Xiaojie Xu

Flavonoids from Ziziphus jujuba Mill var. spinosa

Abstract Eight flavonoid compounds were isolated from the seeds of Ziziphus jujuba Mill var. Spinosa . On the basis of chemical and spectral analyses their structures were elucidated as swertish ( 1 ), puerarin ( 2 ), 6‴-feruloylspinosin ( 3 ), apigenin-6- C -β- d -glucopyranoside ( 4 ), spinosin ( 5 ), 6‴-feruloylisospinosin ( 6 ), isospinosin ( 7 ), and isovitexin-2″- O -β- d -glucopyranoside ( 8 ). Flavonoids 6 and 7 are novel compounds. Rotamers exist for compounds 1 , 3 and 5 , which are reported for the first time. Compounds 2 , 4 and 8 were isolated from this plant for the first time. Spinosin and swertish possess significant sedative activity.

Protein molecular dynamics with electrostatic force entirely determined by a single Poisson-Boltzmann calculation.

The electrostatic force including the intramolecular Coulombic interactions and the electrostatic contribution of solvation effect were entirely calculated by using the finite difference Poisson‐Boltzmann method (FDPB), which was incorporated into the GROMOS96 force field to complete a new finite difference stochastic dynamics procedure (FDSD). Simulations were performed on an insulin dimer. Different relative dielectric constants were successively assigned to the protein interior; a value of 17 was selected as optimal for our system. The simulation data were analyzed and compared with those obtained from 500‐ps molecular dynamics (MD) simulation with explicit water and a 500‐ps conventional stochastic dynamics (SD) simulation without the mean solvent force. The results indicate that the FDSD method with GROMOS96 force field is suitable to study the dynamics and structure of proteins in solution if used with the optimal protein dielectric constant. Proteins 2002;48:497–504.

NMR determination of the structure of Julibroside J1.

Julibroside J1 is a new triterpenoid saponin which contains one triterpene, two monoterpenes and nine sugar residues. The structure has been determined almost exclusively by high-resolution NMR methods. The 1H and 13C NMR spectra of Julibroside J1 C5D5N have been assigned by homonuclear and heteronuclear correlation experiments, such as COSY, CH-COSY, TOCSY, HMBC, HMQC-COSY, HMQC-TOCSY and NOESY. Anomeric configurations were obtained by combined use of 1JCH and 3JH1,H2 and NOESY data. The particular sugar residues were identified by utilizing 3JHH values obtained from TOCSY cross-peaks, NOE difference spectra, and several 1D-TOCSY spectra, and three-bond intra-ring cross-peaks from a HMBC spectrum. Linkage assignments were made using the HMBC spectrum, and supplemented by NOE data from the NOESY spectrum. The structure of Julibroside J1 was characterized as 3-O-[beta-D-xylopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->6) -beta-D- glucopyranosyl]-21-O-((6S)-2-trans-2-hydroxymethyl-6-methyl-6-O-[4-O-((6 S)- 2-trans-2,6-dimethyl-6-O-(6-deoxy-beta-D-glucopyranosyl)-2,7-octadien oyl)-6- deoxy-beta-D-glucopyranosyl]-2,7-octadienoyl)-acacic acid 28-O-(beta-D-glucopyranosyl-(1-->3)-[alpha-L-arabinofuranosyl-(1-->4)]- alpha-L-rhamnopyranosyl-(1-->2))-beta-D-glucopyranosyl ester.