Abstract
Two new indolizidine alkaloids, crepidatumines C (1) and D (2), together with crepidine (3), isocrepidamine (4), and crepidamine (5) were isolated from the Dendrobium crepidatum Lindl. ex Paxt. X-ray diffraction experiments established the absolute configurations of known compounds 3 and 4. The planar structures and relative configurations of new compounds 1 and 2 were elucidated by extensive spectra analysis including HR-ESI-MS, NMR (1H, 13C, 1H-1H COSY, HSQC, HMBC, and NOESY spectra), and the absolute configurations of 1 and 2 were suggested on the basis of possible biosynthetic pathways. The biological results confirmed that isocrepidamine (4) displayed a potent hypoglycemic effect in vitro without cytotoxicity.
Highlights
Dendrobium, a genus of Orchidaceae, is distributed in south of China [1,2]
The HMBC cross peaks from 6-OH to C-5, C-6, C-7, and C-10 determined the direct connectivities of C-6 with C-5, C-7, and C-10 with a hydroxyl group anchored at C-6.The correlations of H-4 with C-2 and C-3 established the linkage of C-4 with C-2 and C-3
The HMBC cross peaks from 6-OH to C-5, C-6, C-7, and C-1’ determined the direct connectivities of C-6 with C-5, C-7, and C-1’ with a hydroxyl group anchored at C-6.The correlations of H-4 with C-2 and C-3 established the linkage of C-4 with C-2 and C-3
Summary
Dendrobium, a genus of Orchidaceae, is distributed in south of China [1,2]. The stems of several. Is considered as one of the sources of “Shi-Hu” It produces indolizine-type alkaloids, and so far, only several indolizine-type alkaloids and two stilbene derivatives have been isolated from this medicinal plant [4,5,6,7,8,9]. Crepidatumines a and B, with novel skeletons, together with the stereoisomer of dendrocrepidine B and dendrocrepine, were isolated during our previous chemical investigation of this medicinal plant [10]. The biosynthesis of indolizidine alkaloids from the Dendrobium crepidatum Lindl. In order to obtain the potential intermediates or shunt products of the biosynthesis, five indolizidine alkaloids including the two new analogs crepidatumines C (1) and D (2) together with crepidine (3), isocrepidamine (4), and crepidamine (5) were isolated from the total alkaloid extract [5].
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