Yu-Cheng Gu

Trigohowilols A−G, Degraded Diterpenoids from the Stems of Trigonostemon howii

Two new degraded diterpenoids, trigohowilols A (1) and B (2), four new heterodimers, trigohowilols C-F (3-6), one new homodimer, trigohowilol G (7), and three known degraded diterpenoids (8-10) were isolated from the methanol extract of the stems of Trigonostemon howii. Compounds 1-7 were evaluated for their cytotoxic activity against five human tumor cell lines by an MTT assay, and trigohowilols E (5) and F (6) exhibited inhibitory activity with IC50 values ranging from 2.33 to 12.57 μM. Moreover, compounds 1-6 showed weak antimicrobial activities (MIC values: 6.25-25 μg/mL) against Staphylococcus aureus, Pseudomonas aeruginosa, MRSA 92(#), and MRSA 98(#) using a 2-fold dilution method.

Myrifabine, the First Dimeric Myrioneuron Alkaloid from Myrioneuron faberi

One Myrioneuron alkaloid, myrifabine (1), the first example of a dimer with 12 chiral centers embraced in a decacyclic novel skeleton, was isolated from Myrioneuron faberi . Its structure was elucidated by spectroscopic data and single-crystal X-ray diffraction. The antimicrobial and cytotoxic activities of 1 were evaluated in vitro.

Stereochemical determination of new cytochalasans from the plant endophytic fungus Trichoderma gamsii

Three new cytochalasans, trichalasins E (1), F (2) and H (7), together with four known analogues, trichalasin C (3), aspochalasin K (4), trichalasin G (5) and aspergillin PZ (8), were isolated from one endophytic fungus Trichoderma gamsii inhabiting in the traditional medicinal plant Panax notoginseng (BurK.) F.H. Chen. Trichalasins E (1) contains a unique hydroperoxyl group, which is the first report in all known analogues, whereas trichalasin H (7) possesses the rare 6/5/6/6/5 pentacyclic skeleton with 12-oxatricyclo [6.3.1.0(2,7)] moiety as that of aspergillin PZ (8). The relative configurations of the new compounds were characterized by analysis of coupling constants and ROESY correlations, and the absolute configurations of trichalasins E (1), H (7) and aspergillin PZ (8) were determined by modified Moshers reaction. In addition, compounds 1-5, 7 and 8 were tested cytotoxic activities against several cancer cell lines.

Cyclohexane-Fused Octahydroquinolizine Alkaloids from Myrioneuron faberi with Activity against Hepatitis C Virus

Investigation of the alkaloids from Myrioneuron faberi, a plant unique to China, gave four pairs of enantiomers (1-4). (±)-β-Myrifabral A (1) and (±)-α-myrifabral A (2) formed an inseparable mixture of anomers (cluster A), as did (±)-β-myrifabral B (3) and (±)-α-myrifabral B (4) (cluster B). Their structures were determined by X-ray diffraction and NMR analysis. Compounds 1-4 possessed novel cyclohexane-fused octahydroquinolizine skeletons and represent the first quinolizidine alkaloids from the genus Myrioneuron. The epimers of cluster A (1 and 2) were modified and separated. In vitro, clusters A and B and their derivatives inhibited replication of hepatitis C virus (HCV, IC50 0.9 to 4.7 μM) with cytotoxicity lower than that of telaprevir.

9′-Epi-3β,3′β-dimethylxestospongin C, a new macrocyclic diamine alkaloid from the Hainan sponge Neopetrosia exigua

A new BIS-1-oxaquinolizidine alkaloid, 9- EPI-3 β,3 β-dimethylxestospongin C (2), and three known related analogues have been isolated from the Hainan sponge Neopetrosia exigua.

Apotirucallane protolimonoids from the Chinese mangrove Xylocarpus granatum Koenig.

A series of previously unreported compounds including seven new apotirucallane protolimonoids, xylogranatumines A-G (1-7), were isolated together with three known analogues (8-10) from the twigs and leaves of the Chinese mangrove, Xylocarpus granatum. The structures of these new compounds were elucidated by extensive spectroscopic analysis including 1D and 2D NMR and high-resolution electrospray ionization mass spectrometry (HRESIMS) and by comparison with those of related known compounds in the literature. Xylogranatumine F (6) exhibited cytotoxic activity against A549 tumor cell in vitro.

Daphmacrodins A and B, alkaloids from Daphniphyllum macropodum

Two new daphnicyclidin-type Daphniphyllum alkaloids, daphmacrodins A and B (1 and 2) were isolated from the leaves and stems of Daphniphyllum macropodum. Their structures were elucidated by extensive spectroscopic techniques, including 2D NMR spectroscopy and mass spectrometry. The relative configuration of 1 was further confirmed by a single-crystal X-ray diffraction analysis. Their cytotoxic activities against five human cancer cell lines, pesticidal activities against brine shrimp (Artemia salina), and antibacterial activities against five standard bacterial and fungal strains were evaluated. The structure of 1 was successfully transformed to 2 by a chemical method.Graphical abstract

Daphmacromines K-O, alkaloids from Daphniphyllum macropodum.

Five new yuzurimine-type Daphniphyllum alkaloids, daphmacromines K-O (1-5), were isolated from the leaves and stems of Daphniphyllum macropodum. Their structures were elucidated by extensive spectroscopic techniques, including 2D NMR spectroscopy and mass spectrometry. Daphmacromine O (5) showed moderate cytotoxic activity against brine shrimp.

Four new tetracyclic alkaloids with cis-decahydroquinoline motif from Myrioneuron effusum.

Four new Myrioneuron alkaloids, mysumamides A-D (1-4), along with three known ones were isolated from the twigs and leaves of Myrioneuron effusum. All of these alkaloids possessed the tetracyclic skeleton and contained the decahydroquinoline (cis-DHQ) moiety. Their structures and relative configurations were elucidated on the basis of spectroscopic methods, especially 2D NMR techniques. The absolute configuration of 1 was determined by single-crystal X-ray diffraction. The cytotoxic activities of these compounds were also evaluated in vitro.

Trichoderamides A and B, a pair of stereoisomers from the plant endophytic fungus Trichoderma gamsii

Trichoderamides A and B, a pair of stereoisomers from the plant endophytic fungus Trichoderma gamsii