首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   24篇
  免费   0篇
化学   23篇
物理学   1篇
  2023年   2篇
  2022年   3篇
  2021年   1篇
  2020年   2篇
  2018年   1篇
  2017年   1篇
  2016年   3篇
  2010年   2篇
  2009年   3篇
  2007年   2篇
  2005年   2篇
  2004年   1篇
  2003年   1篇
排序方式: 共有24条查询结果,搜索用时 15 毫秒
11.
Anion-exchange resin (AER) and choline chloride-based deep eutectic solvent-modified anion-exchange resin (DES-AER) were prepared, and their performance properties were assessed by Fourier transform infrared spectrometer (FTIR), field emission scanning electron microscopy (FE-SEM), and adsorption experiments. In addition, the separation characteristics on the solid-phase extraction (SPE) cartridges packed with octadecyl silica (ODS), AER, and DES-AER for rapid extraction of cleistanthol from Phyllanthus flexuosus extracts have been evaluated, with recoveries of the materials tested at 72.14, 68.21, and 82.11%, respectively. All results demonstrated that DES-AER not only offered higher adsorption capacity for cleistanthol but also exhibited better extraction efficiency of cleistanthol than those of ODS and AER. In this work, it is the first application of DES in the modification of AER, and the proposed DES-AER showed significant affinity and selectivity toward cleistanthol, which could have potential application for natural product extraction.  相似文献   
12.
The separation of polar compounds is challenging work due to poor retention and insufficient selectivity. In the present study, an efficient strategy for large-scale preparation of five polar polyphenols including three isomers from Phyllanthus emblica Linn has been established by preparative high-speed counter-current chromatography. Macroporous resin column chromatography was used for the enrichment of the polar polyphenols. However, sugar and other ultra-polar impurities were co-washed out with the targets. Liquid-liquid extraction with ethyl acetate/water (1/1, v/v) solvent system was developed to remove the ultra-polar impurities with a clearance rate of 95%. Finally, the targets were introduced to preparative high-speed counter-current chromatography for separation using ethyl acetate/n-butanol/acetic acid/water (2/7/1/10, v/v/v/v) solvent system. As a result, 191 mg of Mucic acid 1,4-lactone 5-O-gallate, 370 mg of β-Glucogallin, 301 mg of Gallic acid, 195 mg of Mucic acid 1,4-lactone 3-O-gallate and 176 mg of Mucic acid 1,4-lactone 2-O-gallate with purity higher than 98% were obtained from 1.5 g of sample. Mucic acid 1,4-lactone 3-O-gallate, Mucic acid 1,4-lactone 3-O-gallate, and Mucic acid 1,4-lactone 2-O-gallate are isomers. The results showed that high-speed counter-current chromatography could be well developed for the separation of polar compounds from natural products.  相似文献   
13.
A new purine derivative, 3‐(3‐methylbut‐2‐en‐1‐yl)isoguanine ( 1 ), and a new cleistanthane‐type diterpenoid glucoside, 19‐hydroxyspruceanol 19‐Oβ‐D ‐glucopyranoside ( 2 ), together with eight known compounds were isolated from the whole plant of Phyllanthus reticulatus. The structures were elucidated by chemical and spectroscopic methods.  相似文献   
14.
The current study was conducted to exemplify the effect of debelalactone on tissue protection, chronic hepatic inflammation, hepatic protection and oxidative stress induced by diethyl nitrosamine in Wistar rats. Therefore, DEN (200 mg/kg) was used for the induction the hepatocellular carcinoma (HCC) and the level of serum alpha fetoprotein was used for the estimation and confirmation of HCC. The study illustrated that debelalactone (DL) significantly downregulated the hepatic, non-hepatic parameters such as aspartate aminotransferase, alanine aminotransferase, alpha fetoprotein, NO levels, total protein, albumin, blood urea nitrogen, total bilirubin, and direct bilirubin in dose dependent manner, as well as noticeably improving the body weight, of treated animals. The macroscopically observation of DEN-induced rat liver showed the formation of informalities in liver tissue, which was reduced with treatment of DL at dose dependent manner. However, antioxidant markers and inflammatory mediators such as lipid peroxidation, catalase, superoxide dismutase, glutathione peroxidase and transferase, TNF-α, IL-1β, IL-6, and NF-kB restored up to the normal level by DL. The histopathology studies showed that the treated group of animals returned to a normal status. Collectively, it can be concluded that debelalactone mediated chemoprevention in the DEN-induced rats via an increase in the activities of endogenous enzymes and/or inhibition the precancerous cells.  相似文献   
15.
Phyllanthus species are extensively used in traditional medicines for the treatment of hepatic diseases due to their bioactive hypophyllanthin and phyllanthin. This work describes the development and validation of an ultra high performance liquid chromatography with tandem mass spectrometry method in polarity switching multiple reaction monitoring mode for the simultaneous detection and quantitation of 23 compounds using ultra‐performance liquid chromatography coupled with electrospray‐hybrid triple quadrupole‐linear ion trap mass spectrometer. The validated parameters showed good linearity (R 2 ≥ 0.996), limit of detection (0.05–1.62 ng/mL), limit of quantitation (0.15–4.95 ng/mL), precisions (intra‐day: RSD ≤ 2.11%), (inter‐day: RSD ≤ 2.91%), stability (RSD ≤ 2.56%) and overall recovery (98.22–104.48%; RSD ≤ 2.93%). The validated method was successfully applied in ethanolic extracts of P. amarus, P. niruri , P. emblica , P. fraternus , fractions of P. amarus and their herbal formulations for quantitation. The maximum content of hypophyllanthin (29.40 mg/g) and phyllanthin (56.60 mg/g) was detected in ethyl acetate fraction of P. amarus . The total content of 23 compounds was abundant in the ethanolic extract of P. emblica fruit. Principal component analysis was used to differentiate the selected Phyllanthus species and their herbal formulations. The results indicated that the present method could be used for quality control of Phyllanthus species and its herbal formulations.  相似文献   
16.
During the process of exploring bioactive lead compounds from Phyllanthus species, two new glycosides including an arylnaphthalene lignan, diphyllin 4-O-α-l-arabinopyranosyl-(1 → 3)-α-l-arabinopyranoside (1), and a phenolic compound, 3,4,5-trimethoxybenzyl alcohol 7-O-α-l-arabinofuranosyl-(1 → 6)-β-d-glucopyranoside (2), were isolated from the methanol extract of the whole plants of Phyllanthus glaucus Wall. ex Müll. Arg. In addition, 31 known compounds, including 19 lignan derivatives (321), four phenylpropanoids (2225), seven simple phenolics (2632) and one monoterpenoid (33) were obtained. Their structures were determined on the basis of the HR-ESI-MS, 1D and 2D NMR spectroscopic analysis, and pre-column derivative/chiral HPLC analysis in case of 1 for the absolute configurations. All these compounds were obtained from P. glaucus for the first time. Moreover, the known lignan glycoside, phyllanthusmin C (5) showed in vitro cytotoxicities against HL-60, MCF-7 and SW480 cells with IC50 values of 9.2 ± 0.2, 19.2 ± 1.7 and 20.5 ± 0.9, respectively.  相似文献   
17.
In the present work, an effort has been made to utilize Phyllanthus emblica (PE) fruit stone as a potential biomaterial for the sustainable remediation of noxious heavy metals viz. Pb(II) and Cd(II) from the aqueous solution using adsorption methodology. Further, to elucidate the adsorption potential of Phyllanthus emblica fruit stone (PEFS), effective parameters, such as contact time, initial metal concentration, temperature, etc., were investigated and optimized using a simple batch adsorption method. It was observed that 80% removal for both the heavy metal ions was carried out within 60 min of contact time at an optimized pH 6. Moreover, the thermodynamic parameters results indicated that the adsorption process in the present study was endothermic, spontaneous, and feasible in nature. The positive value of entropy further reflects the high adsorbent–adsorbate interaction. Thus, based on the findings obtained, it can be concluded that the biosorbent may be considered a potential material for the remediation of these noxious impurities and can further be applied or extrapolated to other impurities.  相似文献   
18.
建立了叶下珠药材中黄酮的毛细管电泳指纹图谱。以硼砂和十二烷基磺酸钠(pH9.0)为背景电解质溶液,运行电压15kV,紫外检测波长245nm,流体静压力进样15s(高度12cm),对不同产地叶下珠药材进样检测。按电泳峰共有率fi≥70%为依据,确定10个不同产地叶下珠药材中黄酮的毛细管电泳指纹峰为8个,各产地叶下珠的毛细管电泳指纹图谱与标准毛细管电泳指纹图谱的相似度较好。在制备供试液后不同时间进样测定,各指纹峰的相对迁移时间的相对标准偏差小于5%,相对峰面积的相对标准偏差在3.0%~7.8%之间,结果表明样品在48h内稳定。  相似文献   
19.
In this paper, the quality of Phyllanthus emblica was evaluated by establishing a comprehensive taste index and odor component analysis method, and the formation mechanism of quality difference was revealed by mass spectrometry imaging and metabolomics. Studies have found that the representative substances of bitterness and astringency in cultivated PE, such as amlaic acid, kaempferol, quercetin and their derivatives, have higher content. Compared with wild PE, cultivated PE has a very lower 2-Isobutyl-3-methoxypyrazine content, a kind of odor molecule that destroys the fruits flavor. Biological activity studies showed that the biological activity of wild PE was stronger than cultivated PE. Mass spectrometry imaging revealed significant differences in the distribution of multiple components between the two types of PE. Metabonomic studies show that their quality differences may be related to the difference of flavonoids and flavonol biosynthesis in PE.  相似文献   
20.
高效液相色谱法测定余甘子中单宁酸的含量   总被引:1,自引:0,他引:1  
建立了高效液相色谱法测定余甘子中单宁酸含量的方法,采用Hypersil ODS(125×4.0 mm,5μm)色谱柱;检测波长275nm;流动相为80%甲醇和20%水;流速为0.5mL·min-1.可在3min内完成一次样品分析.所测单宁酸在120-240 ng/mL的范围内有良好的线性关系.相关系数达99.996%以上,加标回收率在99.7%-107.5%之间.本法快速,方便,精确可靠.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号