Buxus alkaloids. Part VII. The isolation and the constitutions of ten new alkaloids from the weak-base fractions of two species, B. microphylla Sieb. et Zucc. var. suffruticosa Makino and B. microphylla Sieb. et Zucc. var. suffruticosa Makino forma major Makino
作者:T. Nakano、S. Terao、Y. Saeki
DOI:10.1039/j39660001412
日期:——
Investigation of the weak-base fractions of two species, B. microphylla Sieb. et Zucc. var. suffruticosa Makino and B. microphylla Sieb. et Zucc. var. suffruticosa Makino forma major Makino, has led to the isolation of ten new alkaloids. In addition, another new alkaloid was isolated from the strong-base fraction of the latter species. These alkaloids are structurally closely related, and their interconversion
4-Epicycloeucalenone and 4-Epicyclomusalenone: Two 3-Oxo-28-norcycloartanes from the Fruit Peel of Musa sapientum L.
作者:Toshihiro AKIHISA、Yumiko KIMURA、Wilhelmus C. M. C. KOKKE、Sei-ichi TAKASE、Ken YASUKAWA、Aiko JIN-NAI、Toshitake TAMURA
DOI:10.1248/cpb.45.744
日期:——
Two 3-oxo-28-norcycloartane-type triterpenes, 4-epicycloeucalenone and 4-epicyclomusalenone, and two known 3-oxo-29-norcycloartanes, cycloeucalenone and cyclomusalenone, were isolated from the n-hexane extract of the fruit peel of Musa sapientum L. (banana). The structures of the 28-norcycloartanes were determined by spectroscopic and chemical methods.
Homology Modeling and Site-Directed Mutagenesis Reveal Catalytic Key Amino Acids of 3<i>β</i>-Hydroxysteroid-Dehydrogenase/C4-Decarboxylase from Arabidopsis
3beta-hydroxysteroid-dehydrogenase/C4-decarboxylase (3betaHSD/D). We recently identified Arabidopsis (Arabidopsis thaliana) 3betaHSD/D as a bifunctional short-chain dehydrogenase/reductase protein. We made use of three-dimensional homology modeling to identify key amino acids involved in 4alpha-carboxy-sterol and NADbinding and catalysis. Key amino acids were subjected to site-directed mutagenesis, and the
At3betaHSD/D1 endoplasmic reticulum-retrieval sequence restored growth and ergosterol synthesis in erg26. An in vitro enzymatic assay revealed high 3betaHSD/D activity for both isoenzymes in the corresponding microsomal extracts. The two At3betaHSD/D isoenzymes showed similar substratespecificities that required free 3beta-hydroxyl and C-4-carboxyl groups but were quite tolerant in terms of variations of