Jun-Hua Zheng

Comparison of phenolic compounds of rhubarbs in the section deserticola with Rheum palmatum by HPLC-DAD-ESI-MSn.

A sophisticated LC-ESI-MS (n) method was utilized for the analysis of the phenolic compounds in five unofficial RHEUM species for the first time. These species belong to the section deserticola Maxim. of the Polygonaceae family, including Rheum racemiferum Maxim., R. nanum Siev. ex Pall., R. delavayi Franch., R. sublanceolatum C. Y. Cheng et T. C. Kao and R. pumilum Maxim. A total of 101 phenolic compounds, including sennosides, anthraquinones, stilbenes, glucose gallates, naphthalenes, procyanidins and chromones were identified or tentatively characterized based on their UV and mass spectral data from the methanol extracts. These chemical constituents were compared with those of an official species ( R. palmatum l.). The results showed that most sennosides and procyanidin derivatives were only present in R. palmatum rather than in the unofficial species; stilbenes and chromones were only found in the sect. deserticola species; while anthraquinones, glucose gallates and naphthalenes could be detected in all studied species. For anthraquinone glycosides, only emodin O-glucosides were detected in the sect. deserticola species. Moreover, remarkable difference was observed among unofficial species. These results may be useful for the quality control of rhubarb in order to guarantee its clinical effects, and may also be helpful for the further clarification of the taxonomic relationship of the plants in the sect. deserticola.

Biotransformation of 4(20),11-taxadienes by cell suspension cultures of Platycodon grandiflorum

Platycodon grandiflorum cell suspension cultures were employed to biotransform the taxane diterpenoids 2 f ,5 f , 10 g ,14 g -tetraacetoxy-4(20),11-taxadiene ( 1 ) and 9 f -hydroxy-2 f , 5 f ,10 g ,14 g -tetraacetoxy-4(20),11-taxadiene ( 2 ). One product, 10 g -hydroxy-2 f ,5 f ,14 g -triacetoxy-4(20),11-taxadiene ( 3 ) was obtained from 1 and two products, 9 f ,10 g -dihydroxy-2 f ,5 f ,14 g -triacetoxy-4(20),11-taxadiene ( 4 ) and 10 g -hydroxy-2 f ,5 f ,9 f ,14 g -tetraacetoxy-4(20),11-taxadiene ( 5 ) were obtained from 2 incubated with Platycodon cultured cells respectively, among which 5 is characterized as a new taxoid compound. The effects of the addition stage for 1 and 2 on the biotransformation were investigated and the results revealed that: (1) the optimal addition stage for 1 was in the early logarithmic phase (6th day) of the cell growth period, in which 78% of 1 was converted and the yield for 3 reached 75%; (2) the optimal addition stage for 2 was on the mid-logarithmic phase (12th day) of the cell growth period, in which 25.3% of 2 was converted and the yields for 4 and 5 reached 18.9 and 14.5%, respectively.

A Triterpenod Saponin from Albizia Julibrissin

A triterpenoid saponin (1) was obtained from the stem barks of Albizia julibrissin Durazz. Its structure was elucidated 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-beta-D-quinovopyranosyl-2, 7-octadienoyl]-16-deoxy-acacic acid 28-O-beta-D-glucopyranosyl-(1 --> 3)-[alpha-L-arabinofuranosyl-(1 --> 4)]-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl ester (1), named as Julibroside J26, based on the chemical and spectral methods.

Substrate specificity for the hydroxylation of polyoxygenated 4(20),11-taxadienes by Ginkgo cell suspension cultures

Three C-14 oxygenated taxanes isolated from callus cultures of Taxus spp., 2alpha,5alpha,10beta,14beta-tetra-acetoxy-4(20),11-taxadiene 3, 2alpha,5alpha,10beta-triacetoxy-14beta-propionyloxy-4(20),11-taxadiene 4, 2alpha,5alpha,10beta-triacetoxy-14beta-(2-methylbutyryl)-oxy-4(20),11-taxadiene 5, and three deacetylated derivatives of 3, 10beta-hydroxy-2alpha,5alpha,14beta-triacetoxy-4(20),11-taxadiene 6, 14beta-hydroxy-2alpha,5alpha,10beta-triacetoxy-4(20),11-taxadiene 7, 10beta,14beta-dihydroxy-2alpha,5alpha-diacetoxy-4(20),11-taxadiene 8, could all be regio- and stereo-selectively hydroxylated at the 9alpha-position by Ginkgo cell suspension cultures to yield a series of new 9alpha,14beta-dihydroxylated taxoids. The effects of functional groups, especially at C-14 of the substrates, on the biotransformation were also investigated. The results revealed that substrates with an acetoxyl group at C-14 could be more efficiently 9alpha-hydroxylated than those with a longer ester chain or a hydroxyl group at C-14. An acetoxyl or hydroxyl group at C-10 had no effect on the conversion rates of the substrates, but substrates with the hydroxyl group (compared with the acetoxyl analogues) could be converted into 9alpha-hydroxylated products more easily.

A New Isomer of Julibroside J2 from Albizia julibrissin

Abstract A new isomer of Julibroside J2 (Chen, S.P., Zhang, R.Y., Ma, L.B. and Tu, G.Z. Acta Pharm. Sinica, 1997, 32, 110–115) was obtained from the cytotoxic fraction of 95% ethanol extracts of stem barks of Albizia julibrissin Durazz, together with Julibroside J2. Its structure was elucidated as 3-O-[β-D-xylopyranosyl-(1 → 2)-α-L-arabinopyranosyl-(1 → 6)-β-D-glucopyranosyl]-21-O-{(6S)-2-trans-2-hydroxymethyl-6-methyl-6-O-[3-O-((6S)-2-trans-2-hydroxymethyl-6-methyl-6-hydroxy-2,7 -octadienoyl)-β-D-quinovopyranosyl]-2,7-octadienoyl} acacic acid 28-O-β-D-glucopyranosyl-(1 → 3)-[α-L-arabinofuranosyl-(1 → 4)]-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranosyl ester(1), named as Julibroside J7, based on chemical and spectral methods. Julibroside J2 showed good inhibitory action against KB cell line in vitro.

A New Phenolic Glycoside and a New Trans-clerodane Diterpene from Conyza Blinii

Abstract A new phenolic glycoside, 4-propionyl-2,6-dimethoxyphenyl β-D-glucopyranoside (1) and a new trans-clerodane diterpene named 19-deacetylconyzalactone (2), were isolated from the aerial parts of Conyza blinii.

Two new constituents from Rheum sublanceolatum.

The chemical investigation of Rheum sublanceolatum has led to the isolation of two new constituents, the structures of which were identified on the basis of physical and spectroscopic analysis as 2-acetyl-3-methyl-6,8-dihydroxy-2,3,4,4-tetrahydronaphthalene-1-one-6-O-β-d-glucopyranoside (1) and 2,5-dimethyl-7-hydroxychromone-7-O-β-d-(6′-O-galloyl)-glucopyranoside (2).

Callus cultures of Annona squamosa for the production of annonaceous acetogenins

Callus cultures of Annona squamosa were induced using different explants including petals, seed contents (megagametophyte and embryo) and fruits (mesocarp). Growth of the calli induced from the explants was found to be influenced by the type, concentration and ratio of auxin vs. cytokinin. The content of squamocin (67.8 w g g m 1 dry weight) in calli cultured on Gamborg B-5 medium containing 5.0 mg l m 1 naphthalene acetic acid and 4.0 mg l m 1 zeatin was nearly seven times higher than that in intact fruits.

Biotransformation of 24α-Methylcholesterol and 24β-Methylcholesterol by Yeast Mutant GL7

Abstract Incubation of 24α- and 24β-methylcholesterols with yeast mutant GL7 afforded their corresponding C-22-desaturated products under the catalysis of sterol Δ22(23)-desaturase. The metabolites were identified to be 22-dehydro-24α-methylcholesterol (2% yield from 24α-methylcholesterol) and 22-dehydro-24β-methylcholesterol (51% yield from 24β-methylcholesterol) respectively on the basis of their chromatographic and spectral properties. It was concluded that the sterol Δ22(23)-desaturase prefers the 24β-methyl sterols and is highly stereospecific.