UV protection and singlet oxygen quenching activity of aloesaponarin I

The UV protection and singlet oxygen quenching of aloesaponarin I have been studied by means of laser spectroscopy. The excited-state intramolecular proton transfer that provides the UV protection takes place along only one of the molecule's two intramolecular hydrogen bonds, and this can be understood by considering the nodal pattern of the wave function. The functional groups participating in the excited-state intramolecular proton transfer also play important roles in the singlet oxygen quenching. Aloesaponarin I has a quenching rate constant larger than that of vitamin E and has a long duration of action due to its resistance to UV degradation and chemical attacks by singlet oxygen and free radicals.     

Mesopore-free hollow silica particles with controllable diameter and shell thickness via additive-free synthesis

Mesopore-free hollow silica particles with a spherical shape, smooth surface, and controllable diameter (from 80 to 300 nm) and shell thickness (from 2 to 25 nm) were successfully prepared using an additive-free synthesis method. Different from other hollow particle developments, a mesopore-free shell was produced because of the absence of additive. Although common reports pointed out the importance of the additional additive in pasting and growing silica on the surface of a template, here we preferred to exploit the effect of the template charge in gaining the silica coating process. To form the silica, basic amino acid (i.e., lysine) was used as a catalyst to replace ammonia or hydrazine, which is harmless and able to control the silica growth and produce hollow particles with smooth surfaces. Control of the particle diameter was drastically achieved by altering the size of the template. The flexibility of the process in controlling the shell thickness was predominantly attained by varying the compositions of the reactants (i.e., silica source and catalyst). The present mesopore-free hollow particles could be efficiently used for various applications, especially for thermal insulator and optical devices because of their tendency not to adsorb large molecules, as confirmed by adsorption analysis.     

Syntheses and properties of tetraaza‐, diaza‐, tetraoxa‐, and dioxa‐metacyclophanes

Metacyclophanes were prepared by cyclization reactions between bis(chloromethyl) compounds and piperazine, primary amines, or ethylene glycol. The ¹H nmr relaxation time (T₁) measurements indicated that the macrocycles feature the up and down motion of the aromatic units around the XCH₂Ar (X = N, O) methylene moieties as the axes. Metacyclophanes incorporating piperazine units showed high complexation ability for alkaline metal cations.     

A photoreactive small-molecule probe for 2-oxoglutarate oxygenases

2-oxoglutarate (2-OG)-dependent oxygenases have diverse roles in human biology. The inhibition of several 2-OG oxygenases is being targeted for therapeutic intervention, including for cancer, anemia, and ischemic diseases. We report a small-molecule probe for 2-OG oxygenases that employs a hydroxyquinoline template coupled to a photoactivable crosslinking group and an affinity-purification tag. Following studies with recombinant proteins, the probe was shown to crosslink to 2-OG oxygenases in human crude cell extracts, including to proteins at endogenous levels. This approach is useful for inhibitor profiling, as demonstrated by crosslinking to the histone demethylase FBXL11 (KDM2A) in HEK293T nuclear extracts. The results also suggest that small-molecule probes may be suitable for substrate identification studies.     

Synthesis of N,N′-bridged azacalixarenes

The one-pot reaction between bis(hydroxymethyl)phenol derivatives and diamines or triamines afforded novel azacalixarenes with bridged structures. Basket-type macrocycles of cone conformations, molecules that contained two aza[3.1.1.1]calixarene skeletons connected by a chain, or novel saucer-type azacalixarenes were obtained from the reaction. Structures of some of them were determined by crystallographic analyses.     

Glycosides of Atractylodes ovata

A new coumarin glycoside and a new glycoside of an acetylene derivative were isolated from the water-soluble portion of the methanolic extract of Atractylodes ovata rhizome together with eight known compounds. Their structures were characterized as scopoletin beta-D-xylopyranosyl-(1-->6)-beta-D-glucopyranoside and (2E)-2-decene-4,6-diyne-1,8-diol 8-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside, respectively, based on chemical and spectroscopic investigations. A comparison of the polar constituents among Atractylodes japonica, Atractylodes lancea, and A. ovata is led to the conclusion that A. ovata is distinguishable from A. lancea and A. japonica, as also shown by phylogenetic analysis.