Extraction of arbutin and its comparative content in branches, leaves, stems, and fruits of Japanese pear Pyrus pyrifolia cv. Kousui.

Arbutin is a tyrosinase inhibitor and is extensively used as a human skin-whitening agent. This study investigated the optimum conditions for extracting arbutin by ultrasonic homogenization from discarded branches pruned from Japanese pear (Pyrus pyrifolia cv. Kousui) trees. The arbutin content was measured in the branches and also in the leaves, stems, fruit peel, and fruit flesh.

5-Isopropyl-5-methyl-2-sulfanylidene-imidazolidin-4-one.

In the title compound, C7H12N2OS, the 2-sulfanylideneimidazolidin-4-one moiety is nearly planar, with a maximum deviation of 0.054 (2) Å. In the crystal, a pair of N-H⋯O hydrogen bonds and a pair of N-H⋯S hydrogen bonds each form a centrosymmetric ring with an R 2 (2)(8) graph-set motif. The enanti-omeric R and S mol-ecules are alternately linked into a tape along [1-10] via these pairs of hydrogen bonds.

1-Acetyl-5-(4-fluoro-phen-yl)-2-sulfanyl-ideneimidazolidin-4-one.

In the title compound, C11H9FN2O2S, the 2-sulfanylideneimidazolidin-4-one moiety is essentially planar, with a maximum deviation of 0.0183 (14) Å. The mean plane of this moiety is approximately coplanar with the attached acetyl group and perpendicular to the benzene ring, making dihedral angles of 9.70 (14) and 86.70 (6)°, respectively. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds between the amide NH and acetyl C=O groups, forming a C(6) chain along the a-axis direction.

Molecular structure (monomeric and dimeric) and hydrogen bonds in 5-benzyl 2-thiohydantoin studied by FT-IR and FT-Raman spectroscopy and DFT calculations.

In the present work the structural and spectral characteristics of 5-benzyl-2-thiohydantoin (5-BTH) have been studied by methods of infrared, Raman spectroscopy and quantum chemistry. Electrostatic potential surface, optimized geometry, harmonic vibrational frequencies, infrared intensities and activities of Raman scattering were calculated by density functional theory (DFT) employing B3LYP with complete relaxation in the potential energy surface using 6-311G++(d,p) basis set. Our results support the hydrogen bonding pattern proposed by reported crystalline structure. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule are calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. UV-vis spectrum of the compound was recorded in methanol solvent. The TD-DFT calculations have been performed to explore the influence of electronic absorption spectra in the gas phase, as well as in solution environment using PCM and 6-311++G(d,p) basis set. In addition, the thermodynamic properties of the compound were calculated at different temperatures and corresponding relations between the properties and temperature were also studied.

Experimental (FT-IR, FT-Raman, NMR) and theoretical spectroscopic properties of intermolecular hydrogen bonded 1-acetyl-2-thiohydantoin polymorphs.

In this work, use of FT-Raman, FT-IR and (13)C NMR spectroscopies have been made for the full characterization of 1-acetyl-2-thiohydantoin (ACTH). A detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis using single scaling factor. Our results support the hydrogen bonding pattern proposed in the reported crystalline structure. Good reproduction of experimental values is obtained and % error is small in majority of the cases. Isotropic chemical shifts were calculated using gauge-invariant atomic orbital (GIAO) along with several thermodynamic parameters.

Uniformly sized molecularly imprinted polymer for (S)-nilvadipine. Comparison of chiral recognition ability with HPLC chiral stationary phases based on a protein.

Uniformly sized molecularly imprinted polymers (MIPs) for (S)-nilvadipine have been prepared by a multistep swelling and polymerization method using methacrylic acid, 2-(trifluoromethyl)acrylic acid, 2-vinylpyridine, or 4-vinylpyridine (4-VPY) as a functional monomer and ethylene glycol dimethacrylate (EDMA) as a cross-linker. The chiral recognition abilities of the MIPs for nilvadipine and other dihydropyridine calcium antagonists were evaluated using a mixture of sodium phosphate buffer (or water) and acetonitrile or only acetonitrile as the mobile phase. The (S)-nilvadipine-imprinted 4-VPY-co-EDMA polymers gave the highest resolution for nilvadipine among the MIPs prepared. In addition, the enantioseparation of nilvadipine was attained using the (S)-nilvadipine-imprinted EDMA polymers, without use of a functional monomer. 1H NMR and molecular modeling studies suggested a one-to-one hydrogen-bonding-based complex formation of (S)-nilvadipine with 4-VPY in chloroform. These results reveal that the (S)-nilvadipine-imprinted EDMA polymers could recognize the template molecule by its molecular shape, and that in addition to this recognition, hydrophobic and hydrogen-bonding interactions seems to play important roles in the retention and chiral recognition of nilvadipine on the 4-VPY-co-EDMA polymers in hydroorganic mobile phases. By optimizing chromatographic conditions such as column temperature and flow rate, the baseline separation of nilvadipine enantiomers was attained with a short analysis time and with a column efficiency comparable to commercially available chiral stationary phases based on a protein, such as ovomucoid or alpha1-acid glycoprotein.