Shi-Ji Xiao

Three new 1-(p-hydroxybenzyl)phenanthrenes from Bletilla striata.

Abstract Three new benzylphenanthrenes, named 1-(p-hydroxybenzyl)-4,7-dimethoxyphenanthrene-2-ol (1), 1-(p-hydroxybenzyl)-4,7-dimethoxyphenanthrene-2,8-diol (2), and 1-(p-hydroxybenzyl)-4,7-dimethoxyphenanthrene-2,6-diol (3), along with a known analog were isolated from tubers of Bletilla striata. The structures of these new compounds were established by means of HR-ESI-MS, 1D, and 2D NMR.

Polycyclic Spiro Lignans and Biphenyl Tetrahydrofuranone Lignans from Gymnotheca involucrata

Four rare polycyclic spiro lignans (1-4) and four new biphenyl tetrahydrofuranone lignans (5-8) were isolated from the whole plant of Gymnotheca involucrata. The structures of the new compounds were elucidated on the basis of detailed spectroscopic analysis and the absolute configuration of 1 was confirmed by single crystal X-ray diffraction. Bioassay results showed that compounds 2 and 6 exhibited weak antifungal activity against Uromyces viciae-fabae at 100 ppm in leaf-disc assays, while compound 3 demonstrated moderate insecticidal activity against Diabrotica balteata at 500 ppm in an artificial diet assay.

Strategy to Rapidly Discriminate Trace Isomeric Lignan Compounds from Gymnotheca Chinensis by Probe Electrospray Ionization Tandem Mass Spectrometry

Probe electrospray ionization (PESI) is a recently developed ionization technique based on electrospray ionization (ESI) that generates electrospray from the tip of a solid needle. High tolerance to salts, requirements of a trace amount of sample and direct ambient sampling are major advantages of PESI compared with conventional ESI. In this report, three pairs of isomeric lignans bearing tetrahydrofuran with variable conformations from Gymnotheca chinensis were investigated by probe electrospray tandem mass spectrometry (PESI-MS/MS) in the positive ion mode. The diagnostic characteristics of these compounds were obtained and the isomers could be successfully distinguished by comparison with their breakdown curves, even though the isomers differed only in the conformation of some groups of the isomer pairs. This report provides a rapid and reliable method for the identification of trace amounts of isomeric lignans by PESI-MS/MS. Furthermore, application of PESI and breakdown curves should have value in mass spectrometry studies of isomeric natural products compounds.

Three new oxazoline alkaloids from Gymnotheca chinensis

Abstract Three novel oxazoline alkaloids, 1-oxa-3-azaspiro [4.5] dec-2-ene-8-one (1), 1-oxa-3-azaspiro [4.5] dec-2, 6-diene-8-one (2), and 1-oxa-3-azaspiro [4.5] dec-10-methoxy-2, 6-diene-8-one (3) were isolated from the methanol extract of the whole plant of Gymnotheca chinensis. The chemical structures were established by means of spectroscopic analysis including one- and two-dimensional NMR spectroscopy.

Mahimbrine A, a Novel Isoquinoline Alkaloid Bearing a Benzotropolone Moiety from Mahonia imbricata

A novel isoquinoline alkaloid, mahimbrine A, possessing a rare benzotropolone framing scaffold, was isolated from the endemic plant of Mahonia imbricata. Its structure was established on the basis of extensive spectroscopic analysis. A plausible biosynthetic route of mahimbrine A was proposed. Mahimbrine A showed no antimicrobial activity at the concentration of 1 mg/mL.

Chemical Constituents of the Aerial Parts of Schnabelia oligophylla

A new triterpenoid derivative, 2,3-seco-bauer-8-en-2,3-dioic acid (1), a new natural product, 3α-hydroxyolean-13(18)-en-24-oic acid (2), along with 19 known compounds (3–21), were isolated from the methanol extract of the aerial parts of Schnabelia oligophylla. The chemical structures were established by means of spectroscopic analysis including one- and two-dimensional NMR spectroscopy and comparison with previously reported data.

Phytochemical Investigation of Gymnotheca chinensis

A new benzocycloheptanone derivative, named gymnothedelignan C, and 14 known compounds were isolated from the Chinese endemic genus plant Gymnotheca chinensis Decne. The structure of the new compound was established by 1D and 2D NMR experiments.

A new ursane-type triterpenoid saponin from the aerial parts of Clematoclethra scandens subsp. actinidioides.

A new ursane-type triterpenoid saponin, 2α,3α,24-trihydroxyurs-12,20(30)-dien-28-oic acid β-D-glucopyranosyl ester (1), together with six known triterpenoid saponins, was isolated and characterized from the aerial parts of Clematoclethra scandens subsp. actinidioides.