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排序方式: 共有816条查询结果,搜索用时 203 毫秒
1.
Sze-Jack Tan Chee-Keong Lee Chee-Yuen Gan Olusegun Abayomi Olalere 《Molecules (Basel, Switzerland)》2021,26(7)
In this study, the combination of parameters required for optimal extraction of anti-oxidative components from the Chinese lotus (CLR) and Malaysian lotus (MLR) roots were carefully investigated. Box–Behnken design was employed to optimize the pH (X1: 2–3), extraction time (X2: 0.5–1.5 h) and solvent-to-sample ratio (X3: 20–40 mL/g) to obtain a high flavonoid yield with high % DPPHsc free radical scavenging and Ferric-reducing power assay (FRAP). The analysis of variance clearly showed the significant contribution of quadratic model for all responses. The optimal conditions for both Chinese lotus (CLR) and Malaysian lotus (MLR) roots were obtained as: CLR: X1 = 2.5; X2 = 0.5 h; X3 = 40 mL/g; MLR: X1 = 2.4; X2 = 0.5 h; X3 = 40 mL/g. These optimum conditions gave (a) Total flavonoid content (TFC) of 0.599 mg PCE/g sample and 0.549 mg PCE/g sample, respectively; (b) % DPPHsc of 48.36% and 29.11%, respectively; (c) FRAP value of 2.07 mM FeSO4 and 1.89 mM FeSO4, respectively. A close agreement between predicted and experimental values was found. The result obtained succinctly revealed that the Chinese lotus exhibited higher antioxidant and total flavonoid content when compared with the Malaysia lotus root at optimum extraction condition. 相似文献
2.
3.
Umie F.M. Haziz Rosenani A. Haque Shun-Ze Zhan Hassan H. Abdallah Mohd R. Razali 《应用有机金属化学》2020,34(10):e5818
The synthesis and characterizations for a series of dinuclear gold (I)-di-NHC complexes, 1–8 through the trans-metalation method of their respective silver (I)-di-NHC complexes, i–viii are reported (where NHC = N-heterocyclic carbene). The successful complexation of a series of unusual non-symmetrical and symmetrical di-NHC ligands, 3,3'-(ethane-1,2-diyl)-1-alkylbenzimidazolium-1'-butylbenzimidazolium (with alkyl = methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, benzyl) with the gold (I) ions are suggested by elemental analysis, Fourier transform-infrared, 1H- and 13C-NMR data. The 13C-NMR spectra of 1–8 show a singlet sharp peak in the range of 190.00–192.00 ppm, indicating the presence of a carbene carbon that bonded to the gold (I) ion. From single crystal X-ray diffraction data, the structure of complex 6 with the formula of [di-NHC-Au (I)]2·2PF6 is obtained [where NHC = 3,3'-(ethane-1,2-diyl)-1-hexylbenzimidazolium-1'-butylbenzimidazolium]. The photophysical study in solid state of 6 displays an intense photoluminescence with a strong emission maxima, λem = 480 nm, upon excitation at 340 nm at room temperature. Interestingly, the emission maximum at 77 K shows a structural character with a strong peak at 410 nm, a medium at 433 nm and a weak at 387 nm, accompanied by a tail band to about 500 nm. 相似文献
4.
N. A. Hussein A. Shukri A. A. Tajuddin C. S. Chong 《Radiation Physics and Chemistry》2004,71(6):1077-1086
Osteoporosis is a bone condition that is caused mainly by the degradation of trabecular and cortical bone resulting in the decrease of bone strength and eventually leads to bone fracture. A low angle X-ray scattering (LAXS) system that uses mainly the coherent scattering process for the characterisation of materials was constructed to study such bone conditions. Several finger phantoms were fabricated to simulate bone of varying densities. The LAXS method was able to identify the changes in bone density quite well by comparing energy dispersive X-ray diffraction patterns as well as the angular patterns. Quantitative information can be extracted from such patterns that relate to bone loss. Signature patterns at low exposure times were produced in order to reduce the dose received with reasonable identification power but at slightly higher statistical errors compared with long exposure patterns. Use of other parameters to increase the sensitivity was attempted. 相似文献
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6.
《Physica A》2006,360(1):59-70
The influence of habitat destruction on a population of predators and prey is studied. We show, via Monte Carlo simulations of a lattice model, that with growing devastation the oscillations in the densities of both species, as well as cross-correlations between the two densities diminish. As should be expected, predators are more vulnerable and disappear before the prey. Devastation of the habitat is never beneficial and the percentage of coexisting (prey and predators) states decreases with destruction. Because of the high fragmentation of the environment in the case of large devastation, animals’ populations are separated into small sub-populations living in restricted areas. Such small populations become extinct more easily. We have also shown that in the case of large habitat devastation the density of the population of prey depends on its history. 相似文献
7.
X-射线晶体结构分析表明,在90℃的水热条件下,N-(8-喹啉基)吡啶-3-酰胺在Cd2+的存在下发生醇解。醇解产物为8-氨基喹啉(HL1)和吡啶-3-羧乙酯(HL2),它们与Cd(Ⅱ)配位形成四方锥型化合物。该配合物为单斜晶系,空间群P21/c,a=18.1089(1)?,b=8.9986(1)?,c=19.3070(2)?,β=113.085(1 相似文献
8.
A new crystal-engineering motif has been developed where a ditopic receptor 1 shows a novel syn-syn hydrogen-bonded polymeric supramolecular complex (Fig. 4b) (instead of a 1:1 dimeric syn-syn or polymeric syn-anti complex) giving rise to a hydrogen-bonded stair-like polymeric ribbon structure between the binding groups of the receptor pyridine amide and the carboxyl groups of the guest substrate. 相似文献
9.
Wen Ma Yu-Peng Tian Sheng-Yi Zhang Jie-Ying Wu Hoong-Kun Fun Suchada Chantrapromma 《Transition Metal Chemistry》2006,31(1):97-102
A new diferrocenyl-substituted macrocyclic ligand (H2L) and its complexes ML(M = CuII, NiII, ZnII, CdII) were prepared and characterized by IR, elemental analysis, absorption spectra and FAB mass spectra. The ferrocenyl-substituted
macrocyclic ligand was characterized by single crystal X-ray diffraction analysis. The superconjugative effect of the cyclopentadienyl
(CP) rings increase the activity of the hydrogen atoms in the tetra-azacyclotetradecane macrocyclic ligand. The imine nitrogen
atoms lose two protons and coordinate to the metal. The electrochemical properties of these compounds are discussed. 相似文献
10.
《Radiation Physics and Chemistry》2006,75(11):1519-1521
X-ray absorption near edge structure (XANES) spectra at the cooper L2,3-edge of small cooper nanoclusters has been studied. Theoretical interpretation of XANES spectra measured for small copper nanoclusters have been performed. Theoretical analysis is based on a self-consistent full multiple scattering theory of X-ray absorption as well as on non-muffin-tin finite difference method (FDM). This approach allows choosing the best model for local geometry of small cooper nanoclusters. 相似文献