Rensheng Xu

Antifungal alkaloids and limonoid derivatives from Dictamnus dasycarpus

From the root bark of Dictamnus dasycarpus (Rutaceae), four limonoid derivatives, two furoquinoline alkaloids, five limonoids, two sesquiterpenes and three steroids were isolated and their structures elucidated on the basis of various spectroscopic methods. Among the identified compounds, one was determined to be a new natural product, 6 beta-hydroxyfraxinellone, while six compounds were found to be active against the plant pathogenic fungus Cladosporium cucumerinum. The relationship between the structures of limonoid derivatives and their inhibitory activity against fungal growth was investigated.

Casbane diterpenoids from Euphorbia ebracteolata

Abstract From the ethanol extract of the roots Euphorbia ebracteolata, two new casbane diterpenoids, named yuexiandajisu A and B, were isolated. Their structures were elucidated by spectral analyses including 1H-1H COSY, 13C-1H COSY, COLOC and NOESY and confirmed by X-ray crystallography. In vitro bioassays showed that yuexiandajisu A exhibited antibacterial activity and yuexiandajisu B inhibited proliferation of B lymphocytes.

Triterpenoid saponins from Clematis chinensis

From the roots of Clematis chinensis, two new triterpenoid saponins, named clematichinenoside A and B, were isolated and their structures were elucidated as 3-O-beta-D-ribopyranosyl-(1-3)-alpha-L-rhamnopyranosyl-(1-2)-alpha -L- arabinopyranosyl oleanolic acid 28-O-beta-D-glucopyranosyl ester and 3-O-beta-D-glucopyranosyl-(1-4)-beta-D-ribopyranosyl-(1-3)-alpha-L - rhamnopyranosyl-(1-2)-alpha-L-arabinopyranosyl hederagenin 28-O-alpha-L-rhamnopyranosyl-(1-4)-beta-D-glucopyranosyl-(1-6)- beta-D-glucopyranosyl ester, respectively. In addition oleanolic acid, hederagenin and seven known saponins were obtained.

Saponins from Clematis chinensis

From ethanol extracts of the roots of Clematis chinensis, a new saponin, named clematichinenoside C, was isolated and its structure was established as 3-O-beta-D-glucopyranosyl-(1-4)-beta-D-ribopyranosyl-(1-3)-alpha-L - rhamnopyranosyl-(1-2)-alpha-L-arabinopyranosyl oleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1-4)-beta-D-glucopyranosyl- (1-6)-beta-D-glucopyranosyl ester by spectroscopic and chemical means. In addition, one known saponin, huzhongoside B, was identified in the plant.

Alkaloids from Stemona tuberosa

Abstract Two new alkaloids, neotuberostemonine and bisdehydroneotuberostemonine were isolated from the roots of Stemona tuberosa , collected in Yunnan Province. Their structures were elucidated by various spectral methods.

Bibenzyls from Stemona tuberosa.

Three new bibenzyls were isolated from the roots of Stemona tuberosa. Their structures were identified by spectroscopic methods as 3,5-dihydroxy-4-methylbibenzyl, 3,5-dihydroxy-2-methoxy-4-methylbibenzyl and 3-hydroxy-2,5-dimethoxy-2-methylbibenzyl.

Triterpenes and triterpenoid saponins from Mussaenda pubescens

Two novel triterpenoid saponins, named mussaendosides U and V, together with one known saponin and four known triterpenes were isolated from the aerial parts of Mussaenda pubescens (Rubiaceae). The structures were determined on the basis of chemical analysis ad spectral methods. All these compounds were identified for the first time from the genus Mussaenda.

Sesquiterpene glycosides from Dictamnus dasycarpus

Five novel sesquiterpene glycosides named dictamnosides A-E were isolated from the methanol extract of the root bark of Dictamnus dasycarpus. Their structures were established on the basis of X-ray diffraction, spectroscopic and chemical methods.

An Isopimarane Diterpene from Euphorbia Ebracteolata Hayata

Abstract From the ethanolic extract of the roots of Euphorbia ebracteolata Hayata four compounds were isolated. They are 24-methylenecycloartanone, tirucallol, procesterol and a new isopimarane diterpene, namely yuexiandajisu C. The structure of yuexiandajisu C was elucidated by spectral analysis. The bioassay in vitro showed yuexiandajisu C exhibited immunomodulatory activity.

Saponins from Mussaenda pubescens

Two new triterpenoid saponins, named mussaendosides G and K, were isolated from aerial parts of Mussaenda pubescens by normal and reverse phase chromatography. On the basis of chemical and spectroscopic methods, their structures have been elucidated as heinsiagenin A 3-O-{alpha-L-rhamnopyranosyl(1-->2)-[beta-D-glucopyranosyl (1-->6)]-beta-D-glucopyranosyl(1-->2)}-alpha-L -rhamnopyranosyl(1-->4)-O-beta-D-glucopyranoside and 3 beta,19 alpha-dihydroxyl-olean-12-en-24, 28-dioic acid-24,28-di-O-beta-D-glucopyranoside, respectively.