Shi-Fei Li

Three New Indole Alkaloids from Trigonostemon lii

Three unprecedented indole alkaloids, trigonoliimines A-C (1-3) with a unique polycyclic system, were isolated from the leaves of Trigonostemon lii Y. T. Chang. The structures of 1-3 were determined by the spectroscopic, computational, and CD exciton chirality approaches. Trigonoliimine A showed modest anti-HIV-1 activity (EC(50) = 0.95 microg/mL, TI = 7.9).

Indole alkaloids from Ervatamia chinensis

Four vobasinyl-ibogan type bisindole alkaloids, ervachinines A-D (1-4), along with 12 known terpenoid indole alkaloids, were isolated from the whole plant of Ervatamia chinensis. Their structures were elucidated by analysis of spectroscopic data, including 1D and 2D NMR, and the absolute configurations of 1-4 were determined by CD exciton chirality method. All of the compounds were evaluated for in vitro cytotoxicity against five human cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7 and SW480. Bisindole alkaloids 1-6 exhibited inhibitory effects, with IC(50) values comparable to those of cisplatin.

Trigonosins A-F, daphnane diterpenoids from Trigonostemon thyrsoideum.

Phytochemical study of the roots of Trigonostemon thyrsoideum led to the isolation of four new oxygenated daphnane-type diterpenoids, trigonosins A-D (1-4), and two new modified daphnanes, trigonosins E and F (5 and 6). The structures and relative configurations were elucidated on the basis of extensive spectroscopic analysis, including 1D and 2D NMR experiments. All compounds isolated were evaluated for their cytotoxicity against HL-60, A549, and MCF-7 human cancer cell lines.

β-Carboline alkaloids from the leaves of Trigonostemon lii Y.T. Chang.

A phytochemical work on the alkaloid constituents from Trigonostemon lii Y.T. Chang was conducted to give six new β-carboline alkaloids, trigonostemines A-F (1-6) and eight known β-carboline alkaloids (7-14). Their structures were elucidated by extensive spectroscopic techniques including 2D NMR experiments and mass spectrometry. All of the compounds were evaluated for their cytotoxic activities against the HL-60, SMMC-7721, A-549, MCF-7, and SW480 human cancer cell lines. Trigonostemines A and B (1 and 2) exhibited stronger inhibitory activities than the positive control (cisplatin) in some cell lines.

Three new terpenoid indole alkaloids from Catharanthus roseus.

Three new terpenoid indole alkaloids, vidolicine (1), normacusine B N-oxide (2), and lochnerine N-oxide (3), together with seven known ones (4-10), were isolated from whole plants of Catharanthus roseus. Their structures were elucidated by spectroscopic methods (NMR, MS, UV, and IR). Cytotoxic activities of these isolates (1-10) were evaluated, but only compound 8 was active against HL-60, SMMC-7721, and A549 cell lines.

Cytotoxic Limonoids from Melia azedarach

Five new compounds (1-5), including two limonoids, one triterpenoid, one steroid, and one sesquiterpenoid, along with nine known limonoids (6-14), were isolated from the bark of Melia azedarach. The structures of the new compounds were elucidated by 2D NMR spectroscopy and mass spectrometry. The isolated compounds as well as three acetylated derivatives of 9 were evaluated for their cytotoxicities against five human tumor cell lines (HL-60, SMMC-7721, A-549, MCF-7, and SW480) by an MTT assay. Seven limonoids (1, 6, 7, 8, 9, 9b, and 9c) showed significant inhibitory activities against tested cell lines with IC50 values ranging from 0.003 to 0.555 µM, and their preliminary structure-activity relationships are also discussed.

Eudesmanolides from Wedelia trilobata (L.) Hitchc. as Potential Inducers of Plant Systemic Acquired Resistance

Ten eudesmanolides (1-10) including five new ones (1-4 and 6) were isolated from the whole plant of Wedelia trilobata (L.) Hitchc., a notoriously invasive weed in South China. As main constituents of W. trilobata, eight of these eudesmanolides were tested for their antitobacco mosaic virus (TMV) activities by the conventional half-leaf and leaf-disk method along with Western blot analysis. All of the tested compounds, at 10 μg/mL, showed strong antiviral activities in the pretreated tobacco plants with inhibition rates ranging from 46.7% to 76.5%, significantly higher than that of the positive control, ningnanmycin (13.5%). Their potential of inducing systemic acquired resistance (SAR) was also evaluated, and compounds 1 and 8 showed excellent induction activities. Furthermore, it was found that different concentrations of compound 1 promoted phenylalanine ammonia-lyase (PAL) activity in tobacco plants. To our knowledge, this is the first report that eudesmanolides could induce resistance in tobacco plants against the viral pathogen TMV.

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.

Daphnane diterpenoids from the stems of Trigonostemon lii and their anti-HIV-1 activity

Thirteen highly oxygenated daphnane diterpenoids, including six known compounds, were isolated from the stems of Trigonostemon lii. The structures were elucidated by extensive spectroscopic analyses including 2D NMR spectroscopy (HSQC, (1)H-(1)H COSY, HMBC, and ROESY) and mass spectrometry. The absolute stereochemistries of compounds were established on the basis of CD spectra. Four of the compounds showed modest anti-HIV-1 activity (EC50=2.04, 9.17, 11.42, and 9.05 μg/ml, TI=26.49, >21.81, 9.32, and 9.56, respectively) in vitro.

Cytotoxic eburnamine-aspidospermine type bisindole alkaloids from Bousigonia mekongensis

Four new eburnamine-aspidospermine type bisindole alkaloids, namely, mekongenines C-F (1-4), along with 27 known indole alkaloids were isolated from the twigs and leaves of Bousigonia mekongensis. Their structures with the absolute configurations were elucidated by spectroscopic methods and ECD analyses. All new compounds were evaluated for their cytotoxicities against five human cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7 and SW480 in vitro. Alkaloids 1-4 exhibited inhibitory effects with IC50 values comparable to those of cisplatin.