Two new rotenoid glycosides from the rhizomes of Stemona curtisii Hook. f.

Two new rotenoid glycosides named stemonal 11-O-ß-D-glucopyranoside and 6-O-methylstemonal 11-O-ß-D-glucopyranoside together with ten known metabolites were isolated from the rhizomes of Stemona curtisii. The chemical structures of the new compounds were elucidated based on the analysis of their 1D and 2D NMR and HRESIMS, while the sugar unit and absolute configuration were determined by chemical hydrolysis and ECD analysis. Among the tested compounds for anti-α-glucosidase assay, stemonal showed an inhibitory effect (IC50 = 38.67 µM), which is 2.4-fold more potent than acarbose. Cytotoxic evaluation against the lung adenocarcinoma A549 cell line indicated that none of the compounds were strongly active to suppress the cancer cell growth at 100 µM. This work describes the occurrence of rotenoids bearing a sugar moiety, which are reported for the first time in the genus Stemona. The isolated compound's α-glucosidase inhibitory potential provides insight for further investigation of natural rotenoids as anti-diabetic agents.

DFT insight into metals and ligands substitution effects on reactivity of phenoxy-imine catalysts for ethylene polymerization.

The reaction mechanism of ethylene (ET) polymerization catalyzed by the phenoxy-imine (FI) ligands using DFT calculations was studied. Among five possible isomers, isomer A which has an octahedral geometry and a (cis-N/trans-O/cis-Cl) arrangement is the most stable pre-reaction Ti-FI dichloride complex. The isomer A can be activated by MAO to form the active catalyst and the active form was used for the study of the mechanism for Ti-FI. The second ethylene insertion was found to be the rate-determining step of the catalyzed ethylene polymerization. To examine the effect of group IVB transition metals (M = Ti, Zr, Hf) substitutions, calculated activation energies at the rate-determining step (EaRDS) were compared, where values of EaRDS of Zr < Hf < Ti agree with experiments. Moreover, we examined the effect of substitution on (O, X) ligands of the Ti-phenoxy-imine (Ti-1) based catalyst. The results revealed that EaRDS of (O, N) > (O, O) > (O, P) > O, S). Hence, the (O, S) ligand has the highest potential to improve the catalytic activity of the Ti-FI catalyst. We also found the activation energy to be related to the Ti-X distance. In addition, a novel Ni-based FI catalyst was investigated. The results indicated that the nickel (II) complex based on the phenoxy-imine (O, N) ligand in the square-planar geometry is more active than in the octahedral geometry. This work provides fundamental insights into the reaction mechanism of M - FI catalysts which can be used for the design and development of M - FI catalysts for ET polymerization.

Schomburginones A‒J, geranylated benzophenones from the leaves of Garcinia schomburgkiana and their cytotoxic and anti-inflammatory activities.

Ten undescribed benzophenones, schomburginones A-J, together with 14 known analogs were isolated from the leaves of Garcinia schomburgkiana, an edible plant native to the Indochina region. The structures of the undescribed compounds were elucidated by NMR combined with HRMS spectroscopy, while their absolute configurations were determined using ECD and single-crystal X-ray diffraction analysis. The isolated metabolites represent benzophenone derivatives containing a modified monoterpene unit, including tri- and tetracyclic skeletons, which are rarely found in genus Garcinia. The cytotoxic evaluation on three cancerous cell lines demonstrated that schomburginone G, schomburginone H, and 3-geranyl-2,4,6-trihydroxybenzophenone were active against HeLa cells with IC50 values in the range of 12.2-15.7 µM, respectively, and selective compared to the non-cancerous L929 cells (SI > 3.5). In addition, the three cytotoxic compounds together with clusiacyclol A showed significant NO inhibitory activity in RAW 264.7 macrophage cells over 85% inhibition without obvious cytotoxicity at a final concentration of 100 µM. The promising activities of these compounds in cytotoxic and anti-inflammatory assays make them attractive for further study in the development of anticancer drugs.

Garcowacinols A-J, cytotoxic polyprenylated benzoylphloroglucinol derivatives from the twigs of Garcinia cowa.

Ten undescribed polyprenylated benzoylphloroglucinol derivatives named garcowacinols A‒J (1-10) and four known analogues (11-14) were isolated from the twigs of Garcinia cowa. Their structures were determined by spectroscopic data analysis (1D and 2D NMR and HRESIMS), and their absolute configurations were established based on NOESY and ECD data. All isolated compounds were evaluated for their cytotoxicity against five types of human cancer cells (KB, HeLa S3, MCF-7, Hep G2, and HT-29) as well as Vero cells by MTT colorimetric assay. Garcowacinol C was significantly active against all the five cancer cells with IC50 values in the range of 0.61-9.50 µM. Selective proliferative inhibitions were observed on garcowacinol F and 7-epiclusianone against KB cells, and guttiferone Q toward MCF-7 cells with IC50 values less than 10 µM.

How strong is the edge effect in the adsorption of anticancer drugs on a graphene cluster?

The adsorption of nucleobase-analog anticancer drugs (fluorouracil, thioguanine, and mercaptopurine) on a graphene flake (C54H18) was investigated by shifting the site at which adsorption occurs from one end of the sheet to the other end. The counterpoise-corrected M06-2X/cc-pVDZ binding energies revealed that the binding stability decreases in the sequence thioguanine > mercaptopurine > fluorouracil. We found that adsorption near the middle of the sheet is more favorable than adsorption near the edge due to the edge effect. This edge effect is stronger for the adsorption of thioguanine or mercaptopurine than for fluorouracil adsorption. However, the edge effect reduces the binding energy of the drug to the flake by only a small amount, <5 kcal/mol, depending on the adsorption site and the alignment of the drug at this site.