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茉莉清茶中咖啡因的测定 总被引:2,自引:0,他引:2
[目的]建立一种快速、简单、准确的茉莉清茶中咖啡因的测定方法。[方法]用三氯甲烷萃取茉莉清茶中的咖啡因,在276.5 nm波长下有最大吸收,其吸收值的大小与咖啡因浓度成正比,从而可定量。[结果]不必沉淀蛋白质,直接测定茉莉清茶中的咖啡因,咖啡因含量在0~20μg/mL浓度范围内有良好的线性关系,相关系数r=1.000 0,相对标准偏差(RSD)为1.11%,回收率为94.8%~95.9%。[结论]不必沉淀蛋白质,直接用三氯甲烷萃取茉莉清茶中咖啡因的方法,操作简单,能满足分析要求。 相似文献
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[目的]比较市售4种绿茶和发酵茶(包括红茶、滇红茶和普洱茶)的茶多酚组成和比例。[方法]采用高效液相色谱法检测茶多酚种类和含量。[结果]市售绿茶均含有没食子儿茶素(GC)、表没食子儿茶素(EGC)和表没食子儿茶素没食子酸酯(EGCG)、表儿茶素(EC)和表儿茶素没食子酸酯(ECG)等茶多酚,以及没食子酸(GA)和咖啡因(CAF),EGCG为4种绿茶有效成分中的主要物质。半发酵茶铁观音7种有效成分全部检出,EGCG含量最高为16.610 mg/g。发酵茶红茶中茶多酚(儿茶素)部分被降解,GC、EGC、EGCG含量低,咖啡因含量高为17.304 mg/g;滇红茶中EGCG和ECG含量最高,分别为4.588和3.559 mg/g;普洱茶主要有效成分为没食子酸和咖啡因,几乎测不出其他5种茶多酚。[结论]茶叶不同发酵工艺使茶多酚不同程度被降解。 相似文献
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高效液相法测定普洱茶焙烤制品中儿茶素及咖啡碱含量的研究 总被引:1,自引:1,他引:0
为准确测定普洱茶经焙烤后有效物质儿茶素及咖啡碱的保留率,建立了高效液相法,采用70%甲醇提取液提取茶焙烤制品中的儿茶素,并使用C18反相色谱柱,以乙酸乙腈-乙酸水为流动相进行梯度洗脱,流速为1 mL/min;在波长为270 nm下经紫外分光法检测,结果表明:普洱茶粉的有效成分在焙烤过程中的保留率高,其中总儿茶素的平均保留率达90.55%,咖啡碱的平均保留率高达99.46%,因此该检测方法具有简便、准确、分离效果好的优点,适用于检测茶焙烤食品中儿茶素的含量。 相似文献
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AIM: The cancer biology has showed that overexpression of oncogenes is responsible for the progression of human malignancies,antisense technology can block a certain gene expression.Caffeine has enhancement effect on chemotherapy of osteosarcoma cells to cisplatin,we constructed the recombinant adenovirus (Ad-Asc-myc) encoding antisense c-myc fragment and investigated its effect on the in vitro sensitivity of osteosarcoma MG-63 cells to cisplatin.METHODS: The recombinant adenovirus (Ad-Asc-myc) encoding antisense c-myc fragment was constructed by cloning c-myc cDNA of about 750 base pairs in a reverse direction into adenovirus vector.Ad-Asc-myc and caffeine was used respectively or together to co-operate with cisplatin to treat the osteosarcoma MG-63 cells in vitro,and Western blotting,MTT,flow cytometry (FCM),electron microscope were used to evaluate expression of c-Myc protein,tumor cell proliferation in vitro,apoptosis and cell cycle analysis.RESULTS: Ad-Asc-myc was obtained with the titer of 2×1012 pfu/L.Ad-Asc-myc down-regulated the expression of c-Myc protein,Ad-Asc-myc or caffeine enhanced the effects of 2.0,5.0 mg/L cisplatin on MG-63 cells.Moreover,Ad-Asc-myc combined with caffeine significantly enhanced this effects,not only on cisplatin-induced apoptosis,but also on tumor cells proliferation in vitro.The expression of bcl-2 was downregulated,bax were upregulated,while there was no change in the expression of E2F-1.FCM analysis showed that cisplatin treatment induced a block in S phase,and caffeine reversed this block and speeded up the progression of cells out of the S phase.Ad-Asc-myc induced obvious G2/M phase arrest in transfected cells.CONCLUSION: Ad-Asc-myc combined with caffeine may enhance apoptosis-induced and chemotherapy effects of osteosarcoma MG-63 cells to cisplatin. 相似文献
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超临界CO_2提取茶叶中咖啡碱 总被引:8,自引:0,他引:8
用超临界萃取技术分离提取茶叶中的咖啡碱,再用CH2Cl2萃取分离,得到纯度为95.16%的咖啡碱,萃取率和得率分别为16.85%、0.55%。试验结果还表明,在一定条件下,利用超临界萃取技术能够有效地分离茶多酚和咖啡碱。 相似文献
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Green tea is a beverage that is produced by hot-water extraction of the leaves of tea (Camellia sinensis L.). As the amount of green tea consumption has increased, the importance of using the residue has grown. To address this problem, chemical compositions of two pyrolyzates obtained with an electric kiln, L and G, which were obtained from the tea leaf product and its hot-water extraction residue, respectively, were examined. Both pyrolyzates were alkaline, in contrast to the acidic pHs that are typical of pyrolyzates from wood materials. The major constituents were nitrogen-containing compounds, which accounted for up to about 70% (based on gas chromatography-mass spectrometry peak area). Caffeine was the main compound in both samples, although it might not be a pyrolysis product but actually sublimates from the samples and then condenses back into the pyrolyzates. Other nitrogen-containing compounds were formed mainly from proteins and amino acids. Acids and phenols, which are typical components in pyrolyzates obtained from wood materials and contribute to acidic pH, were rare in both samples. Other neutral compounds are known as compounds in pyrolyzates from wood materials. The pyrolyzates obtained in this experiment were novel and may have new uses.Contents of this report was presented in the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, 2002 相似文献
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Reto M Figueira ME Filipe HM Almeida CM 《Plant foods for human nutrition (Dordrecht, Netherlands)》2007,62(4):139-144
To evaluate the potential benefits and risks associated with tea consumption it is important to identify the constituents
of this beverage. Levels of some minerals, caffeine and catechins in green tea samples commercialized in Portugal were evaluated.
Potassium is the metal present in larger amount (92–151 mg/l). The content of sodium, calcium, fluoride, aluminium, manganese
and iron were 35–69, 1.9–3.5, 0.80–2.0, 1.0–2.2, 0.52–1.9, 0.020–0.128 mg/l, respectively. Chromium and selenium were not
detected. The resulting data showed considerable variability in catechins content. The levels of epigallocatechin gallate
(EGCG) ranged from 117 to 442 mg/l, epicatechin 3-gallate (EGC) from 203 to 471 mg/l, epigallocatechin (ECG) from 16.9 to
150 mg/l, epicatechin (EC) from 25 to 81 mg/l and catechin (C) from 9.03 to 115 mg/l. Caffeine contents in the green tea infusions
studied were between 141–338 mg/l. Green tea infusions provide significant amounts of catechins and could be an important
source of some minerals. 相似文献
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