Identification of Antiglycative Compounds in Japanese Red Water Pepper (Red Leaf Variant of the Persicaria hydropiper Sprout)

Glycation, the nonenzymatic reaction between proteins and excess blood sugar, is implicated in multiple disorders and occurs via the formation and accumulation of advanced glycation end products (AGEs). In our previous studies, we demonstrated that the red-leaf variant of the Persicaria hydropiper sprout (Japanese red water pepper, Benitade) is one of the potent plants that inhibit formation of AGEs. In this study, we aimed to identify antiglycative compounds in Benitade. Benitade extracts were prepared with hot water, then fractionated by using high-performance liquid chromatography (HPLC). The antiglycative efficacy of each fraction was evaluated by measuring the formation of fluorescent AGEs (Ex 370 nm/Em 440 nm). Two fractions, which contained peaks at 26.4 min and 31.8 min, showed potent antiglycative efficacy. When we hydrolyzed these peaks, they shifted to 32.5 and 41.4 min, which are the same retention times as cyanidin and quercetin, respectively. Based on thin-layer chromatography, both compounds contained galactose. Finally, ultrahigh-performance liquid chromatography/quadrupole-time of flight mass spectrometry (UHPLC-QqTOF-MS) analyses were performed to determine the structure of those compounds. Overall, we identified two glycosides, cyanidin 3-O-galactoside (idaein) and quercetin 3-O-galactoside (hyperin), as representative antiglycative compounds in Benitade

Reverse Regioselectivity in Reductive Ring Opening of Epoxide Enabled by Zirconocene and Photoredox Catalysis

A ring opening of epoxide with zirconocene and photoredox catalysis has been developed. Compared to the ring opening methods with titanocene, the present protocol exhibited reverse regioselectivity to afford more-substituted alcohols via putative less-stable radicals. DFT calculations indicated that the observed regioselectivity could be explained by shifting the transition states to more reactant-like structures by changing the metal center of the metallocene catalyst

DFT Studies on the Mechanism of the Iridium-Catalyzed Formal [4 + 1] Cycloaddition of Biphenylene with Alkenes

Recently, we reported an Ir-catalyzed formal [4 + 1] cycloaddition of biphenylenes with alkenes, which gave 9,9-disubstituted fluorenes in moderate to excellent yields. We proposed a reaction mechanism that involved the intermolecular insertion of alkenes, β-elimination, and intramolecular insertion based on the results of experimental mechanistic studies. Herein, we further support the proposed mechanism by density functional theory calculations and explain why [4 + 1] cycloaddition proceeds rather than conventional [4 + 2] cycloaddition

Aggregation Number in Water/<i>n</i>‑Hexanol Molecular Clusters Formed in Cyclohexane at Different Water/<i>n</i>‑Hexanol/Cyclohexane Compositions Calculated by Titration ¹H NMR

Upon titration of <i>n</i>-hexanol/cyclohexane mixtures of different molar compositions with water, water/<i>n</i>-hexanol clusters are formed in cyclohexane. Here, we develop a new method to estimate the water and <i>n</i>-hexanol aggregation numbers in the clusters that combines integration analysis in one-dimensional ¹H NMR spectra, diffusion coefficients calculated by diffusion-ordered NMR spectroscopy, and further application of the Stokes–Einstein equation to calculate the hydrodynamic volume of the clusters. Aggregation numbers of 5–15 molecules of <i>n</i>-hexanol per cluster in the absence of water were observed in the whole range of <i>n</i>-hexanol/cyclohexane molar fractions studied. After saturation with water, aggregation numbers of 6–13 <i>n</i>-hexanol and 0.5–5 water molecules per cluster were found. O–H and O–O atom distances related to hydrogen bonds between donor/acceptor molecules were theoretically calculated using density functional theory. The results show that at low <i>n</i>-hexanol molar fractions, where a robust hydrogen-bond network is held between <i>n</i>-hexanol molecules, addition of water makes the intermolecular O–O atom distance shorter, reinforcing molecular association in the clusters, whereas at high <i>n</i>-hexanol molar fractions, where dipole–dipole interactions dominate, addition of water makes the intermolecular O–O atom distance longer, weakening the cluster structure. This correlates with experimental NMR results, which show an increase in the size and aggregation number in the clusters upon addition of water at low <i>n</i>-hexanol molar fractions, and a decrease of these magnitudes at high <i>n</i>-hexanol molar fractions. In addition, water produces an increase in the proton exchange rate between donor/acceptor molecules at all <i>n</i>-hexanol molar fractions