Platelet-Activating Factor (PAF) Antagonistic Activity of a New Biflavonoid from <em>Garcinia nervosa</em> var. <em>pubescens</em> King

The methanol extract of the leaves of Garcinia nervosa var. pubescens King, which showed strong inhibitory effects on platelet-activating factor (PAF) receptor binding, was subjected to bioassay-guided isolation to obtain a new biflavonoid, II-3,I-5, II-5,II-7,I-4',II-4'-hexahydroxy-(I-3,II-8)-flavonylflavanonol together with two known flavonoids, 6-methyl-4'-methoxyflavone and acacetin. The structures of the compounds were elucidated by spectroscopic methods. The compounds were evaluated for their ability to inhibit PAF receptor binding to rabbit platelets using ³H-PAF as a ligand. The biflavonoid and acacetin showed strong inhibition with IC₅₀ values of 28.0 and 20.4 μM, respectively. The results suggest that these compounds could be responsible for the strong PAF antagonistic activity of the plant.     

MCM‐41‐SO3H as a nanoreactor for the one‐pot,solvent‐free synthesis of 1,8‐dioxo‐9‐aryl decahydroacridines

One‐pot four‐component synthesis of 1,8‐dioxo‐9‐aryl decahydroacridines in solvent‐free condition was efficiently performed in the presence of MCM‐41‐SO₃H as a nanocatalyst and nanoreactor in good yields. The method provides several advantages such as low cost, operational and experimental simplicity, high yields, and short reaction times. J. Heterocyclic Chem., (2012).     

Eburneolins A and B,new withanolide glucosides from Tricholepis eburnea

Eburneolins A (1) and B (2), new withanolide glucosides, have been isolated from the n-butanolic fraction of the 75% methanolic extract of aerial parts of Tricholepis eburnea. Their structures were elucidated through spectroscopic analysis including ESI-MS, 2D NMR and acid hydrolysis.     

Ultra‐small and highly dispersed Pd nanoparticles inside the pores of ZIF‐8: Sustainable approach to waste‐minimized Mizoroki–Heck cross‐coupling reaction based on reusable heterogeneous catalyst

The rapid development of nanomaterials, particularly advanced hybrid nanoparticles, has made new opportunities for the design and fabrication of high‐performance metal‐based catalysts. However, generating metal nanoparticles of desired size without aggregation is an important challenge for enhancing the catalytic activity of metal nanoparticles supported in the host matrix. In this work, a hybrid nanoporous material, namely Pd nanoparticles@N‐heterocyclic carbene@ZIF‐8, with a high internal surface area was successfully prepared using a dispersed anionic sulfonated N‐heterocyclic carbene–Pd(II) precursor inside the cavities of zeolitic imidazolate framework (ZIF‐8) using an impregnation approach followed by reduction with NaBH₄. The anionic sulfonated N‐heterocyclic carbene was found to be a superb ligand for the stabilization of Pd nanoparticles in the pores of ZIF‐8. The resulting system was applied to the Mizoroki–Heck cross‐coupling reaction, in which the catalyst showed high catalytic activity under mild reaction conditions.     

Magnetic Graphene Oxide Anchored Sulfonic Acid as a Novel Nanocatalyst for the Synthesis of N‐aryl‐2‐amino‐1,6‐naphthyridines

Magnetic graphene oxide functionalized with sulfonic acid (Fe₃O₄‐GO‐SO₃H) was used as a new recyclable nanocatalyst for one‐pot synthesis of N‐aryl‐2‐amino‐1,6‐naphthyridine derivatives under solvent free conditions. The catalyst could be easily recovered from the reaction mixture by an external magnet and reused without significant decrease in activity even after 4 runs. This nanocatalyst exhibited better activities to other commercially available sulfonic acid catalysts.     

Coagulansins A and B,New Withanolides from Withania coagulans Dunal

Coagulansins A ( 1 ) and B ( 2 ), two new withanolides, were isolated from the CHCl₃‐soluble fraction of Withania coagulans Dunal , along with two known withanolides, coagulin R and withanolide P. Their structures were assigned by means of ¹H‐ and ¹³C‐NMR spectra, DEPT, and ¹H,¹H‐COSY, NOESY, HMQC, and HMBC experiments.     

Numerical solution of nonlinear and non-isothermal general rate model of reactive liquid chromatography

Abstract

A nonlinear general rate model (GRM) of liquid chromatography is formulated to analyze the influence of temperature variations on the dynamics of multi-component mixtures in a thermally insulated liquid chromatographic reactor. The mathematical model is formed by a system of nonlinear convection–diffusion reaction partial differential equations (PDEs) coupled with nonlinear algebraic equations for reactions and isotherms. The model equations are solved numerically by applying a semi-discrete high-resolution finite volume scheme (HR-FVS). Several numerical case studies are conducted for two different types of reactions to demonstrate the influence of heat transfer on the retention time, separation, and reaction. It was found that the enthalpies of adsorption and reaction significantly influence the reactor performance. The ratio of density time heat capacity of solid and liquid phases significantly influences the magnitude and velocity of concentration and thermal waves. The results obtained could be very helpful for further developments in non-isothermal reactive chromatography and provide a deeper insight into the sensitivity of chromatographic reactor operating under non-isothermal conditions.     

Very fast and efficient synthesis of some novel substituted 2-arylbenzimidazoles in water using ZrOCl2·nH2O on montmorillonite K10 as catalyst

Abstract  A simple and eco-friendly protocol for the synthesis of some novel substituted 2-arylbenzimidazoles was developed. In this process, these compounds were prepared in water as the solvent using ZrOCl₂·nH₂O supported on montmorillonite K10 as an efficient water tolerating Lewis acid. The reaction was performed under mild conditions with good to excellent yields and remarkable chemoselectivity in the absence of any byproduct. Graphical Abstract        

New flavonoids from <Emphasis Type="Italic">Punica granatum</Emphasis> flowers

Two new flavonoids were isolated from the flowers of Punica granatum Linn. (Punicaceae) along with the known compounds ellagic acid, gallic acid, sucrose, and gallic acid glycoside. The structures of the new flavonoids have been characterized as 5,6,7,8,2′,3′,5′-heptahydroxy-4′-methoxyflavanone (punicaflavanol) and 5,6,7,8,2′,5′-hexahydroxy-4′-methoxyflavanone-7-β-D-xylopyranoside (granatumflavanyl xyloside) on the basis of spectral data analyses and chemical reactions.     

Phenolic constituents from Perovskia atriplicifolia

Perovskoate, an isorinic acid derivative (1) and perovskoside, the catechol derivative (2) have been isolated from the ethyl acetate soluble fraction of the whole plant of Perovskia atriplicifolia and assigned the structure 3(7-hydroxyphenyl)-2-hydroxy propanoic acid; (R)-form, 2-O-(6',7'-dihydroxy-E-cinnamoyl) (1) and 2-methoxy-4-(undecyl-4'-O-beta-D-glucopyranosyl) phenol (2). In addition, caffeic acid (3) and ferulic acid (4) have been reported for the first time from this species. The structures of these compounds were assigned on the basis of 1D and 2D NMR techniques. The compound 1 showed significant inhibitory activity against lipoxygenase and weak to moderate activity against cholinesterases.