Tandem mass spectrometric fragmentation behavior of lignans, flavonoids and triterpenoids in Streblus asper.

RATIONALE: An unambiguous identification of compounds can be achieved by comparison of known fragmentation patterns. While the literature about fragmentation mechanisms of lignans, flavonoids and triterpenoids is few. So the present study analyses the fragmentation mechanisms of these compounds isolated from Streblus asper. METHODS: Electrospray ionization ion trap mass spectrometry (ESI-ITMS) and atmospheric pressure chemical ionization ion trap mass spectrometry (APCI-ITMS) were used to obtain the MS(n) spectra of the compounds. By analyzing the differences between the ions, the fragmentation mechanisms of these compounds were explored. RESULTS: Of the 29 compounds detected, 17, 7, and 5 were lignans, flavonoids and triterpenoids, respectively. The majority of lignans were found to give [M - H](-) ions of sufficient abundance for MS(n) analyses. The flavonoids were prone to the loss of CO and H2O. The triterpenoids always lost one formic acid molecule and two hydrogens, or one H2O from [M - H](-) to form the most abundant product ion in the MS(n) spectrum. CONCLUSIONS: ESI/APCI-ITMS were demonstrated to be fast, effective and practical tools to characterize the structures of flavonoids, triterpenoids and lignans. Results of the present study can help identify the analogous constituents by analyzing their MS(n) spectra.

[Studies on the polysaccharide SGPS2 from the fruits of Siraitia grosvenorii].

OBJECTIVE: To study the structure of the polysaccharides constituents in the fruits of Siraitia grosvenorii (Swingle) C. Jeffrey. METHODS: SGPS2 was purified by DEAE-cellulose and Sephadex G-200 column chromatography, the component and structure of SGPS2 were analyzed on the basis of spectral and chemical studies by HPLC, IR analysis, partial hydrolysis with acid, methylation analysis, GC and 13C-NMR. RESULTS: The molecular weight of SGPS2 was 650 000. Polysaccharide was composed of L- made up of (1 --> 2, 4) linked rhamnose, (1 --> 4) linked rhamnose residues in main chain; and (1 --> 2) linked rhamnose, (1 --> 3) linked rhamnose in side chains. Terminal residues attached main chain to rhamnose. CONCLUSION: SGPS2 was composed of rhamnose and curonic acid.

A new dilactone from the seeds of Gaultheria yunnanensis.

Gaultheriadiolide (1), a new compound, together with the known dauosterol (2), ginkgetin (3), myricetin (4), 6-ethyl-5-hydroxy-2,7-dimethoxy-1,4-naphthoquinone (5), ursolic acid (6), methyl salicylate 2-O-beta-D-xylosyl(1-->6)beta-D-glucopyranoside (7), and methyl salicylate 2-O-beta-D-glucopyranoside (8) were isolated from Gaultheria yunnanensis. The structure was elucidated on the basic of spectral analysis, especially 1D and 2D NMR. Primary bioassays showed that compound 1 had medium cytotoxic activity against HEp-2 and HepG2 Cells, with IC(50) of 23.337 microM and 29.4497 microM, respectively.