Observational characteristics of SiO masers around VX Sgr

SiO maser VLBA observations toward VX Sgr are performed at five epochs, and lots of maser spots are obtained. We make a statistical analysis on these spots. It is shown that the apparent sizes and the fluxes of maser spots decrease with increasing the distance from the central star. In addition, the similarity between the v = 1,2(J =1–0) spectrums increases with epochs, consistent with the full width at half maximum(FWHM), while the total fluxes increase. The results may be related to the changeable pumping mechanisms.

Three New C_(21) Steroidal Glycosides from Roots of Cynanchum otophyllum

Objective To investigate the chemical structures of glycosides in the roots of Cynanchum otophyllum(Asclepiadaceae) and to find new glycosides. Methods The total glycosides in the roots of C. olophyllum were separated by silica gel column chromatography. The structures of the resulting compounds were determined by NMR and FAB-MS spectra. Results Three C21 steroidal glycosides were separated. Their structures were determined as caudatin 3-O-(4-O-methyl-β-D-cymaropyranosyl)-(1→4)-ɑ-D-oleandropyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-ɑ-L-rhamnopyranoside(1), caudatin 3-O-β-D-digitoxopyranosyl-(1→4)-ɑ-D-oleandropyranosyl-(1→4)-β-Ddiginopyranosyl-(1→4)-β-D-glucopyranoside(2), and caudatin 3-O-β-D-diginopyranosyl-(1→4)-ɑ-D-oleandropyranosyl-(1→4)-ɑ-D-oleandropyranosyl-(1→4)-β-Dglucopyranoside(3), respectively. Conclusion Glycosides 1-3 are new compounds.

C_(21) Steroidal Glycosides from Acidic Hydrolysate of Cynanchum otophyllum

Objective To investigate the structures of compounds in the rhizome of Cynanchum otophyllum(Asclepiadaceae), and to find new C21 steroidal glycosides. Methods The ethyl acetate extract from the rhizome was subjected to acidic hydrolysis and isolated by column chromatography; The structures of the purified compounds were determined by spectral methods. Literature search confirmed whether those compounds were of new structures. Results Three compounds were isolated and their structures were deacetylmetaplexigenin 3-O-β-D-oleandropyranosyl-(1→4)-α-D-oleandropyranosyl-(1→4)-α-D-oleandropyranoside(1), deacetylmetaplexigenin 3-O-α-D-oleandropyranosyl-(1→4)-β-D-thevetopyranosyl-(1→4)-α-D-oleandropyranoside(2), and deacetylmeta-plexigenin 3-O-β-D-cymaropyranosyl-(1→4)-α-D-oleandropyranoside(3), respectively. Conclusion Compounds 1-3 are new compounds.

C_(21) Steroidal Saponins from Cynanchum otophyllum

Objective To study the chemical structures of saponins in the rhizome of Cynanchum otophyllum(Asclepiadaceae), and to find new compounds. Methods The total saponins of the rhizome were separated by silica gel column chromatography. The chemical structures of obtained compounds were determined by NMR and FAB-MS spectra. Results Three C21 steroidal saponins were separated. Their structures were determined as caudatin 3-O-β-D-glucopyranosyl-(1→4)-β-D-digitoxopyranosyl-(1→4)-β-D-diginopyranosyl-(1→4)-α-D-oleandropyranoside(1), caudatin 3-O-β-D-oleandropyranosyl-(1→4)-α-D-oleandropyranosyl-(1→4)-α-D-oleandropyranoside(2), and caudatin 3-O-β-D-glucopyranosyl-(1→4)-α-D-oleandropyranosyl-(1→4)-β-D-diginopyranosyl-(1→4)-α-D-oleandropyranoside(3), respectively. Conclusion Saponins 1-3 are new compounds.