增加到36.10±0.61（%）,量效之间呈较好的线性关系（r=0.9789）;剂量再增加到4.0mg和5.0mg,清除率并不再增加（P〉0.4）。Vc对亚硝酸盐的清除率相当高,0.1mg剂量的清除率即达到61.24±6.31（%）,剂量增加到1.0mL时清除率已达到100%,清除率随剂量增加的曲线似抛物线形。Vc对亚硝酸盐的清除率均显著高于同剂量的竹叶黄酮和竹叶多糖（均P〈0.001）。 相似文献
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研究桂花黄酮抗自由基作用及体内抗氧化功能。通过测定桂花黄酮对羟自由基清除率和超氧阴离子自由基的抑制率实验,研究桂花黄酮的体外抗氧化作用;通过测定小鼠血清GSH-Px、SOD活性和MDA含量的变化,研究桂花黄酮体内抗氧化作用。结果表明,桂花黄酮可有效地清除羟自由基、超氧阴离子自由基,桂花黄酮可显著增强小鼠血清GSH-Px、SOD活性,降低MDA含量。结论:桂花黄酮具有一定的体内外抗氧化作用。 相似文献
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夏铁骑 《濮阳职业技术学院学报》2010,23(6)
通过测定羟基自由基(·OH)的清除率和猪油的过氧化值研究了苦瓜黄酮的抗氧化活性.结果表明:苦瓜中黄酮类物质的提取率为1.3297%,苦瓜黄酮清除羟基自由基时存在良好的量效关系且呈线性关系,其IC50为0.37mg/ml;当苦瓜黄酮的添加量为0.08%时.其对猪油的抗氧化作用接近TBHQ. 相似文献
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目的:优化沙棘中总黄酮提取工艺,明确其抗氧化性能。方法:以沙棘为研究对象,以沙棘黄酮得率为指标值,使用乙醇溶液作为提取剂,采用超声波辅助萃取法,对提取时间(A)、提取温度(B)、乙醇体积分数(V乙醇/V_总)(C)、料液比(D)进行单因素试验和响应面分析,考察4个因素对总黄酮得率的影响,并对沙棘黄酮的体外抗氧化活性进行检测。结果:在提取时间23 min、提取温度80℃、50%乙醇、料液比1∶20条件下沙棘黄酮得率最高,为2.316 mg/g。各因素对沙棘黄酮得率的影响大小依次为：料液比、乙醇体积分数、提取时间、提取温度。体外抗氧化结果表明,沙棘黄酮具有很好的DPPH自由基和羟自由基清除能力,当沙棘黄酮粗提取物质量浓度达到5 mg/mL时,沙棘黄酮对DPPH自由基的清除率达87.5%,对羟自由基的清除率达到了77.7%。结论:沙棘中含有丰富的黄酮类物质,且具有较好的抗氧化性能。 相似文献
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采用超声提取法从丝瓜皮中提取黄酮,通过正交试验确定最佳提取条件:超声时间20 min、料液比1:12、乙醇体积分数70%,在此条件下黄酮提取率为1.96%.通过测定丝瓜皮提取物对羟基自由基和超氧离子自由基的清除率,表明其具有较高的抗氧化能力. 相似文献
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酸雨对植物的危害,已为人们所共识.通过人工模拟酸雨实验,可进一步探讨酸雨 的低PH值（PH值由7.0下降到2.0）会使植物的叶细胞透性增加（叶细胞透性增加的百分率（ %）：青菜最大可达到214.2%,莴苣可达到136.23%）．同时也会使植物叶片中的叶绿素含量 下降（青菜的叶绿素含量从0.851mg/g·鲜重下降到0.247mg/g·鲜重,莴苣的叶绿素含量从 0.868mg/g·鲜重下降到0.185mg/g·鲜重）．进而影响植物的生长发育,对植物造成伤害． 相似文献
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采用超声波法从仙人掌中提取黄酮类化合物,并用流动注射化学发光法测定了仙人掌的抗氧化性能.结果：方法的回收率为94.0%~109.0%,变异系数小于0.30%.测得仙人掌中黄酮化合物的含量为1.53 mg/g,仙人掌的IC50为1.38 mg/mL.结果表明,仙人掌的黄酮含量较高且具有较强的抗氧化性能. 相似文献
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对芹菜不同部位黄酮化合物进行提取,采用光谱法对其含量进行分析.测定波长为510 nm,线性范围为0.2557～0.7670 mg/mL,方法的回收率为101.5％～104.6％,变异系数小于0.27％.用流动注射化学发光法分析了芹菜不同部位的抗氧化性,实验结果表明芹菜中含有丰富的黄酮类化合物.芹菜不同部位中黄酮化合物含量不同,芹菜叶中黄酮含量最高,芹菜根中黄酮含量次之,而芹菜茎中黄酮含量最低.芹菜具有较强的抗氧化性,芹菜不同部位抗氧化性不同,芹菜叶的抗氧化性最强,芹菜根次之,而芹菜茎中抗氧化性最低.芹菜不同部位即根、茎、叶中黄酮类化合物含量与抗氧化性增加趋势相同.芹菜根、茎、叶的黄酮含量与抗氧化性呈现明显的量效关系. 相似文献
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毛善国 《南京晓庄学院学报》2012,(6):77-80
该实验研究不同浓度的锌对小麦幼苗叶片光合特性的影响.实验结果表明,小麦幼苗叶片叶绿素含量在在处理浓度为2.0 mg/L时比对照组增加了10.17%,荧光动力学参数NPQ的值在处理浓度为5.0 mg/L时比对照组增加了34.31%,ETR的值在处理浓度为3.0 mg/L时比对照组增加了26.18%,qP和φPSⅡ的值在处理浓度为5.0 mg/L时分别降低24.17%和27.47%.但锌处理对小麦幼苗荧光动力学参数中Fv/Fm和Fv’/Fm’的值的影响不显著. 相似文献
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建立黑果腺肋花楸果制剂中有效成分的含量测定方法,并对制剂清除亚硝酸盐的能力、抑制脲酶、α-葡萄糖苷酶、胰脂肪酶的活性进行考察.采用紫外-可见分光光度法对颗粒剂中的总黄酮、原花青素、花色苷和多糖进行含量测定及方法学验证;用半数浓度(IC50值)作为指标来评价颗粒剂的不同体外活性.实验结果表明,两种颗粒剂均在显色前360 min内和显色后60 min内有良好的稳定性,重复性和精密度良好,加样回收率为98.63%～102.50%和98.27%～103.00%,且RSD<2.0%,建立的方法可满足含量测定要求.3批黑果颗粒剂和双果颗粒剂中总黄酮、原花青素、花色苷、多糖的含量平均值分别为7.27、14.10、1.56、473.95 mg/g和12.35 mg/g、3.44 mg/g、0.80 mg/g、700.12 mg/g.体外活性实验表明两种颗粒剂均具有一定的清除亚硝酸盐能力,抑制脲酶、α-葡萄糖苷酶和胰脂肪酶活性的能力.且建立的4类有效成分的含量测定方法,具有较好的重复性,回收率符合要求,可用于黑果腺肋花楸果制剂中总黄酮、原花青素、花色苷、多糖的含量测定,能为评... 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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唐芳 《读与写:教育教学刊》2008,5(6)
During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context. 相似文献