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排序方式: 共有655条查询结果,搜索用时 453 毫秒
561.
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563.
Ezzouhra El Maaiden Sarah Bouzroud Boubker Nasser Khadija Moustaid Ayoub El Mouttaqi Mohamed Ibourki Hassan Boukcim Abdelaziz Hirich Lamfeddal Kouisni Youssef El Kharrassi 《Molecules (Basel, Switzerland)》2022,27(7)
This study aimed to compare the influence of extraction methods on the pharmaceutical and cosmetic properties of medicinal and aromatic plants (MAPs). For this purpose, the dried plant materials were extracted using advanced (microwave (MAE), ultrasonic (UAE), and homogenizer (HAE) assisted extractions) and conventional techniques (maceration, percolation, decoction, infusion, and Soxhlet). The tyrosinase, elastase, α-amylase, butyryl, and acetylcholinesterase inhibition were tested by using L-3,4 dihydroxy-phenylalanine, N-Succinyl-Ala-Ala-p-nitroanilide, butyryl, and acetylcholine as respective substrates. Antioxidant activities were studied by ABTS, DPPH, and FRAP. In terms of extraction yield, advanced extraction techniques showed the highest values (MAE > UAE > HAE). Chemical profiles were dependent on the phenolic compounds tested, whereas the antioxidant activities were always higher, mainly in infusion and decoction as a conventional technique. In relation to the pharmaceutical and cosmetic properties, the highest inhibitory activities against α-amylase and acetylcholinesterase were observed for Soxhlet and macerated extracts, whereas the highest activity against tyrosinase was obtained with MAE > maceration > Soxhlet. Elastase and butyrylcholinesterase inhibitory activities were in the order of Soxhlet > maceration > percolation, with no activities recorded for the other tested methods. In conclusion, advanced methods afford an extract with high yield, while conventional methods might be an adequate approach for minimal changes in the biological properties of the extract. 相似文献
564.
Narendar Dudhipala Swetha Ettireddy Ahmed Adel Ali Youssef Goverdhan Puchchakayala 《Molecules (Basel, Switzerland)》2021,26(24)
Irbesartan (IR) is an angiotensin II receptor antagonist drug with antihypertensive activity. IR bioavailability is limited due to poor solubility and first-pass metabolism. The current investigation aimed to design, develop, and characterize the cyclodextrin(s) (CD) complexed IR (IR-CD) loaded solid lipid nanoparticles (IR-CD-SLNs) for enhanced solubility, sustained release behavior, and subsequently improved bioavailability through oral administration. Based on phase solubility studies, solid complexes were prepared by the coacervation followed by lyophilization method and characterized for drug content, inclusion efficiency, solubility, and in vitro dissolution. IR-CD inclusion complexes demonstrated enhancement of solubility and dissolution rate of IR. However, the dissolution efficiency was significantly increased with hydroxypropyl-βCD (HP-βCD) inclusion complex than beta-CD (βCD). SLNs were obtained by hot homogenization coupled with the ultrasonication method with IR/HP-βCD inclusion complex loaded into Dynasan 112 and glycerol monostearate (GMS). SLNs were evaluated for physicochemical characteristics, in vitro release, differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD), and physical stability at room temperature for two months. The optimized SLNs formulation showed particle size, polydispersity index, zeta potential, assay, and entrapment efficiency of 257.6 ± 5.1 nm, 0.21 ± 0.03, −30.5 ± 4.1 mV, 99.8 ± 2.5, and 93.7 ± 2.5%, respectively. IR-CD-SLN and IR-SLN dispersions showed sustained release of IR compared to the IR-CD inclusion complexes. DSC results complimented PXRD results by the absence of IR endothermic peak. Optimized IR-CD complex, IR-SLN, and IR-CD-SLN formulations were stable for two months at room temperature. Thus, the current IR oral formulation may exhibit improved oral bioavailability and prolonged antihypertensive activity, which may improve therapeutic outcomes in the treatment of hypertension and heart failure. 相似文献
565.
S. Youssef 《The European Physical Journal C - Particles and Fields》2000,15(1-4):202-204
Monte Carlo techniques are often the only practical way to evaluate difficult integrals or to sample random variables governed
by complicated probability density functions. Here we describe an assortment of methods for sampling some commonly occurring
probability density functions. 相似文献
566.
Stephen E. Bechtel Nivine T. Youssef M. Gregory Forest Hong Zhou Kurt W. Koelling 《Rheologica Acta》2001,40(4):373-383
A model for oscillating free surface jet flow of a fluid from an elliptical orifice, together with experimental measurements,
can be exploited to characterize the elongational viscosity of non-Newtonian inelastic fluids. The oscillating jet flow is
predominantly elongational, with a small strain that oscillates rapidly between large and zero strain rates. We find that
to reproduce the experimentally observed steady oscillating jet flow in model simulations, the assumed form of the non-Newtonian
viscosity as a function of strain rate must have zero gradient, i.e., be Newtonian, at zero strain rate (a behavior exhibited,
in general, by real inelastic fluids). We demonstrate that the Cross, Carreau, Prandtl-Eyring, and Powell-Eyring forms, although
they have finite viscosity at zero strain rate, have either nonzero or even unbounded gradient at zero, and hence are unable
to model oscillating jet behavior. We propose a new non-Newtonian viscous form which has all of the desirable features of
existing forms (high and low strain rate plateaus, with adjustable location and steepness of the transition) and the additional
feature of Newtonian behavior at low strain rates.
Received: 7 February 2000 Accepted: 31 October 2000 相似文献
567.
带球形空腔的广义热弹性无限大材料的弹性模量和传热系数与材料参考温度的相关性 总被引:2,自引:1,他引:1
利用具某一松弛时间的广义热弹性方程求解了带球形空腔的无限大材料问题.该材料的弹性模量和传热系数是可变的.空腔的内表面没有力作用,但有热冲击作用.利用Laplace变换求得直接逼近解.数值求解了Laplace逆变换.给出了温度、位移和应力的分布图. 相似文献
568.
A new acylated avicularin, namely avicularin 2'-(4'-O-n-pentanoyl)-gallate (1) along with 12 metabolites have been isolated from the ethyl acetate extract of the aerial parts of Jussiaea repens L. (Onagraceae). Their structures were established as trifolin 2'-O-gallate (2), quercetrin (3), guaijaverin (4), reynoutrin (5), juglanin (6), avicularin (7), hyperin (8), trifolin (9), hyperin 2'-O-gallate (10), rutin (11), kaempferol (12) and quercetin (13) on the basis of their chromatographic properties, chemical and spectroscopic evidences. The investigated ethyl acetate extract was found to be non-toxic (LD(50) up to the maximum soluble dose 4 g kg(-1) body wt.) and had significant antioxidant, hepatoprotective, anti-inflammatory and antidiabetic activities. Also some of the isolated flavonoids showed cytotoxic activity against Ehrlich ascitis carcinoma cells. 相似文献
569.
570.
Rafik W. Bassily Rimon H Youssef Ramadan I. El-Sokkary Mina A Nashed 《Journal of carbohydrate chemistry》2013,32(6):653-663
ABSTRACT The 13C NMR spectra of a range of di-O-isopropylidene acetals of α,α-trehalose and its analogues 1, 2, 4-7 have been studied Attention has been focussed on the chemical shifts of the acetal carbon and methyl groups of the acetals. These parameters are characteristic of ring-size (1,3-dioxolane and 1,3-dioxane). Di-n-butylstannylene and cyclic orthoester intermediates 9 and 12 of 2,6-di-O-benzoyl-α-D-galactopyranosyl 2,6-di-O-benzoyl-α-D-galactopyranoside (8) were used to synthesize the partially protected trehalose analogue having chain extension at positions 4,4′ and 3,3′ (10 and 13) respectively. Acetonation of the synthetic trehalose type disaccharide yielded mainly 3,4:3′,4′-di-O-isopropylidene derivative 4. The benzoylation of 4 followed by acid hydrolysis gave 8 in 85% yield, which was the key intermediate for the synthesis of 10 and 13 相似文献