A LC/UV/Vis method for determination of cyanocobalamin (VB12) in multivitamin dietary supplements with on-line sample clean-up

A HPLC-UV/Vis method using a two-column strategy with a switching valve for on-line sample cleanup was developed for the determination of cyanocobalamin (CN–Cbl/Vitamin B12) in multivitamin dietary supplement tablets. The method uses two columns: an Agilent Zorbax C8 (150 mm 4.6 mm, 5 mm particle size) reversed-phase column and a Waters Symmetry C18 (150 mm 4.6 mm, 5 mm particle size) reversed-phase column. Chromatographic separation was achieved using a programmed gradient mobile phase consisting of (A) 0.1% formic acid in water and (B) 0.1% formic acid in acetonitrile. Because of the low levels of Vitamin B12 in the samples, large injection volumes, and thus much interfering material, must be used to exceed the limit of quantitation (LOQ) by UV detection. A switching valve was used to divert most of these early eluting interfering materials to waste, effecting on-line sample clean-up without excessive sample preparation steps. The recovery of CN–Cbl in the method was 99.5% and the LOQ was 10 ng per injection. The method was successfully applied to the analysis of the NIST SRM 3280 multivitamin/multimineral dietary supplement tablet. The method is specific, precise, and accurate for the intended use. Compared to off-line sample clean-up procedures, it offers the advantage of being easier, more economical, and less time-consuming

A novel platinum compound inhibits constitutive Stat3 signaling and induces cell cycle arrest and apoptosis of malignant cells

Previous studies have established constitutive activation of Stat3 protein as one of the molecular changes required for tumorigenesis. To develop novel therapeutics for tumors harboring constitutively active Stat3, compounds from the NCI 2000 diversity set were evaluated for inhibition of Stat3 DNA-binding activity in vitro. Of these, a novel platinum (IV) compound, IS3 295, interacted with Stat3 and inhibited its binding to specific DNA-response elements. Further analysis suggested noncompetitive-type kinetics for the inhibition of Stat3 binding to DNA. In human and mouse tumor cell lines with constitutively active Stat3, IS3 295 selectively attenuated Stat3 signaling, thereby inducing cell growth arrest at G(0)/G(1) phase and apoptosis. Moreover, in transformed cells, IS3 295 repressed expression of cyclin D1 and bcl-x(L), two of the known Stat3-regulated genes that are overexpressed in malignant cells, suggesting that IS3 295 mediates anti-tumor cell activity in part by blocking Stat3-mediated subversion of cell growth and apoptotic signals. Together, our findings provide evidence for the inhibition of Stat3 activity and biological functions by IS3 295 through interaction with Stat3 protein. This study represents a significant advance in small molecule-based approaches to target Stat3 and suggests potential new applications for platinum (IV) complexes as modulators of the Stat3 pathway for cancer therapy

Electrophysiologie des protoplastes de chèvrefeuille (Lonicera spp.)

*INRA, centre d'Angers Diffusion du document : INRA, centre d'Anger

Electrophysiologie des protoplastes de chèvrefeuille (Lonicera spp.)

*INRA, centre d'Angers Diffusion du document : INRA, centre d'Anger