Bioactive compounds from Leycesteria formosa.
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3',5'-Cyclic-AMP Phosphodiesterases↗
Biomedical subjects
B H Um
Publications and source records attributed to B H Um.
Note on the use of reciprocity of chiral recognition in designing liquid chromatographic chiral stationary phases.
A new high-performance liquid chromatographic chiral stationary phase (CSP) was prepared from (S)-N-(3,5-dimethylbenzoyl)leucine N-phenyl N-allyl amide. The new CSP was applied for the resolution of N-(3,5-dinitrobenzoyl)-alpha-amino amides and esters and the chromatographic resolution results were compared with those on another CSP derived from (S)-N-(3,5-dimethoxylbenzoyl)leucine N-phenyl N-allyl amide. The new CSP was found to exert greater enantioselectivity than the other one. These results are contrary to what was expected from the reciprocity of chiral recognition. From these results it was concluded that the reciprocity of chiral recognition should be used with some degree of care in developing effective CSPs or in predicting chromatographic resolution behaviors.
Chromatography, High Pressure Liquid↗
Saponins from Strasburgeria robusta.
The isolation of three saponins, 24-hydroxytormentic acid ester glucoside (1), niga-ichigoside F1 (2) and niga-ichigoside F2 (3), from the stem bark of Strasburgeria robusta, an endemic plant from New Caledonia, is reported.
Humans↗
Bioactive acridone alkaloids from Swinglea glutinosa.
A new prenylated acridone alkaloid, 1,3,5-trihydroxy-2,8-bis(3-methylbut-2-enyl)-10-methyl-9-acridone (1), was isolated from the stembark of Swinglea glutinosa, along with three known acridone alkaloids, 5-hydroxynoracronycine (2), 1,3,5-trihydroxy-4-methoxy-2-(3-methylbut-2-enyl)-10-methyl-9-acridone (3), and 1,3,5-trihydroxy-4-methoxy-10-methylacridone (4). The isolated alkaloids were assessed in vitro against chloroquine-sensitive and -resistant Plasmodium falciparum strains and for cytotoxicity using HeLa cells.
Acridines↗
Triterpenoid saponins from Isertia pittieri.
Two new 27-nor-triterpenoid saponins, pyrocincholic acid 3 beta-O-beta-D-quinovopyranosyl-28-[beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranosyl] ester (1) and pyrocincholic acid 3 beta-O-beta-D-quinovopyranosyl(1-->6)-beta-D-glucopyranosyl-28-[beta-D-glucopyranosyl(1-->2)-beta-D-glucopyranosyl] ester (2) were isolated from the stem bark of Isertia pittieri, together with two known bidesmosidic quinovic acid glycosides. The structures of 1 and 2 were determined on the basis of spectroscopic studies.
Chromatography, High Pressure Liquid↗
Effect of pretreatment reagent and hydrogen peroxide on enzymatic hydrolysis of oak in percolation process.
The effect of pretreatment reagent and hydrogen peroxide on enzymatic digestibility of oak was investigated to compare pretreatment performance. Pretreatment reagents used were ammonia, sulfuric acid, and water. These solutions were used without or in combination with hydrogen peroxide in the percolation reactor. The reaction was carried out at 170 degrees C for the predetermined reaction time. Ammonia treatment showed the highest delignification but the lowest digestibility and hemicellulose removal among the three treatments. Acid treatment proved to be a very effective method in terms of hemicellulose recovery and cellulose digestibility. Hemicellulose recovery was 65-90% and digestibilities were >90% in the range of 0.01-0.2% acid concentration. In both treatments, hydrogen peroxide had some effect on digestibility but decomposed soluble sugars produced during pretreatment. Unlike ammonia and acid treatments, hydrogen peroxide in water treatment had a certain effect on hemicellulose recovery as well as delignification. At 1.6% hydrogen peroxide concentration, both hemicellulose recovery and digestibility were about 90%, which were almost the same as those of 0.2% sulfuric acid treatment. Also, digestibility was investigated as a function of hemicellulose removal or delignification. It was found that digestibility was more directly related to hemicellulose removal rather than delignification.
Ammonia↗