Precision studies in supramolecular chemistry: a 1H NMR study of hydroxymethoxyacetophenone/β-cyclodextrin complexes

Bioassay-directed isolation of falcarindiol and isoacetovanillon from Pycnocycla caespitosa based on KCl-induced contraction in rat uterus smooth muscles

Hydroalcoholic extract and essential oil of aerial parts of Pycnocycla caespitosa have spasmolytic activity on rat ileum contractions. The objective of this research was to separate fractions of total hydroalcoholic extract of P. caespitosa guided by their spasmolytic activity on rat uterus. Aerial parts of P. caespitosa were extracted with ethanol. The concentrated extract was subjected to column chromatography and thin layer chromatography (TLC) for isolation fractions, then one of the bioactive fractions was subjected to further isolation to find its active components. Five fractions were obtained (Fr.1-Fr.5) and their anti-spasmodic activities were examined on uterus contraction induced by KCl (80 mM) and compared with ritodrine. In addition, spasmolytic effect of Fr.4 (one of the bioactive fractions) was determined on rat uterus induced by oxytocin (0.0005 IU/mL) and compared with ritodrine. Hydroalcoholic extract of P. caespitosa (0.032-2 mg/mL) reduced the responses to KCl but the inhibitory effect was not complete with 2 mg/mL extract in the bath. Four fractions (Fr.1, Fr.2, Fr.3 and Fr.4) (32-500 μg/mL) inhibited rat uterus contractions on the uterus while Fr.4 was slightly more active than others (IC₅₀ = 146 ± 23 μg/mL). Falcarindiol and isoacetovanillone were identified from Fr.4 using phytochemical methods including high-performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR) and TLC. In conclusion, in this research bioactivity guided technique was successfully used for separation of active fraction of P. caespitosa. Falcarindiol and isoacetovanillone were identified from the active fraction which inhibited both tonic and rhythmic contractile responses in rat isolated uterus.

Tuning temperature responsive poly(2-alkyl-2-oxazoline)s by supramolecular host-guest interactions

A poly[(2-ethyl-2-oxazoline)-ran-(2-nonyl-2-oxazoline)] random copolymer was synthesized and its thermoresponsive behavior in aqueous solution modulated by the addition of different supramolecular host molecules. The macrocycles formed inclusion complexes with the nonyl aliphatic side-chains present in the copolymer, increasing its cloud point temperature. The extent of this temperature shift was found to depend on the cavitand concentration and on the strength of the host-guest complexation. The cloud point temperature could be tuned in an unprecedented wide range of 30 K by supramolecular interactions. Since the temperature-induced breakage of the inclusion complexes constitutes the driving force for the copolymer phase transition, the shift in cloud point temperature could be utilized to estimate the association constant of the nonyl side chains with the cavitands.

Mechanism study on pH-responsive cyclodextrin capped mesoporous silica: effect of different stalk densities and the type of cyclodextrin

Cyclodextrin (CD)-capped mesoporous silica nanoparticles (MSN) with pH-responsive properties were synthesized, but little research has been carried out to evaluate the impact of critical factors such as the stalk density and the type of CD on the pH-responsive release behavior. Here, the effect of different stalk densities on the pH-responsive release behavior was investigated. Either too low or too high density of the grafted p-anisidine stalk could result in poor cargo release, and the optimum stalk density for MSN was measured by thermal analysis, and found to be approximately 8.7 stalks nm(-2). To achieve effective release control, the CD capes, α-CD and β-CD, were also investigated. Isothermal titration calorimetry (ITC) analysis was employed to determine the formation constants (Kf) of the two CD with p-anisidine at different pH values. The results obtained showed that the complex of β-CD with p-anisidine had excellent pH-responsive behavior as it exhibited the largest changed formation constant (ΔKf) in different pH media. Furthermore, the pH-responsive mechanism between CD and p-anisidine molecules was investigated through ITC and a molecular modeling study. The release of antitumor drug DOX presents a significant prospect toward the development of pH-responsive nanoparticles as a drug delivery vehicle.

Phytochemical Profile of the Aerial Parts of Sedum sediforme and Anti-inflammatory Activity of Myricitrin

The aim of this study was to investigate the phytochemical profile of the methanol extract of the aerial parts of Sedum sediforme and to identify its secondary metabolites. By means of chromatographic separation and enrichment of compounds, HPLC-ESI-MS, HRMS, 1D-, 2D- NMR and/or comparison with reference compounds, three triterpenes, two sterols, ten flavonoids and twelve phenolic compounds were identified, together with two new compounds, i.e. (2 R*, 3 R*)-5,7-dihydroxy-2,3-dimethyl-4-chromanone-7- O-ß-D-glucoside (27) and butan-2- O-rutinoside (28). Out of the 29 identified secondary metabolites, 18 are described as ingredients of S. sediforme herein for the first time. Furthermore, myricitrin, one of the major constituents, was tested for its ability to inhibit different enzymes within the arachidonic acid cascade in order to determine its anti-inflammatory properties. Whereas there was only either weak or no inhibition of the microsomal prostaglandin E2 synthase-1 (mPGES-1) and the soluble epoxide hydrolase (sEH), myricitrin showed strong inhibition of 5-lipoxygenase (5-LO), with an IC50 of 7.8 ± 0.2 μM.