[Density functional theory investigation on antioxidant activity of five flavonoids from Hebei Xiangju].

Five main flavonoids of Hebei Xiangju were studied using the Density Functional Theory (DFT) B3LYP method with 6-311 G (d) basis set．Their activities were analyzed based on molecular structure,bond dissociation energy (BDE),natural orbital charge distribution (NBO),bond order and the energy gap between HOMO and LUMO. The results showed that the existing of intra molecular hydrogen bond in B ring can improve the antioxidant activity of the flavonoids, at the same time, the hydroxyl groups on the glycosides do not have the activity of eliminating free radicals, but decrease the total molecular antioxidant activity. As a result, the antioxidant ability order of the five flavonoids compounds is luteolin< luteolin-7-O-glucoside< apigenin < acacetin < acacetin-7-O-glucose, which is agreement with the experimental conclusion reported in literature. The results showed that the DFT method can provide theoretical guidance for the selection of natural flavonoid antioxidants.

[Tracking analysis of three extraction processes of Arenaria Polytrichoides by Fourier transform infrared spectrocopy].

In order to develop a process analysis method to guide extraction process of Arenaria polytrichoides (AP) based on tracking analysis by Fourier transform infrared (FTIR), IR spectra of petroleum ether extracts (PE-E), ethyl acetate extracts (EtOAc-E), n-butanol extracts (n-BuOH-E) and water extracts (H2O-E) of AP from three extraction methods were recorded. The FTIR and corresponding second derivative infrared (SDIR) spectra were analyzed comparatively from two aspects, namely, different extracts from a same extraction process and the same extracts from different methods. The spectral analysis results show that different extracts obtained from a same extraction process have distinctly different spectral absorbance character. Although the IR spectral absorption characteristics of the same extracts from different methods are rather similar in holistic, some explicit spectral differences still could be found among each other. In extraction process one (M1), main flavonoids and their glycosides of AP migrated to EtOAc-E and the rest part of them shift to n-BuOH-E according to FTIR peaks such as 1,603 and 1,123 cm(-1). However, the circumstances in method two (M2) and method three (M3) were just the reverse. Moreover, a few flavonoid glycosides got into H2O-E. The relative content of all kinds of aglycones and higher saturated alkyl are much higher in EtOAc-E of M2 than that of M1 and M3 according to the relative absorption intensive of peak at 2,850 cm(-1). Similarly, n-BuOH-E of M3 has relative rich contents of glycosides: and polysaccharides than those of M1 and M2 by peaks, such as 1,066 and 2,927 cm(-1). These results demonstrate that the migration rules of AP components are not always same in different extrac- tion process. The substance migration information during the extraction process could be recorded and disclosed in an intuitive way by FTIR tracking analysis of corresponding extracts. Consequently, FTIR tracking analysis is a fast, efficient, low-carbon and environment-friendly process analysis method. The method has important macro guiding significance for quality control and process optimization of extraction and isolation process of medicinal plant including AP.

Induction of apoptosis by phenylisocyanate derivative of quercetin: involvement of heat shock protein.

Quercetin, a widely distributed bioflavonoid, inhibits the growth of various tumor cells. The present study was designed to investigate whether a novel quercetin derivative [phenylisocyanate of quercetin (PHICNQ)] exerts antitumor activity against K562 and CT26 tumor cell lines by inducing apoptosis, and to examine the possible mechanism in the phenomenon. The cell proliferation assay of K562 and CT26 tumor cells was determined by the trypan blue dye exclusion test. Apoptosis of PHICNQ-treated cells was determined by morphological analysis, agarose gel DNA electrophoresis and quantitated by flow cytometry after staining with propidium iodide. Cell cycle was evaluated by flow cytometry. The expression of heat shock protein 70 was checked by Western blot analysis. Our results showed that PHICNQ inhibited the proliferation of K562 and CT26 cells in a dose-dependent and time-dependent manner. PHICNQ was 308- and 73-fold more active on CT26 and K562 cells than quercetin, respectively. In addition to this cytostatic effect, treatment of K562 and CT26 tumor cells with PHICNQ induced apoptosis. PHICNQ treatment downregulated the expression of heat shock protein 70 more dramatically than quercetin treatment. These results suggest that PHICNQ is a more powerful antiproliferative derivative than quercetin, with cytostatic and apoptotic effects on K562 and CT26 tumor cells. PHICNQ may trigger apoptosis in tumor cells through inhibition of heat shock protein 70 synthesis and expression.