Purification and characterization of two grandiuvarones from Desmos chinensis leaves and their antimicrobial activities.

A novel aromatic compound, grandiuvarone B (5-acetoxy-3-benzoyloxymethyl-5H-oxepin-4-one), along with a known compound grandiuvarone A (5-acetoxy-6-benzoyloxymethyl-5H-oxepin-4-one) were isolated from methanol extracts of Desmos chinensis leaves. Their structures were determined by various spectroscopic techniques including nuclear magnetic resonance (NMR), high-resolution electrospray ionisation mass spectrometry (HR-ESI-MS) and circular dichroism (CD). Grandiuvarone A and grandiuvarone B are isomers and the S configuration of grandiuvarone B was reported for the first time. We then determined their antifungal activity against Aspergillus flavus. Results revealed that grandiuvarone B exhibited better antifungal activity against A. flavus, with MIC values of 0.01 mg/mL compared to grandiuvarone A (MIC values of 0.02 mg/mL). In the presence of each active compound at 160 µg/g of aquafeed, A. flavus growth was completely inhibited. Grandiuvarone B also showed antibacterial activity against the plant pathogen Ralstonia solanacearum.

Column selection approach for related substances determination of progesterone by high-performance liquid chromatography.

In this study, HPLC-MS/MS with triple-quadrupole tandem mass spectrometer was used to analyze the base-catalyzed thermal degradation derivative of progesterone in Chinese Pharmacopoeia. The full-scan spectrometry revealed that the degradation product was an isomer of progesterone, it was proposed as impurity M ((17α)-pregn-4-ene-3,20-dione) in European Pharmacopoeia, and both the derivative and progesterone were neutral molecules. Four kinds of chromatographic column characterization databases including PQRI database using Snyder/Dolan method, the USP chromatographic column database using the SRM 870 tests, the Tanaka/Euerby approach within the ACD program, and the Hoogmartens approach were compared. Combing the principles of column characterization databases with the system requirement of progesterone-related substances testing, a suitable PQRI-based method was finally set up for progesterone-related substances detecting. Our results indicated that PQRI system of Snyder/Dolan method was the most suitable system for related substances detection of progesterone.

Coexistence of and interaction relationships between an aflatoxin-producing fungus and a bacterium.

The interactions between aflatoxin-producing fungi and bacteria have opened up a new avenue for identifying biological agents suitable for controlling aflatoxin contamination. In this study, we analysed the interactions between A. flavus and the bacterium Burkholderia gladioli M3 that coexist in rice that is naturally contaminated with A. flavus. Our results showed that a cell-free culture filtrate (CCF) and the metabolite bongkrekic acid of the M3 strain potently suppressed the mycelial growth and spore production, and then affected the production of aflatoxin of A. flavus. Bongkrekic acid secreted by the M3 strain exhibited higher antifungal activity than did analogues. The CCF of the M3 strain and its metabolite bongkrekic acid can inhibit the growth of A. flavus, but the metabolites of A. flavus, aflatoxins, exerted no inhibitory effect on the growth of the M3 strain. Furthermore, we determined that the M3 cells could use the dead mycelia of A. flavus as energy sources for reproduction, while A. flavus could not grow in a solution containing dead M3 cells. In summary, these results indicated that B. gladioli has a competitive advantage in survival when it coexists with its fungal partner A. flavus.

Separation of naproxen enantiomers by supercritical/subcritical fluid chromatography.

An isocratic supercritical/subcritical fluid chromatography method for the separation of naproxen enantiomers on the Kromasil CHI-TBB column was investigated. The mobile phase was composed of supercritical CO2 with 2-propanol as modifier. The experimental conditions were temperature 293 K-323 K, pressure 9.4 MPa-21.3 MPa, and 2-propanol concentration 6%-15% (by mass), respectively. The enthalpic contribution to the overall enantiomer transfer energy was more important than the entropic contribution in the temperature range examined. The preferred operation conditions were 293 K, 9.4 MPa, and the concentration of 2-propanol in the mobile phase 11% (by mass).

[Extra-thermodynamic properties of 2-arylpropionic acids on a chiral-AGP column by high performance liquid chromatography].

The effect of temperature (274-313 K) on the chromatographic behavior of naproxen and ibuprofen on a Chiral-AGP column was investigated with a mobile phase consisting of 50 mmol/L phosphate buffer (pH 6.41) and 0.5% (or 1.0%, v/v) 1-propanol. Higher temperature was found disadvantageous to the enantiomeric separation. With temperature increased, the retention time, resolution and selectivity of the chiral separation were decreased. The resolution of naproxen was larger than that of ibuprofen in all cases. When naproxen and ibuprofen enantiomers were entirely separated by the mobile phase containing 1.0% 1-propanol, the maximum temperatures allowed were 298 K and 288 K, respectively. All of the Van' t Hoff plots of the In k vsrsus 1/T were found to have good linearity, with the correlation coefficients better than 0.99 in all cases. The thermodynamic parameters (changes of enthalpy, i. e., deltaH0, for the transfer of enantiomers from the mobile phase to the stationary phase and differences of enthalpy and entropy changes, i. e., deltaS,R deltaH0 and deltaS,R deltaS0) were calculated. In general, in the temperature range examined the enthalpic contribution to the overall enantiomer transfer energy was found to be more significant than the entropic one.