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61.
Hammad Ullah Yaseen Hussain Cristina Santarcangelo Alessandra Baldi Alessandro Di Minno Haroon Khan Jianbo Xiao Maria Daglia 《Molecules (Basel, Switzerland)》2022,27(6)
Food spoilage makes foods undesirable and unacceptable for human use. The preservation of food is essential for human survival, and different techniques were initially used to limit the growth of spoiling microbes, e.g., drying, heating, salting, or fermentation. Water activity, temperature, redox potential, preservatives, and competitive microorganisms are the most important approaches used in the preservation of food products. Preservative agents are generally classified into antimicrobial, antioxidant, and anti-browning agents. On the other hand, artificial preservatives (sorbate, sulfite, or nitrite) may cause serious health hazards such as hypersensitivity, asthma, neurological damage, hyperactivity, and cancer. Thus, consumers prefer natural food preservatives to synthetic ones, as they are considered safer. Polyphenols have potential uses as biopreservatives in the food industry, because their antimicrobial and antioxidant activities can increase the storage life of food products. The antioxidant capacity of polyphenols is mainly due to the inhibition of free radical formation. Moreover, the antimicrobial activity of plants and herbs is mainly attributed to the presence of phenolic compounds. Thus, incorporation of botanical extracts rich in polyphenols in perishable foods can be considered since no pure polyphenolic compounds are authorized as food preservatives. However, individual polyphenols can be screened in this regard. In conclusion, this review highlights the use of phenolic compounds or botanical extracts rich in polyphenols as preservative agents with special reference to meat and dairy products. 相似文献
62.
Rasheed Ahmad Khera Munawar Hussain Nguyen Thai Hung Nadi Eleya Holger Feist Alexander Villinger Peter Langer 《Helvetica chimica acta》2012,95(3):469-482
Suzuki? Miyaura reactions of 2,3‐dibromo‐1H‐inden‐1‐one afforded a wide range of arylated 1H‐inden‐1‐ones. Sonogashira cross‐coupling reactions gave alkynylated indenones. The reactions proceeded with very good regioselectivity in the less sterically hindered and more electron‐deficient position 3. 相似文献
63.
High bit-rate (>10 Gb/s) signals are composed of very short pulses and propagation of such pulses through a semiconductor
optical amplifier (SOA) requires consideration of intraband phenomena. Due to the intraband effects, the propagating pulse
sees a fast recovering nonlinear gain which introduces less distortion in the pulse shape and spectrum of the output pulse
but introduces a positive chirping at the trailing edge of the pulse. 相似文献
64.
M. Sakhawat Hussain 《Journal of chemical crystallography》1986,16(1):91-99
The crystal and molecular structures of chloro(triphenylphosphineselenide)gold(I), [(C6H5)3PSe]AuCl, have been determined from three-dimensional X-ray intensity data collected on a CAD4 diffractometer. The compound crystallizes in the triclinic space groupPl witha=9.322(3),b=10.639(5),c=9.252(3) Å, =104.74(4), =99.52(3), =76.97(3)°, andZ=2. Atomic parameters were refined by full-matrix least-squares to anR value of 5.7% for 2591 observed reflections. This is one of the few known examples of linear gold(I) complexes having an Au-Se linkage. The Se-Au-Cl angle is 178.6(1)°, and the Au-Se and Au-Cl distances are 2.371(2) and 2.277(6) Å, respectively. As expected, the Au-Se bond length is 0.10–0.18 Å longer than the Au-S bond length observed in similar two-coordinate linear gold(I) complexes. 相似文献
65.
(+)-Parviflorine (), found in Lam. (Fumariaceae), is the first known glycosidic spirobenzylisoquinoline alkaloid. Its acid hydrolysis yields (+)-parfumine () and D-glucose. Klyne's rule indicates that is a β-D-glucoside. The absolute configuration shown in expressions is predominant among spirobenzylisoquinolines. A generalization has been drawn between plant source and the oxygenation pattern of ring C for the spirobenzylisoquinoline alkaloids. 相似文献
66.
Ahmad VU Hussain J Hussain H Farooq U Farmanullah Lodhi MA Choudhary MI 《Natural product research》2005,19(3):267-274
Two new myrsinol-type diterpene polyesters 3,5,13,17-tetra-O-acetyl-7-O-benzoyl-15-hydroxymyrsinol (1) and 3,5,13,17-tetra-O-acetyl-7-O-butanoyl-13-hydroxymyrsinol (2), with a tricyclic carbon skeleton have been isolated from Euphorbia decipiens Boiss. & Buhse. The structure elucidation of the isolated compounds was based primarily on HREIMS, EIMS, IR, UV, ID-, and 2D-NMR analyses, including COSY, HMQC, HMBC, and NOESY correlations. Compounds 1 and 2 also showed activity against urease enzyme. 相似文献
67.
The effect of simultaneous Sr substitution at the Ba and Y sites has been studied in the Sr0.75Y0.75Ba1.5Cu3O7–dsystem. Attempts to replace 25% Y and 25% Ba have been successful and superconductivity was observed above 78 K for Sr0.75Y0.75Ba1.5Cu3O7–d compound with high oxygen content, i.e., O6.76, and having orthorhombic crystal symmetry. The compound was treated in argon gas at 800°C to reduce the oxygen content and to induce some structural changes. The Sr0.75Y0.75Ba1.5Cu3O6.1 compound thus obtained has tetragonal symmetry and low oxygen content, O6.1. It has also shown superconductivity at 28 K. The paper presents a careful comparison of the structural and electrical properties and infrared absorbance spectra of the two compounds with the same metallic composition, Sr0.75Y0.75Ba1.5Cu3, but with different oxygen content and crystal symmetry. The study clearly establishes the occurrence of superconductivity in tetragonal Sr-substituted (both at Y and Ba sites in) YBCO. 相似文献
68.
Hussain HA Ansari AA Iftikhar K 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(4):873-884
The optical absorption and NMR studies of trivalent lanthanide chloride complexes with 2,2'-bipyridine (bpy) are presented and discussed. The NMR spectra of paramagnetic complexes exhibit lower as well as higher field shifts of bpy resonances that reflect change in geometry and reveals importance of the factor (3 cos2 theta - 1 ) in changing sign of the shift. The paramagnetic shifts recorded have been analyzed and the intramolecular shift ratios suggest that the paramagnetic shift is predominantly dipolar in origin. Electronic spectral studies of the Pr, Nd, Ho, Er and Dy complexes in different solvents (viz. methanol, pyridine, DMSO and DMF), which differ with respect to donor atoms, reveal that the chemical environment around the lanthanide ion has great impact on f-f transitions and any change in the environment results in modifications of the spectra. The oscillator strength for the hypersensitive and non-hypersensitive transitions have been determined and changes in the oscillator strength and band shape with respect to solvent type is rationalized in terms of ligand (solvent) structure and coordination properties. 相似文献
69.
70.
Brouet V Yang WL Zhou XJ Choi HJ Louie SG Cohen ML Goldoni A Parmigiani F Hussain Z Shen ZX 《Physical review letters》2004,93(19):197601
We observe, with angle-resolved photoemission, a dramatic change in the electronic structure of two C60 monolayers, deposited, respectively, on Ag (111) and (100) substrates, and similarly doped with potassium to half filling of the C60 lowest unoccupied molecular orbital. The Fermi surface symmetry, the bandwidth, and the curvature of the dispersion at Gamma point are different. Orientations of the C60 molecules on the two substrates are known to be the main structural difference between the two monolayers, and we present new band-structure calculations for some of these orientations. We conclude that orientations play a key role in the electronic structure of fullerides. 相似文献