Jiaozhen Zhang

Pallambins A and B, Unprecedented Hexacyclic 19-nor-Secolabdane Diterpenoids from the Chinese Liverwort Pallavicinia ambigua

Pallambins A (1) and B (2), two novel 19-nor-7,8-secolabdane diterpenoids with unprecedented tetracyclo[4.4.0(3,5).0(2,8)]decane skeletons, along with a pair of structurally related isomers, pallambins C (3) and D (4), were isolated from the Chinese liverwort Pallavicinia ambigua. Their structures with absolute configurations were determined by means of NMR, X-ray diffraction, and CD analyses. Their preliminary cytotoxicity to human cancer cells was also tested.

Marsupellins A-F, ent-longipinane-type sesquiterpenoids from the Chinese liverwort Marsupella alpine with acetylcholinesterase inhibitory activity.

Acetylcholinesterase (AChE) inhibitory activity-guided fractionation of the Chinese liverwort Marsupella alpine afforded six new [marsupellins A-F (1-6)] and three known (7-9) ent-longipinane-type sesquiterpenoids. The structures were determined from MS and NMR spectroscopic data, single-crystal X-ray diffraction, and electronic circular dichroism calculations. Compounds 1-9 exhibited moderate to weak AChE inhibitory activity.

Highly Rigid Labdane-Type Diterpenoids from a Chinese Liverwort and Light-Driven Structure Diversification

Two unprecedented labdane-type diterpenoids haplomintrins A (1) and B (2) with six rings system were isolated from a Chinese liverwort Haplomitrium mnioides. Light-driven reaction of homologous haplomitrenonolides C (6), A (4), and D (3) afforded haplomintrins A-C (1, 2, and 7), respectively, while 4 was converted to more complex congeners haplomintrins D-G (8-11) through intramolecular cyclization. Formation of 1 and 2 from compounds 6 and 4, respectively, helps us to postulate that a photochemical reaction is involved in the biosynthetic pathway. These structure features can be used as molecular markers of H. mnioides, and their allelopathic effects are also preliminarily tested.

Hapmnioides A–C, Rearranged Labdane-Type Diterpenoids from the Chinese Liverwort Haplomitrium mnioides

Many exceptional labdane-type diterpenoids have been exclusively found in liverworts, which serve as taxonomic molecules or play important ecological roles in interactions among organisms. Three unprecedented labdane-type diterpenoids hapmnioides A (1), B (2), and C (3) formed through cascade rearrangement from the Chinese liverwort Haplomitrium mnioides are reported. Their structures were established by comprehensive spectroscopic analysis coupled with single-crystal X-ray diffraction, and their anti-inflammatory activities were also preliminarily tested.

Scapairrins A–Q, Labdane-Type Diterpenoids from the Chinese Liverwort Scapania irrigua and Their Cytotoxic Activity

Seventeen new labdane-type diterpenoids, scapairrins A-Q (1-17), including six pairs of diastereoisomers, and three known analogues (18-20) were isolated from the Chinese liverwort Scapania irrigua. The structures of 1-17 were determined based on a combination of the analysis of their MS and NMR spectroscopic data, single-crystal X-ray diffraction, and electronic circular dichroism calculations. Cytotoxicity testing showed that compounds 7-10 exhibited inhibitory activities against a small panel of human cancer cell lines.

Interconversion of the Pallambins through Photoinduced Rearrangement

A new photoinduced interconversion of four naturally occurring 19-nor-7,8-secolabdane diterpenoids was discovered and analyzed. The photochemical mechanism, intramolecular diradical rearrangement reaction, was investigated by time-lapse monitoring of the end product formations with HPLC and UV, as well as detailed theoretical calculations.

Heptaketides from an Endolichenic Fungus Biatriospora sp. and Their Antifungal Activity

Twelve new heptaketides, biatriosporins A-L (1-12), biatriosporin M (13) (a ramulosin derivative), and 19 known compounds (14-32) were isolated from the endolichenic fungus Biatriospora sp. (8331C). The structures of these compounds were determined by analyzing MS and NMR data. The absolute configurations of compounds 1, 2, 7, and 9 were determined by single-crystal X-ray diffraction analysis, whereas compound 10 was deduced with Moshers method. Four of the compounds were active in an antifungal assay. The most potent compound, compound 4, also sensitized clinically derived azole-resistant Candida albicans strains to fluconazole (FLC). A mechanistic investigation revealed that 4 inhibited the function of efflux pumps and reduced the transcriptional expression of the efflux-pump-related genes CDR1 and CDR2.

cis-clerodane diterpenes from the liverwort Scapania ciliata.

Chemical investigation of the Chinese liverwort Scapania ciliata led to the isolation of four new cis‐clerodane lactones, named ciliatolides A–D (1–4, resp.), among which compound 1 was found to be a tetranorclerodanoid. Their structures were determined by extensive analysis of spectroscopic data, and, in the case of compound 1, together with a single‐crystal X‐ray diffraction analysis. The absolute configurations were established by analysis of the CD spectra and by quantum‐chemical CD calculations. The cytotoxicities of compounds 1–4 were preliminarily tested against the PC3 and MCF‐7 cell lines.

Bibenzyl-Based Meroterpenoid Enantiomers from the Chinese Liverwort Radula sumatrana

Six new pairs of bibenzyl-based meroterpenoid enantiomers, (±)-rasumatranin A-D (1-4) and (±)-radulanin M and N (5 and 6), and six known compounds were isolated from the adnascent Chinese liverwort, Radula sumatrana. Their structures were elucidated based on spectroscopic data and chiral phase HPLC-ECD analyses. The structures of 1 and 7 were also confirmed by single-crystal X-ray diffraction analysis. Cytotoxicity tests of the isolated compounds showed that 6-hydroxy-3-methyl-8-phenylethylbenzo[b]oxepin-5-one (8) showed activity against the human cancer cell lines MCF-7, PC-3, and SMMC-7721, with IC50 values of 3.86, 6.60, and 3.58 μM, respectively, and induced MCF-7 cell death through a mitochondria-mediated apoptosis pathway.

Four New Kaurane Diterpenoids from the Chinese Liverwort Jungermannia comata Nees.

In our continuing program to find new bioactive compounds from the Chinese liverworts, four new kaurane‐type diterpenoids, (6β)‐kaur‐16‐ene‐6,9‐diol (1), (6β,12β)‐kaur‐16‐ene‐6,9,12‐triol (2), (6β)‐kaur‐16‐ene‐5,6,9‐triol (3), and kaur‐16‐ene‐9,19‐diol (4), have been isolated from the Chinese liverwort Jungermannia comata Nees. Five known kaurane‐type diterpenoids (5 – 9) and four known trachylobane‐type diterpenoids (10 – 13) were also obtained. The structures of the new compounds were established unequivocally on the basis of spectroscopic data. The absolute configuration of compound 1 was established by comparing experimental and calculated electronic circular dichroism spectra.