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- Alvebratt, Caroline, et al.
(författare)
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In Vitro Performance and Chemical Stability of Lipid-Based Formulations Encapsulated in a Mesoporous Magnesium Carbonate Carrier
- 2020
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Ingår i: Pharmaceutics. - : MDPI AG. - 1999-4923. ; 12:5
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Tidskriftsartikel (refereegranskat)abstract
- Lipid-based formulations can circumvent the low aqueous solubility of problematic drug compounds and increase their oral absorption. As these formulations are often physically unstable and costly to manufacture, solidification has been suggested as a way to minimize these issues. This study evaluated the physicochemical stability and in vitro performance of lipid-loaded mesoporous magnesium carbonate (MMC) particles with an average pore size of 20 nm. A medium chain lipid was loaded onto the MMC carrier via physical adsorption. A modified in vitro lipolysis setup was then used to study lipid release and digestion with 1H nuclear magnetic resonance spectroscopy. The lipid loading efficiency with different solidification techniques was also evaluated. The MMC, unlike more commonly used porous silicate carriers, dissolved during the lipolysis assay, providing a rapid release of encapsulated lipids into solution. The digestion of the dispersed lipid-loaded MMC therefore resembled that of a coarse dispersion of the lipid. The stability data demonstrated minor degradation of the lipid within the pores of the MMC particles, but storage for three months did not reveal extensive degradation. To conclude, lipids can be adsorbed onto MMC, creating a solid powder from which the lipid is readily released into the solution during in vitro digestion. The chemical stability of the formulation does however merit further attention.
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| 5. |
- Huang, Hao, 1988-, et al.
(författare)
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Polaron Disproportionation Charge Transport in a Conducting Redox Polymer
- 2017
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 121:24, s. 13078-13083
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Tidskriftsartikel (refereegranskat)abstract
- Herein we report a mechanistic study of the charge transport in poly-3-((2,5-hydroquinone)vinyl)-1H-pyrrole by conductance measurements at various temperatures performed in situ during doping of the polypyrrole backbone in contact with an aqueous electrolyte. Charge transport was found to occur by electron hopping with associated electron transfer activation energies in the range of 0.08-0.2 eV. In situ electron paramagnetic resonance experiments indicated polarons as the dominant charge carriers and the charge transport was found to follow a second-order dependence with respect to the number of accumulated charges. Based on the findings, we present a polaron comproportionation/disproportionation model for electron conduction in poly-3-((2,5-hydroquinone)vinyl)-1H-pyrrole, thus, providing a complement to existing models for charge propagation in conducting polymers.
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| 6. |
- Huang, Hao, 1988-, et al.
(författare)
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Potential-tuning in quinone-pyrrole dyad-based conducting redox polymers
- 2021
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 389, s. 19099-19108
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Tidskriftsartikel (refereegranskat)abstract
- In this study, conducting redox polymers (CRPs), which consist of a polypyrrole conducting polymer backbone with attached quinone pendant groups, have been explored as electrode materials for organic batteries. A modular organic synthetic approach is presented that allows the assembly of pyrrole and quinone units into quinone-pyrrole dyads and modifying the dyads by varying the substitution pattern on the quinone moiety. These dyad monomers were copolymerized electrochemically with pyrrole to yield the CRPs with quinone formal potentials varying within a 0.6 V range. With access to CRP materials with tunable quinone formal potentials an all-organic water-based battery was constructed by choosing CRPs with different quinone potentials as anode and cathode material. Galvanostatic charge-discharge of the cell showed that the cell potentials coincided well with the difference in redox potential between the quinone substituents used in the anode and cathode CRP.
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| 7. |
- Naranjani, Benyamin, et al.
(författare)
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Numerical simulation of peristalsis to study co-localization and intestinal distribution of a macromolecular drug and permeation enhancer
- 2023
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier. - 0141-8130 .- 1879-0003. ; 240
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Tidskriftsartikel (refereegranskat)abstract
- In this work, simulations of intestinal peristalsis are performed to investigate the intraluminal transport of macromolecules (MMs) and permeation enhancers (PEs). Properties of insulin and sodium caprate (C10) are used to represent the general class of MM and PE molecules. Nuclear magnetic resonance spectroscopy was used to obtain the diffusivity of C10, and coarse-grain molecular dynamics simulations were carried out to estimate the concentration-dependent diffusivity of C10. A segment of the small intestine with the length of 29.75 cm was modeled. Peristaltic speed, pocket size, release location, and occlusion ratio of the peristaltic wave were varied to study the effect on drug transport. It was observed that the maximum concentration at the epithelial surface for the PE and the MM increased by 397 % and 380 %, respectively, when the peristaltic wave speed was decreased from 1.5 to 0.5 cm s−1. At this wave speed, physiologically relevant concentrations of PE were found at the epithelial surface. However, when the occlusion ratio is increased from 0.3 to 0.7, the concentration approaches zero. These results suggest that a slower-moving and more contracted peristaltic wave leads to higher efficiency in transporting mass to the epithelial wall during the peristalsis phases of the migrating motor complex.
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| 8. |
- Norrehed, Sara, 1982-, et al.
(författare)
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Formation of persistent organic diradicals from N,N'-diphenyl-3,7- diazacyclooctanes
- 2019
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Ingår i: Monatshefte fuer Chemie. - Vienna : Springer. - 0026-9247 .- 1434-4475. ; 150:1, s. 77-84
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Tidskriftsartikel (refereegranskat)abstract
- N,N'-Diphenyl-3,7-diazacyclooctane and structurally related N,N'-diphenylbispidine derivatives react with silver(I) ions in a high-yielding C–C coupling reaction to produce dication–diradical species, with the silver ions serving a double function both as template and as an oxidant. The resulting bis(benzidino)phane derivatives are persistent organic radicals, stable for several months in solution as well as in the solid state, at room temperature and above, as well as being exposed to the atmosphere. The molecular structure features a double-decker cyclophane motif, stabilized by intramolecular π-dimerization of two delocalized benzidinium radical segments. Intermolecular π-dimers are formed in the solid state.
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| 12. |
- Umereweneza, Daniel
(författare)
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Discovery of Secondary Metabolites from Rwandese Medicinal Plants : Isolation, Characterization and Biological Activity
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plants have served as the principal source of medicines in different parts of the world through the ages. Herb-derived medicines have been used as decoctions, infusions, tinctures or single substance drugs. Due to their impressive possibility of diversification, plants have also provided an immense universe of creativity for synthetic chemists, who constantly make useful new molecules inspired by the natural molecular architecture.The goal of this thesis work was to investigate secondary metabolites isolated from selected Rwandese medicinal plants. It focused specifically on the isolation, the characterization and the determination of the biological activity of natural products. The investigated plants belong to the families of Myrtaceae (Eucalyptus melliodora and Eucalyptus anceps), Fabaceae (Eriosema montanum), Lamiaceae (Clerodendrum myricoides) and Asteraceae (Senecio mannii). These were selected from the Rwandese flora based on information collected from traditional healers, and from the literature. The study made use of chromatographic, spectroscopic and spectrometric methods for separation, purification and structure elucidation of the plant constituents.In paper I, the chemical composition and antifungal activity of essential oils of E. melliodora and E. anceps were discussed. The essential oils were composed of mono- and diterpenes, and their alcohol derivatives. The essential oil mixtures exhibited antifungal activity against food spoilage fungi.In paper II, E. montanum was investigated and a total of 20 compounds were isolated including two new prenylated dihydrochalcones and eighteen known secondary metabolites. Their antibacterial activities and cytotoxicity were determined. In paper III, the isolation of three new and two known iridoid glycosides from C. myricoides was reported along with the antiviral activities of the crude extract and of the isolates. In paper IV, the phytochemical investigation of S. mannii was reported. It afforded one new silphiperfolanol angelate ester, two new macrocyclic pyrrolizidine alkaloids, and five known secondary metabolites. Two new synthetic derivatives were obtained by structural modification of 2-angeloyloxy-5,8-dihydroxypresilphiperfolane. The relative stereochemistry of senaetnine was investigated by NAMFIS and confirmed to be 7R, 12R, and 13R.The new compounds isolated in this study have shown biological activities, and may provide lead compounds for drug discovery and technological applications.
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