scholarly journals Competitive cocrystallization and its application in the separation of flavonoids

IUCrJ ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 195-207
Author(s):  
Yanming Xia ◽  
Yuanfeng Wei ◽  
Hui Chen ◽  
Shuai Qian ◽  
Jianjun Zhang ◽  
...  
Keyword(s):  
Free Energy ◽  
Formation Constant ◽  
Energy Gap ◽  
Hirshfeld Surface ◽  
Methanol Solution ◽  
Model Compounds ◽  
Electronic Density ◽  
Chemical Structures ◽  
Similar Chemical ◽  
Interaction Contribution

Recently, cocrystallization has been widely employed to tailor physicochemical properties of drugs in the pharmaceutical field. In this study, cocrystallization was applied to separate natural compounds with similar structures. Three flavonoids [baicalein (BAI), quercetin (QUE) and myricetin (MYR)] were used as model compounds. The coformer caffeine (CAF) could form cocrystals with all three flavonoids, namely BAI–CAF (cocrystal 1), QUE–CAF (cocrystal 2) and MYR–CAF (cocrystal 3). After adding CAF to methanol solution containing MYR and QUE (or QUE and BAI), cocrystal 3 (or cocrystal 2) preferentially formed rather than cocrystal 2 (or cocrystal 1), indicating that flavonoid separation could be achieved by competitive cocrystallization. After co-mixing the slurry of two flavonoids with CAF followed by centrifugation, the resolution ratio that could be achieved was 70–80% with purity >90%. Among the three cocrystals, cocrystal 3 showed the lowest formation constant with a negative Gibbs free energy of nucleation and the highest energy gap. Hirshfeld surface analysis and density of states analysis found that cocrystal 3 had the highest strong interaction contribution and the closest electronic density, respectively, followed by cocrystal 2 and cocrystal 1, suggesting CAF could competitively form a cocrystal with MYR much more easily than QUE and BAI. Cocrystallization is a promising approach for green and effective separation of natural products with similar chemical structures.

scholarly journals Synthesis and Biological Activity of New Brassinosteroid Analogs of Type 24-Nor-5β-Cholane and 23-Benzoate Function in the Side Chain

2021 ◽  
Vol 22 (9) ◽  
pp. 4808
Author(s):  
Nitza Soto ◽  
Karoll Ferrer ◽  
Katy Díaz ◽  
César González ◽  
Lautaro Taborga ◽  
...  
Keyword(s):  
Good Alternative ◽  
Positive Control ◽  
Starting Material ◽  
Chemical Structures ◽  
High Reaction ◽  
Similar Chemical ◽  
Synthetic Procedure ◽  
Hyodeoxycholic Acid ◽  
External Stresses

Brassinosteroids are polyhydroxysteroids that are involved in different plants’ biological functions, such as growth, development and resistance to biotic and external stresses. Because of its low abundance in plants, much effort has been dedicated to the synthesis and characterization of brassinosteroids analogs. Herein, we report the synthesis of brassinosteroid 24-nor-5β-cholane type analogs with 23-benzoate function and 22,23-benzoate groups. The synthesis was accomplished with high reaction yields in a four-step synthesis route and using hyodeoxycholic acid as starting material. All synthesized analogs were tested using the rice lamina inclination test to assess their growth-promoting activity and compare it with those obtained for brassinolide, which was used as a positive control. The results indicate that the diasteroisomeric mixture of monobenzoylated derivatives exhibit the highest activity at the lowest tested concentrations (1 × 10−8 and 1 × 10−7 M), being even more active than brassinolide. Therefore, a simple synthetic procedure with high reaction yields that use a very accessible starting material provides brassinosteroid synthetic analogs with promising effects on plant growth. This exploratory study suggests that brassinosteroid analogs with similar chemical structures could be a good alternative to natural brassinosteroids.

Diffusional distortion of the free‐energy gap law

1995 ◽  
Vol 103 (18) ◽  
pp. 7927-7933 ◽  
Author(s):  
A. I. Burshtein
Keyword(s):  
Free Energy ◽  
Energy Gap ◽  
Energy Gap Law

Molecular Motion Analysis of 5CB in PDLCs Using Solid-State 13C NMR Relaxation Spectroscopy

1993 ◽  
Vol 47 (7) ◽  
pp. 933-941 ◽  
Author(s):  
Karen L. Buchert ◽  
Jack L. Koenig ◽  
Shi-Qing Wang ◽  
John L. West
Keyword(s):  
Liquid Crystal ◽  
Solid State ◽  
Polymer Matrix ◽  
Nmr Relaxation ◽  
Domain Size ◽  
Chemical Structures ◽  
Similar Chemical ◽  
Polymer Dispersed ◽  
Submicron Droplets ◽  
Significant Change

In samples of polymer-dispersed liquid crystals (PDLCs), submicron droplets of liquid crystal reside within a polymer matrix. By the use of the cross polarization technique for solid-state 13C NMR spectroscopy, the NMR spectrum of the liquid crystal can be obtained without interference from the polymer spectrum, even though the two materials have some similar chemical structures. Both 13C T1 and 13C T1 ρ relaxation experiments were performed on a PDLC system of 5CB in epoxy as a function of 5CB domain size. The 13C T1 relaxation constants and the localized motions they measure showed no significant change over the liquid crystal domain size studied. However, the 13C T1 ρ relaxation constants and the segmental motions of molecules they measure revealed a significant change over the liquid crystal domain size studied. Therefore, the 13C T1 ρ values can be used to determine the change in mobility of the molecular segments of the SCB molecules resulting from increased interaction between the liquid crystal and the polymer matrix and to further understand the importance of the molecular motions of the liquid crystal in the switching phenomenon for PDLC materials.

CHLORINE GAS SENSING OF SnO2 NANOCLUSTERS AS A FUNCTION OF TEMPERATURE: A DFT STUDY

2019 ◽  
Vol 26 (04) ◽  
pp. 1850172
Author(s):  
MUDAR AHMED ABDULSATTAR ◽  
ADEEBH L. RESNE ◽  
SHROK ABDULLAH ◽  
RIYADH J. MOHAMMED ◽  
NOON KADHUM ALARED ◽  
...  
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Density Functional ◽  
Tin Dioxide ◽  
Energy Gap ◽  
Gas Sensing ◽  
Free Energy Calculations ◽  
Measured Temperature ◽  
Chlorine Molecule ◽  
Chlorine Gas

Density functional theory combined with Gibbs free energy calculations is used to study the sensing behavior of tin dioxide (SnO[Formula: see text] clusters towards chlorine gas molecules. Studied SnO2 clusters’ results show the known property of tin dioxide being an oxygen-deficient semiconductor with the preferred stoichiometry SnO[Formula: see text]. The kind of reactions that result in sensing Cl2 molecules is investigated. These include oxygen replacement, chlorine molecule dissociation and van der Waals attachment. Oxygen replacement shows an increase in energy gap which is the case experimentally. Optimum sensing operating temperature towards Cl2 molecules that results from the intersection of the highest SnO2 adsorption and desorption Gibbs free energy lines is at 275∘C in agreement with the experimentally measured temperature of 260∘C.

scholarly journals Crystal structure, Hirshfeld surface analysis and interaction energy and DFT studies of 2-(2,3-dihydro-1H-perimidin-2-yl)-6-methoxyphenol

2020 ◽  
Vol 76 (5) ◽  
pp. 605-610
Author(s):  
Ballo Daouda ◽  
Nanou Tiéba Tuo ◽  
Tuncer Hökelek ◽  
Kangah Niameke Jean-Baptiste ◽  
Kodjo Charles Guillaume ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Surface Analysis ◽  
Density Functional ◽  
Energy Gap ◽  
Crystal Packing ◽  
Hirshfeld Surface ◽  
Van Der Waals Interactions ◽  
Hirshfeld Surface Analysis ◽  
Functional Theory ◽  
Compound C

The title compound, C18H16N2O2, consists of perimidine and methoxyphenol units, where the tricyclic perimidine unit contains a naphthalene ring system and a non-planar C4N2 ring adopting an envelope conformation with the NCN group hinged by 47.44 (7)° with respect to the best plane of the other five atoms. In the crystal, O—HPhnl...NPrmdn and N—HPrmdn...OPhnl (Phnl = phenol and Prmdn = perimidine) hydrogen bonds link the molecules into infinite chains along the b-axis direction. Weak C—H...π interactions may further stabilize the crystal structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H...H (49.0%), H...C/C...H (35.8%) and H...O/O...H (12.0%) interactions. Hydrogen bonding and van der Waals interactions are the dominant interactions in the crystal packing. Computational chemistry indicates that in the crystal, the O—HPhnl...NPrmdn and N—HPrmdn...OPhnl hydrogen-bond energies are 58.4 and 38.0 kJ mol−1, respectively. Density functional theory (DFT) optimized structures at the B3LYP/ 6–311 G(d,p) level are compared with the experimentally determined molecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

scholarly journals Dinucleoside polyphosphates act as 5’-RNA caps in Escherichia coli

2019 ◽  
Author(s):  
Oldřich Hudeček ◽  
Roberto Benoni ◽  
Martin Culka ◽  
Martin Hubálek ◽  
Lubomír Rulíšek ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Rna Stability ◽  
E Coli ◽  
Chemical Structures ◽  
Additional Layer ◽  
Similar Chemical ◽  
Decapping Enzyme ◽  
Almost All ◽  
Dinucleoside Polyphosphates ◽  
Rna Caps

Dinucleoside polyphosphates (NpnNs), discovered more than 50 years ago,1 are pleiotropic molecules present in almost all types of cells.2 It has been shown that their intracellular concentration can under stress conditions increase from the µM to mM range 2,3. However, the cellular roles and mechanisms of action of NpnNs are still speculative4,5. They have never been considered as part of the RNA, even though they have similar chemical structures as already known RNA caps, such as the nicotinamide adenine dinucleotide (NAD)6-8 and 7-methylguanylate cap9. Here, we show that both methylated and non-methylated Npn Ns serve as RNA caps in Escherichia coli (E. coli). NpnNs are excellent substrates for T7 and E. coli RNA polymerases (RNAP) and efficiently initiate transcription. Further, we demonstrate that the E. coli decapping enzyme RNA 5’ pyrophosphohydrolase (RppH) is able to remove the NpnNs-cap from the RNA. RppH was, however, not able to cleave the methylated forms of the NpnN-caps, suggesting that the methylation adds an additional layer to the RNA stability regulation. Our work introduces an original perspective on the chemical structure of RNA in prokaryotes and the function of RNA caps. This is the first evidence that small molecules like NpnNs can act in cells via their incorporation into RNA and influence the cellular metabolism.

scholarly journals Effects of Petroleum-Based Oils as Dispersing Aids on Physicochemical Characteristics of Magnetorheological Elastomers

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7026
Author(s):  
Norizatie Muhammad Zaki ◽  
Nurul Azhani Yunus ◽  
Muhamad Shakir Yusoff ◽  
Saiful Amri Mazlan ◽  
Siti Aishah Abdul Aziz ◽  
...  
Keyword(s):  
Magnetic Particles ◽  
Physicochemical Characteristics ◽  
Magnetorheological Elastomers ◽  
Weight Percentage ◽  
Chemical Structures ◽  
Microstructure Observation ◽  
Curing Characteristics ◽  
Similar Chemical ◽  
Low Performance ◽  
Light Mineral

This paper investigated the effects of petroleum-based oils (PBOs) as a dispersing aid on the physicochemical characteristics of natural rubber (NR)-based magnetorheological elastomers (MREs). The addition of PBOs was expected to overcome the low performance of magnetorheological (MR) elastomers due to their inhomogeneous dispersion and the mobility of magnetic particles within the elastomer matrix. The NR-based MREs were firstly fabricated by mixing the NR compounds homogeneously with different ratios of naphthenic oil (NO), light mineral oil (LMO), and paraffin oil (PO) to aromatic oil (AO), with weight percentage ratios of 100:0, 70:30, 50:50, and 30:70, respectively. From the obtained results, the ratios of NO mixed with low amounts of AO improved the material physicochemical characteristics, such as thermal properties. Meanwhile, LMO mixed the AO led to the best results for curing characteristics, microstructure observation, and magnetic properties of the MREs. We found that the LMO mixed with a high content of AO could provide good compatibility between the rubber molecular and magnetic particles due to similar chemical structures, which apparently enhance the physicochemical characteristics of MREs. In conclusion, the 30:70 ratio of LMO:AO is considered the preferable dispersing aid for MREs due to structural compounds present in the oil that enhance the physicochemical characteristics of the NR-based MREs.

Surfaces, Interfaces, and Changing Shapes in Multilayered Films

MRS Bulletin ◽  
1999 ◽  
Vol 24 (2) ◽  
pp. 39-43 ◽  
Author(s):  
Daniel Josell ◽  
Frans Spaepen
Keyword(s):  
Free Energy ◽  
Excess Free Energy ◽  
External Pressure ◽  
Electronic Density ◽  
Spherical Drop ◽  
Crystal Anisotropy ◽  
Fundamental Quantity ◽  
The Difference ◽  
Image Position ◽  
Work Done

It is generally recognized that the capillary forces associated with internal and external interfaces affect both the shapes of liquid-vapor surfaces and wetting of a solid by a liquid. It is less commonly understood that the same phenomenology often applies equally well to solid-solid or solid-vapor interfaces.The fundamental quantity governing capillary phenomena is the excess free energy associated with a unit area of interface. The microscopic origin of this excess free energy is often intuitively simple to understand: the atoms at a free surface have “missing bonds”; a grain boundary contains “holes” and hence does not have the optimal electronic density; an incoherent interface contains dislocations that cost strain energy; and the ordering of a liquid near a solid-liquid interface causes a lowering of the entropy and hence an increase in the free energy. In what follows we shall show how this fundamental quantity determines the shape of increasingly complex bodies: spheres, wires, thin films, and multilayers composed of liquids or solids. Crystal anisotropy is not considered here; all interfaces and surfaces are assumed isotropic.Consideration of the equilibrium of a spherical drop of radius R with surface free energy γ shows that pressure inside the droplet is higher than outside. The difference is given by the well-known Laplace equation:This result can be obtained by equating work done against internal and external pressure during an infinitesimal change of radius with the work of creating a new surface.

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