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51.
Rubber composites with very high moduli at low elongation, high elongation at break and high ultimate breaking strength have been developed. The matrix was acrylonitrile butadiene rubber (NBR) and the hybrid (fibrous and particulate) reinforcements were short, fine pineapple leaf fiber (PALF) and carbon black. The amount of PALF was fixed at 10 parts (by weight) per hundred of rubber (phr) while that of carbon black was varied from 0 to 30 phr. Uniaxial NBR composites were prepared. Tensile strength, elongation at break, modulus and tear strength of the hybrid composites were characterized in both longitudinal (parallel to the fiber axis) and transverse (perpendicular to the fiber axis) directions. The addition of carbon black causes the slope of the early part of the stress–strain curve to increase and also extends breaking to greater strains. At carbon black contents of 20 phr and above, the stress–strain relation displays an upturn at high elongations, providing greater ultimate strength. Comparison with the usual carbon black filled rubber shows that the composite behavior at low strains is determined by the PALF, and at high strains by the carbon black. This high performance PALF-carbon black reinforced NBR shows great promise for engineering applications. 相似文献
52.
An ionic liquid aqueous solvent‐based microwave‐assisted hydrolysis (ILAS‐MAH) approach was proposed for the rapid extraction and accurate determination of myricetin and quercetin from Myrica rubra (M. rubra) leaves for the first time. The effects of the ionic liquid class and concentration, liquid–solid ratio, hydrolysis temperature and time were investigated to obtain the optimal ILAS‐MAH conditions. The optimized conditions were 2.0 mol/L [bmin][HSO4] or 2.5 mol/L acidified [bmin]Br solution, liquid–solid ratio 30:1 (mL : g), hydrolysis temperature 70°C and hydrolysis time 10 min. Under these conditions, the recoveries of myricetin and quercetin were in the range of 86.3–107.3% with relative standard deviation lower than 5.8%. Compared with conventional heating hydrolysis and regular MAH, the proposed approach reduced hydrolysis time and improved yields. The mechanism of ILAS‐MAH was also investigated. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
53.
54.
Ishida N 《Journal of chromatography. A》2011,1218(34):5810-5818
An improved separation method for chlorophyll metabolites in Oriental tobacco leaf was developed. While Oriental leaf still gives the green color even after the curing process, little attention has been paid to the detailed composition of the remaining green pigments. This study aimed to identify the green pigments using non aqueous reversed phase chromatography (NARPC). To this end, liquid chromatograph (LC) equipped with a photo diode array detector (DAD) and an atmospheric pressure chemical ionization/mass spectrometer (APCI/MSD) was selected, because it is useful for detecting low polar non-volatile compounds giving green color such as pheophytin a. Identification was based on the wavelength spectrum, mass spectrum and retention time, comparing the analytes in Oriental leaf with the commercially available and synthesized components. Consequently, several chlorophyll metabolites such as hydroxypheophytin a, solanesyl pheophorbide a and solanesyl hydroxypheophorbide a were newly identified, in addition to typical green pigments such as chlorophyll a and pheophytin a. Chlorophyll metabolites bound to solanesol were considered the tobacco specific components. NARPC expanded the number of detectable low polar chlorophyll metabolites in Oriental tobacco leaf. 相似文献
55.
Attilio Anzano Bruna de Falco Mohammad Ammar Annarita Ricciardelli Laura Grauso Mohammed Sabbah Rosanna Capparelli Virginia Lanzotti 《Molecules (Basel, Switzerland)》2022,27(24)
Moringa oleifera is a traditional food crop widespread in Asiatic, African, and South American continents. The plant, able to grow in harsh conditions, shows a high nutritional value and medicinal potential evidencing cardioprotective, anti-inflammatory, antioxidant, and antimicrobial properties. The purpose of this study was the phytochemical analysis of M. oleifera and the identification of the antimicrobial compounds by combining a chemical approach with in vitro tests. The metabolite profile of M. oleifera polar and apolar extracts of leaves and seeds were investigated by using Nuclear Magnetic Resonance spectroscopy and Gas Chromatography-Mass Spectrometry. The antimicrobial activity of all of the obtained extract was evaluated against four bacterial pathogens (Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Salmonella enterica). The chemical analysis provided a wide set of metabolites that were identified and quantified. Moreover, apolar extracts from seeds showed a significant concentration-dependent antimicrobial activity against S. aureus and S. epidermidis, (4 mg/mL reduced the viability up to 50%) that was associated to the content of specific fatty acids. Our results remarked the advantages of an integrated approach for the identification of plant metabolites and its use in association with biological tests to recognize the compounds responsible for bioactivity without compounds purification. 相似文献
56.
Harvesting seasons are crucial for the physicochemical qualities of large-leaf-variety black tea. To investigate the effect of harvesting seasons on physicochemical qualities, the color and sensory characteristics of black tea produced from “Yinghong 9” (Yh) and its mutant “Huangyu” (Hy) leaves were analyzed. The results demonstrated that Hy had better chemical qualities and sensory characteristics, on average, such as a higher content of tea polyphenols, free amino acids, caffeine, galloylated catechins (GaCs) and non-galloylated catechins (NGaCs), while the hue of the tea brew (ΔE*ab and Δb*) increased, which meant that the tea brew was yellower and redder. Moreover, the data showed that the physicochemical qualities of SpHy (Hy processed in spring) were superior to those of SuHy (Hy processed in summer) and AuHy (Hy processed in autumn), and 92.6% of the total variance in PCA score plots effectively explained the separation of the physicochemical qualities of Yh and Hy processed in different harvesting seasons. In summary, Hy processed in spring was superior in its physicochemical qualities. The current results will provide scientific guidance for the production of high-quality large-leaf-variety black tea in South China. 相似文献
57.
Sonu Kumar Rajveer Singh Debrupa Dutta Shivani Chandel Arka Bhattacharya Velayutham Ravichandiran Soumi Sukla 《Molecules (Basel, Switzerland)》2022,27(23)
Natural products are being targeted as alternative anticancer agents due to their non-toxic and safe nature. The present study was conducted to explore the in vitro anticancer potential of Justicia adhatoda (J. adhatoda) leaf extract. The methanolic leaf extract was prepared, and the phytochemicals and antioxidant potential were determined by LCMS analysis and DPPH radical scavenging assay, respectively. A docking study performed with five major alkaloidal phytoconstituents showed that they had a good binding affinity towards the active site of NF-κB. Cell viability assay was carried out in five different cell lines, and the extract exhibited the highest cytotoxicity in MCF-7, a breast cancer cell line. Extract-treated cells showed a significant increase in nitric oxide and reactive oxygen species production. Cell cycle analysis showed an arrest in cell growth at the Sub-G0 phase. The extract successfully inhibited cell migration and colony formation and altered mitochondrial membrane potential. The activities of superoxide dismutase and glutathione were also found to decrease in a dose-dependent manner. The percentage of apoptotic cells was found to increase in a dose-dependent manner in MCF-7 cells. The expressions of caspase-3, Bax, and cleaved-PARP were increased in extract-treated cells. An increase in the expression of NF-κB was found in the cytoplasm in extract-treated cells. J. adhatoda leaf extract showed a potential anticancer effect in MCF-7 cells. 相似文献
58.
Sandrine Da Ressurreio Snia Pedreiro Maria Teresa Batista Artur Figueirinha 《Molecules (Basel, Switzerland)》2022,27(21)
Dyslipidemias are one of the risk factors for cardiovascular diseases, the leading cause of death and hospitalization worldwide. One way to control cholesterol levels is to control the exogenous cholesterol intake in the body. Natural polyphenolic compounds, namely theaflavins from plant extracts such as black tea, showed the ability to inhibit the formation of the micellar structure, essential for the absorption of cholesterol in the intestine. There are several methodologies to determine this effect, many of which are expensive and time-consuming. Due to these facts, the main purposes of this work were to optimize an inexpensive colorimetric method to study, in vitro, the micellar solubility of cholesterol and applied it to plant extracts. In this work, Cymbopogon citratus leaf extracts, its phenolic fractions, and flavonoids were evaluated. The non-delipidified infusion (CcI) obtained a maximum percentage of micelle destruction of 59.22% for a concentration of 50 μg/mL and the delipidified infusion (CcdI) obtained a maximum percentage of micelle destruction of 58.01% for a concentration of 200 μg/mL. In the case of the fraction of phenolic acids (CcPAs), 23.85% of maximum micellar destruction was recorded for the concentration of 100 μg/mL, while for the fraction of flavonoids (CcF), the micellar destruction was 92.74% at 1 μg/mL, and for the tannin fraction (CcT) of 99.45% at 25 μg/mL. Luteolin presented a percentage of micelle destruction of 94.83% in the concentration of 1 ng/mL, followed by luteolin-7-O-glucoside with 93.71% and luteo-lin-6-C-glucoside with 91.26% at the concentrations of 25 ng/mL and 50 ng/mL, respectively. These results suggest the capability of polyphenols from Cymbopogon citratus to prevent the cholesterol absorption in the gut by micellar destruction, and its contribution for cholesterol-lowering activity. 相似文献
59.
Ummi Kalthum Azlan Ahmed Mediani Emelda Rosseleena Rohani Xiaohui Tong Rongchun Han Norazlan Mohmad Misnan Faidruz Azura Jam Hamidun Bunawan Murni Nazira Sarian Hamizah Shahirah Hamezah 《Molecules (Basel, Switzerland)》2022,27(18)
Moringa oleifera is an ancient remedy plant, known as the miraculous plant due to its many prominent uses and significant health benefits. It is a nutrient-rich plant, with exceptional bioactive compounds, such as polyphenols that possess several medicinal properties. Many significant studies have been carried out to evaluate the ethnomedicinal and pharmacological properties of M. oleifera in various applications. Therefore, this comprehensive review compiles and summarizes important findings from recent studies on the potential properties of different parts of M. oleifera. The pharmacological properties of M. oleifera have been studied for various potential biological properties, such as cardio-protective, anti-oxidative, antiviral, antibacterial, anti-diabetic and anti-carcinogenic effects. Therefore, the potential of this plant is even more anticipated. This review also highlights the safety and toxicity effects of M. oleifera treatment at various doses, including in vitro, in vivo and clinical trials from human studies. 相似文献
60.
用清除羟自由基法评价竹叶提取物抗氧化能力 总被引:6,自引:0,他引:6
进行了Fe2+与邻二氮菲生成红色配合物的吸收光谱,抗氧化剂TBHQ及竹叶提取物样品对清除羟自由基能力的研究。分光光度法测定抗氧化剂清除羟自由基能力的测定波长为509.1 nm。以IC50值(清除率为50%时,抗氧化剂的浓度值)作为评价抗氧化剂清除羟自由基能力的指标,测得合成抗氧化剂和效果最好竹叶提取物样品IC50值分别为0.040(TBHQ),0.378(M20),0.323(M40),0.334(M60),M20, M40, M60等竹叶提取物可以作为天然抗氧化剂进行开发。 相似文献