Robustadial A and B from Eucalyptus globulus Labill. and their anticancer activity as selective tyrosyl-DNA phosphodiesterase 2 inhibitors.

Tyrosyl-DNA phosphodiesterase 2 (TDP2) is a recently discovered DNA repair enzyme that can repair topoisomerase 2-mediated DNA damage, resulting in cancer cell resistance. In this study, two compounds, robustadial A and B, were isolated from a fraction of the ethyl acetate extract of Eucalyptus globulus Labill. fruits based on TDP2 inhibition screening. The biological experiments indicated that robustadial A and B have TDP2 inhibitory activity with EC50 values of 17 and 42 µM, respectively, but no tyrosyl-DNA phosphodiesterase 1 inhibition at 100 µM. Robustadial A showed significant synergistic effects with the anticancer drug etoposide in four human cancer cell lines, non-small cell lung cancer cell line (A549), prostate cancer cell line (DU145), breast cancer cell line (MCF-7), colorectal adenocarcinoma cell line (HCT-116), and chicken lymphoma cell line (DT40), and chicken lymphoma cell line complementation with human TDP2 (DT40 hTDP2) with combination index values ranging from 0.21 to 0.74. This work will facilitate future efforts for the development of robustadial A-based TDP2 selective inhibitors.

Sesquiterpenoids from the aerial parts of Conyza japonica and their inhibitory activity against nitric oxide production.

Four new sesquiterpenoids, conyterpenols A - D (1-4), along with nineteen known analogues (5-23) were isolated from the aerial parts of Conyza japonica. The structures of 1-4 were determined through spectroscopic analysis, while their absolute configurations were determined by comparison of calculated and experimental electronic circular dichroism (ECD) spectra. Conyterpenol D (4) was a new type of sesquiterpenoid with a seven-membered lactone ring. Compounds 1-23 were evaluated for their inhibitory activity against LPS-induced nitric oxide production in RAW264.7 macrophages and cytotoxicity against human hepatoma cell line (HepG2) and human breast adenocarcinoma cell line (MCF-7). Compounds 3, 4, and 12 displayed moderate inhibition against NO production with IC50 values in the range of 26.4-33.6 µM. And all compounds showed no obvious cytotoxicity against these two cancer cell lines at 100 µM.

Meroterpenoids with Antitumor Activities from Guava (Psidium guajava).

Psidium guajava L., a species native to South America, has been widely cultivated in the tropical and subtropical areas of China for its popular fruits. The preliminary analysis by liquid chromatography-ultraviolet (LC-UV) indicated the presence of meroterpenoids in the fruits of P. guajava (guava). Subsequent fractionation of the petroleum ether extract resulted in the identification of two new meroterpenoids, psiguajavadials A (1) and B (2), together with 14 previously described meroterpenoids (3-16). Their structures were fully elucidated by comprehensive spectroscopic techniques and theoretical calculations. All of the meroterpenoids showed cytotoxicities against five human cancer cell lines, with guajadial B (12) being the most effective having an IC50 value of 150 nM toward A549 cells. Furthermore, biochemical topoisomerase I (Top1) assay revealed that psiguajavadial A (1), psiguajavadial B (2), guajadial B (12), guajadial C (14), and guajadial F (16) acted as Top1 catalytic inhibitors and delayed Top1 poison-mediated DNA damage. The flow cytometric analysis indicated that the new meroterpenoids psiguajavadials A (1) and B (2) could induce apoptosis of HCT116 cells. These data suggest that meroterpenoids from guava fruit could be used for the development of antitumor agents.

Diterpenoids with diverse scaffolds from Vitex trifolia as potential topoisomerase I inhibitor.

Eleven new compounds, including six labdane (1-6), three halimane (7-9), and two clerodane (10-11) diterpenoids and 16 known analogues (12-27), were isolated from the leaves of Vitex trifolia. The structures of 1-11 were established by extensive 1D- and 2D-NMR and HRMS spectroscopic data. The absolute configurations of compounds 3, 7, and 10 were assigned using X-ray diffraction. Compounds 1-27 were evaluated for DNA topoisomerases I (Top1) inhibitory activity and cytotoxicity against HCT 116 cells. Compounds 8 and 11 exhibited equipotent Top1 inhibitory activity to the positive control, camptothecin (CPT), at 100µM. Compounds 8, 9, 16, and 27 showed moderate cytotoxicity at low micromolar concentrations.

Syntheses of diacyltanshinol derivatives and their suppressive effects on macrophage foam cell formation by reducing oxidized LDL uptake.

A series of diacyltanshinol derivatives were synthesized by esterifying the corresponding o-hydroquinones of tanshinones. The suppressive effects of the synthesized compounds on oxidized low-density lipoprotein (oxLDL) uptake and oxLDL-induced macrophage-derived foam cell formation were evaluated. Our results indicated that the nicotinate derivatives 1a and 2a, modified from tanshinone IIA and cryptotanshinone, showed stronger suppressive activity on oxLDL uptake and the resultant foam cell formation relative to tanshinone IIA. Western Blot analysis indicated that derivatives 1a and 2a could dose-dependently inhibit the expression of oxLDL-induced LOX-1, implying that the suppressive effects of 1a and 2a on oxLDL uptake and foam cell formation could be at least partially attributed to the inhibition of LOX-1 expression in macrophages.

Pharmacophore-based discovery of triaryl-substituted imidazole as new telomeric G-quadruplex ligand.

Discovery of potent and selective ligands for telomeric G-quadruplex DNA is a challenging work. Through a combination approach of pharmacophore model construction, model validation, database virtual screening, chemical synthesis and interaction evaluation, we discovered and confirmed triaryl-substituted imidazole TSIZ01 to be a new telomeric G-quadruplex ligand with potent binding and stabilizing activity to G-quadruplex DNA, as well as a 8.7-fold selectivity towards telomeric G-quadruplex DNA over duplex DNA.

Synthesis and evaluation of novel rutaecarpine derivatives and related alkaloids derivatives as selective acetylcholinesterase inhibitors.

A series of novel rutaecarpine derivatives and related alkaloid derivatives 3-aminoalkanamido-substituted rutaecarpine 4a-f and 7,8-dehydrorutaecarpine 5a-c, and 6-aminoalkanamido-substituted 3-[2-(3-Indolyl)ethyl]-4(3a)-quinazolinones 8a-c, were synthesized and subjected to pharmacological evaluation as acetylcholinesterase (AChE) inhibitors. The synthetic compounds exhibited strong inhibitory activity for AChE and high selectivity for AChE over BuChE. The structure-activity relationships were discussed and their binding conformation and simultaneous interactions mode were further clarified by kinetic characterization and the molecular docking studies.