Preparation and characterization of inclusion complexes of antitumor camptothecin with cucurbit[n = 7, 8]urils

The slightly water-soluble anticancer drug camptothecin (CPT) and its inclusion complexes with cucurbit[n = 7, 8]uril (Q[n] (n = 7, 8)) were investigated. The formation of 1:2 complexes with Q[n] (n = 7, 8) in aqueous solution was confirmed by fluorescence spectroscopy and the apparent stability constants were determined to be higher than 3.01 × 10¹² L²/mol². The solid inclusion complexes of CPT and Q[n] (n = 7, 8) were also prepared by the co-evaporation method and characterized by Fourier transformation-infrared spectroscopy, differential scanning calorimetry and powder X-ray diffraction. Aqueous solubility and dissolution studies indicate that the complexes exhibited significantly increased dissolution rates compared with the pure drug and physical mixtures. The potential of Q[7] or Q[8] for stabilizing lactone modality of CPT was investigated by the High Performance Liquid Chromatography (HPLC) method. The results reveal more than 63% CPT lactone form (active form) in CPT-Q[7] or Q[8] complexes compared to only 36% CPT lactone form in the absence of Q[7] or Q[8] after being incubated in the phosphate buffer solution (pH 7.4 at 37°C) for 5 h.     

Redox Multifunctionality in a Series of PtII Dithiolene Complexes of a Tetrathiafulvalene‐Based Diphosphine Ligand

The redox‐active and chelating diphosphine, 3,4‐dimethyl‐3′,4′‐bis(diphenylphosphino)‐tetrathiafulvalene, denoted as P2 , is engaged in a series of platinum complexes, [(P2)Pt(dithiolene)], with different dithiolate ligands, such as 1,2‐benzenedithiolate (bdt), 1,3‐dithiole‐2‐thione‐4,5‐dithiolate (dmit), and 5,6‐dihydro‐1,4‐dithiin‐2,3‐dithiolate (dddt). The complexes are structurally characterized by X‐ray diffraction, together with a model compound derived from bis(diphenylphosphino)ethane, namely, [(dppe)Pt(dddt)] . Four successive reversible electron‐transfer processes are found for the [(P2)Pt(dddt)] complex, associated with the two covalently linked but electronically uncoupled electrophores, that is, the TTF core and the platinum dithiolene moiety. The assignments of the different redox processes to either one or the other electrophore is made thanks to the electrochemical properties of the model compound [(dppe)Pt(dddt)] lacking the TTF redox core, and with the help of theoretical calculations (DFT) to understand the nature and energy of the frontier orbitals of the [(P2)Pt(dithiolene)] complexes in their different oxidation states. The first oxidation of the highly electron‐rich [(P2)Pt(dddt)] complex can be unambiguously assigned to the redox process affecting the Pt(dddt) moiety rather than the TTF core, a rare example in the coordination chemistry of tetrathiafulvalenes acting as ligands.     

Regio- and enantioselective intermolecular hydroacylation: substrate-directed addition of salicylaldehydes to homoallylic sulfides

We report a Rh-catalyzed, regio- and enantioselective intermolecular olefin hydroacylation under mild conditions. Hydroacylations between homoallylic sulfides, containing a substrate-bound directing group, and salicylaldehyde derivatives occur in the presence of a spiro-phosphoramidite ligand, (R)-SIPHOS-PE, to give α-branched ketones in >20:1 selectivity and up to 97% ee. Our conditions are also applicable to the asymmetric intermolecular hydroacylation of 1,2-disubstituted olefins.     

Tuning the band-gap energy of TiO2-xCx nanoparticle for high performance photo-catalyst

We describe a method tuning the band-gap energy (E_g) of visible light sensitive TiO_2-xC_x nanoparticle. E_g tends to become smaller with the increase in the amount of carbon dopant in TiO_2-xC_x nanoparticle due to the increase in excess electrons. Photo-catalytic oxidative activity, however, did not depend on only the value of E_g, but also the energy level of valence band. TiO_1.96C_0.04 nanoparticle having E_g of 2.6 eV showed outstanding performance in oxidative decomposition of phenol under the irradiation of visible light.     

Chemical constituents of the ethyl acetate extract of Belamcanda chinensis (L.) DC roots and their antitumor activities

An activity-directed fractionation and purification process was used to isolate antitumor compounds from the roots of Belamcanda chinensis (L.) DC. The ethyl acetate extract showed greater antitumor activities than the other extracts, consequently leading to the isolation of 18 compounds identified as β-sitosterol (1), dausterol (2), quercetin (3), kampferol (4), shikimic acid (5), gallic acid (6), ursolic acid (7), betulin (8), betulonic acid (9), betulone (10), tectoridin (11), irisflorentin (12), 4′,5,6-trihydroxy-7-methoxyisoflavone (13), tectorigenin (14), irilins A (15), iridin (16), irigenin (17), and iristectongenin A (18). Compounds 3-10, 13, and 15 were isolated from B. chinensis for the first time. Compounds 4 and 7-10 showed potent cytotoxic activities against PC3, MGC-803, Bcap-37, and MCF-7 cell lines. The mechanism of the antitumor action of compound 7 was preliminarily investigated through acridine orange/ethidium bromide (AO/EB) staining, Hoechst 33258 staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, which indicated the growth inhibition of MGC-803 cells via the induction of tumor cell apoptosis.     

Simultaneous determination of catecholamines and amino acids by micellar electrokinetic chromatography with laser-induced fluorescence detection

A selective and sensitive method was developed for separation and simultaneous determination of catecholamines and amino acids by MEKC with LIF. Interestingly enough, such work has been firstly performed on catecholamines derivatized with 4-chloro-7-nitro-2,1,3-benzoxadiazole and the detailed derivatization mechanism was discussed. After derivatization at 60 degrees C for 20 min, NBD-labeled catecholamines and amino acids were separated in a buffer system containing 10 mM sodium tetraborate-Na2HPO4, 20 mM SDS, and 10% v/v ACN at pH 9.75. SDS micelles were employed to improve the fluorescence intensity of catecholamine derivatives efficiently. Under optimum conditions, two catecholamines and 11 amino acids were separated in a short 13 min analysis time and the RSDs for migration time and peak area were less than 0.60 and 6.50%, respectively. The method was successfully applied for the quantification of catecholamines and amino acids in Portulaca oleracea L., human urine sample, and mixed injection sample.     

Anticomplement and antimicrobial activities of flavonoids from Entada phaseoloides

Seventeen flavonoids isolated from the extracts of the stem of Entada phaseoloides were investigated for their anticomplement (both classic and alternative pathways) and antimicrobial activities against Gram-positive bacteria (MRSA, MSSA, Standard Enterococcus and Bacillus subtilis), Gram-negative bacteria (Escherichia coli, Pseudomonas aeuroginosa) and the yeast-like pathogenic fungus Candida albicans. The anticomplement studies revealed a dose-dependent activity among isolated quercetin, luteolin, apigenin, galangin, 5,2',5'-trihydroxy-3,7,4'-trimethoxyflavone-2'-O-beta-D-glucoside (+)-3,3',5',5,7-pentahydroflavanone, (+)-dihydrokaempferol, (-)-epicatechin, (+)-catechin, naringenin, and 5,7,3',5'-tetrahydroxyflavanone, and the antimicrobial results indicated that quercetin, 5,7,4'-trihydroxy-3'-methoxyflavonol and galangin produced the inhibitory activities against MRSA, MSSA, and Standard Enterococcus, while luteolin and rhamnocitrin displayed inhibition against only MRSA and MSSA. To the best of our knowledge, this is the first report that describes the anticomplement and antimicrobial activities of the stem of E. phaseoloides.     

Chiral guanidine-catalyzed asymmetric direct vinylogous Michael reaction of α,β-unsaturated γ-butyrolactams with alkylidene malonates

The asymmetric direct vinylogous Michael reaction of α,β-unsaturated γ-butyrolactams with alkylidene malonates has been developed. Various 5-substituted 3-pyrrolidin-2-ones were obtained in high yields (up to 93%) with excellent stereoselectivities (up to 94% ee, 95 : 5 dr), using a novel bifunctional C(1)-symmetric guanidine organocatalyst embodied a secondary amine subunit.