Jianhua Zou

Periconiasins A–C, New Cytotoxic Cytochalasans with an Unprecedented 9/6/5 Tricyclic Ring System from Endophytic Fungus Periconia sp.

Periconiasins A-C (1-3), new cytochalasans with an unprecedented 9/6/5 tricyclic ring system, were isolated from the endophytic fungus Periconia sp. F-31. Their structures and absolute configurations were elucidated by extensive spectroscopic and X-ray crystallographic analyses. Their biosynthesis is proposed to occur from an unusual seven acetate/malonate polyketide backbone attached to one leucine moiety by a PKS-NRPS followed by Diels-Alder and other reactions. 1 and 2 showed significant cytotoxicity against human HCT-8 cancer cells.

Periconianone A, a new 6/6/6 carbocyclic sesquiterpenoid from endophytic fungus Periconia sp. with neural anti-inflammatory activity.

Periconianone A (1), a polyoxygenated sesquiterpenoid with a new 6/6/6 tricarbocyclic skeleton, and periconianone B (2) were isolated from the endophytic fungus Periconia sp. Their structures and absolute configurations were elucidated by extensive spectroscopic analyses, calculated ECD, and single-crystal X-ray diffraction (Cu Kα). The biosynthesis of the unusual six-membered carbonic ring of 1 was postulated to be formed through intramolecular aldol condensation. Compounds 1 and 2 showed significant neural anti-inflammatory activity.

Molecular Characterization and Phylogenetic Analysis of Two Novel Regio-specific Flavonoid Prenyltransferases from Morus alba and Cudrania tricuspidata

Background: Plant flavonoid prenyltransferases (FPTs) transfer prenyl moiety to flavonoid cores and have previously been identified only in Leguminosae. Results: The newly identified moraceous FPTs, MaIDT, and CtIDT, are distantly related to leguminous FPTs and feature catalytic regioselectivity and promiscuity. Conclusion: MaIDT and CtIDT evolved independently from leguminous FPTs. Significance: These findings are valuable for identifying additional evolutionarily different non-Leguminosae FPTs. Prenylated flavonoids are attractive specialized metabolites with a wide range of biological activities and are distributed in several plant families. The prenylation catalyzed by prenyltransferases represents a Friedel-Crafts alkylation of the flavonoid skeleton in the biosynthesis of natural prenylated flavonoids and contributes to the structural diversity and biological activities of these compounds. To date, all identified plant flavonoid prenyltransferases (FPTs) have been identified in Leguminosae. In the present study two new FPTs, Morus alba isoliquiritigenin 3′-dimethylallyltransferase (MaIDT) and Cudrania tricuspidata isoliquiritigenin 3′-dimethylallyltransferase (CtIDT), were identified from moraceous plants M. alba and C. tricuspidata, respectively. MaIDT and CtIDT shared low levels of homology with the leguminous FPTs. MaIDT and CtIDT are predicted to be membrane-bound proteins with predicted transit peptides, seven transmembrane regions, and conserved functional domains that are similar to other homogentisate prenyltransferases. Recombinant MaIDT and CtIDT were able to regioselectively introduce dimethylallyl diphosphate into the A ring of three flavonoids with different skeleton types (chalcones, isoflavones, and flavones). Phylogenetic analysis revealed that MaIDT and CtIDT are distantly related to their homologs in Leguminosae, which suggests that FPTs in Moraceae and Leguminosae might have evolved independently. MaIDT and CtIDT represent the first two non-Leguminosae FPTs to be identified in plants and could thus lead to the identification of additional evolutionarily varied FPTs in other non-Leguminosae plants and could elucidate the biosyntheses of prenylated flavonoids in various plants. Furthermore, MaIDT and CtIDT might be used for regiospecific prenylation of flavonoids to produce bioactive compounds for potential therapeutic applications due to their high efficiency and catalytic promiscuity.

GuA6DT, a Regiospecific Prenyltransferase from Glycyrrhiza uralensis, Catalyzes the 6-Prenylation of Flavones

GuA6DT, a flavonoid prenyltransferase, was identified from Glycyrrhiza uralensis, and it was found that this enzyme regiospecifically transfers a dimethylallyl moiety to apigenin at the C‐6 position. A further substrate specificity investigation indicated that the existence of hydroxyls at both the C‐5 and C‐7 positions of the flavone skeleton is critical for the prenylation. However, substitutions on the B‐ring had negligible influence on the prenylation. A comparison of GuA6DT expression in different organs revealed that mRNA is mainly expressed in the aerial parts. Moreover, the GuA6DT mRNA was found to be regulated at the transcriptional level, because methyl jasmonate induced upregulation in cultured cells. GuA6DT is the first identified flavone prenyltransferase to exhibit strict substrate specificity and regiospecificity.

Qualitative and quantitative analysis of phenylpropanoids in cell culture, regenerated plantlets and herbs of Saussurea involucrata.

The major phenylpropanoids in the cell culture, regenerated plantlets and herbs of Saussurea involucrata were systematically and comparatively investigated. A total of 17 constituents were identified on the basis of HPLC-DAD/ESI-MS(n) and HPLC-ESI-IT-TOF/MS analyses. Among them, 13 constituents were unambiguously identified by comparing the retention time, UV, MS and MS(n) spectra of samples with standards/literature, and the other 4 constituents were tentatively assigned on the basis of their UV spectra and MS(n) fragmentation patterns. In addition, a quantification method for the simultaneous quantification of 3 major phenylpropanoids syringin, 5-caffeoylquinic acid, and 1,5-dicaffeoylquinic acid was successfully established. The established HPLC quantification method was proved to have excellent linearity, precision, repeatability and accuracy. These studies provide a secondary metabolic profile of the cell cultures of S. involucrata, which is valuable for improving the quality control of cell culture and sheds light on the biosynthetic pathway of phenylpropanoids in this species.

A furantaxane with an unusual 6/8/6/5 ring system and potent tumor MDR reversal activity obtained via microbial transformation.

A furantaxane (4) with an unusual 6/8/6/5 ring system and two hydroxylated products (2, 3) were isolated following the biotransformation of a taxane (1) by Streptomyces griseus. The structures of the isolates were elucidated by spectroscopic analysis. The absolute configuration of 4, which exhibited potent reversal activity in the A549/taxol MDR tumor cell line, was unambiguously deduced by single-crystal X-ray diffraction.

Chemical constituents from the cell cultures of Saussurea involucrata

The chemical constituents of the cell cultures of Saussurea involucrata were systematically investigated, thus a new eudesmane-type sesquiterpene together with 14 known compounds was isolated. Among them, syringin is the main compound with an isolated yield of 0.3%. The new compound was characterized as 11βH-2α-hydroxy-eudesman-4(15)-en-12,8β-olide (1) on the basis of extensive spectroscopic data.

Neolignans and Sesquiterpenes from Cell Cultures of Stellera chamaejasme

Two new neolignans (1, 2) and six sesquiterpenes (3- 8) were isolated from the cell cultures of Stellera chamaejasme. Their structures and absolute configurations were elucidated by extensive spectroscopic and computational methods. Compound 4 exhibited significant protective effects against CCl (4)-induced hepatotoxicity in HepG2 cells, reducing aspartate aminotransferase release by 29.49 % at 10 µM. These compounds have not been isolated from plant material, which implies that in vitro plant cell cultures may offer alternative and effective sources of bioactive natural compounds.

Microbial transformation of ginsenoside-Rg1 by Absidia coerulea and the reversal activity of the metabolites towards multi-drug resistant tumor cells

Biotransformation of ginsenoside-Rg₁ (1) by the fungus Absidia coerulea AS 3.2462 yielded five metabolites (2-6). On the basis of spectroscopic data analyses, the metabolites were identified as ginsenoside-F₁ (2), 6α,12β-dihydroxydammar-3-one-20(S)-O-β-D-glucopyranoside (3), 3-oxo-20(S)-protopanaxatriol (4), 3-oxo-7β-hydroxy-20(S)-protopanaxatriol (5), and 3-oxo-7β,15α-dihydroxy-20(S)-protopanaxatriol (6), respectively. Among them, 5 and 6 are new compounds. These results indicated that Absidia coerulea AS 3.2462 could catalyze the specific C-3 dehydrogenation of derivatives of ginsenoside-Rg₁, as well as hydroxylation at the 7β and 15α positions. Metabolites 2, 4 and 5 exhibited moderate reversal activity towards A549/taxol MDR tumor cells in vitro.

A new labdane type diterpenoid from Trollius ledebouri.

A new labdane type diterpenoid, (8α,13R)-epoxy-14-labden-6β,7β-diol-7-β-D-(4′-acetyl) fucopyranoside, named ledebourene 1, was isolated from the flowers of Trollius ledebouri. The absolute stereostructure was elucidated on the basis of the spectroscopic analysis.