Aim To study chemical constituents from Ampelopsis grossedentata. Methods Separation and purification were performed by using silica gel, polyamide, reverse-phase silica gel, Sephadex LH-20 column chromatographic tech...Aim To study chemical constituents from Ampelopsis grossedentata. Methods Separation and purification were performed by using silica gel, polyamide, reverse-phase silica gel, Sephadex LH-20 column chromatographic techniques and silica gel PTLC. Structures were determined by means of physicochemical properties and spectral analysis. Results Four flavonoids were separated and identified from Ampelopsis grossedentata including dihydromyricetin (1), myricetin (2), myricitrin (3), and myricetin-3-O-β-D-galactopy...展开更多
Water-soluble, nondialyzable Maillard polymers were prepared by reacting D-xylose with 15N-glycine (and/or glycine) at 68 ℃ and pH 8.0 at equimolar concentrations of 1, 0.5 and 0.1 mol L-1, respectively,for 13 days a...Water-soluble, nondialyzable Maillard polymers were prepared by reacting D-xylose with 15N-glycine (and/or glycine) at 68 ℃ and pH 8.0 at equimolar concentrations of 1, 0.5 and 0.1 mol L-1, respectively,for 13 days and partitioned into acid-insoluble (MHA) and acid-soluble (MFA) fractions. The nitrogen forms in these polymers were studied by using the 15N cross polarization-magic angle spinning nuclear magnetic resonance (CPMAS NMR) technique in combination with chemical methods. The 15N nuclear magnetic resonance (NMR) data showed that while the yield, especially the MHA/MFA ratio, varied considerably with the concentrations of the reactants, the nitrogen distribution patterns of these polymers were quite similar.From 65% to 70% of nitrogen in them was in the secondary amide and/or indole form with 24%~25% present as aliphatic and/or aromatic ammes and 5% to 11% as pyrrole and/or pyrrole-like nitrogen. More than half (50%~77%) of the N in these polymers were nonhydrolyzable. The role of Maillard reaction in the formation of nonhydrolyzable nitrogen in soil organic matter is discussed.展开更多
文摘Aim To study chemical constituents from Ampelopsis grossedentata. Methods Separation and purification were performed by using silica gel, polyamide, reverse-phase silica gel, Sephadex LH-20 column chromatographic techniques and silica gel PTLC. Structures were determined by means of physicochemical properties and spectral analysis. Results Four flavonoids were separated and identified from Ampelopsis grossedentata including dihydromyricetin (1), myricetin (2), myricitrin (3), and myricetin-3-O-β-D-galactopy...
文摘Water-soluble, nondialyzable Maillard polymers were prepared by reacting D-xylose with 15N-glycine (and/or glycine) at 68 ℃ and pH 8.0 at equimolar concentrations of 1, 0.5 and 0.1 mol L-1, respectively,for 13 days and partitioned into acid-insoluble (MHA) and acid-soluble (MFA) fractions. The nitrogen forms in these polymers were studied by using the 15N cross polarization-magic angle spinning nuclear magnetic resonance (CPMAS NMR) technique in combination with chemical methods. The 15N nuclear magnetic resonance (NMR) data showed that while the yield, especially the MHA/MFA ratio, varied considerably with the concentrations of the reactants, the nitrogen distribution patterns of these polymers were quite similar.From 65% to 70% of nitrogen in them was in the secondary amide and/or indole form with 24%~25% present as aliphatic and/or aromatic ammes and 5% to 11% as pyrrole and/or pyrrole-like nitrogen. More than half (50%~77%) of the N in these polymers were nonhydrolyzable. The role of Maillard reaction in the formation of nonhydrolyzable nitrogen in soil organic matter is discussed.
