Abstract: The bark of Magnolia officinalis is a well-known Traditional Chinese Medicine. In the present study, two new alkaloids, named (S)-4-keto-magnoflorine (6) and (R)-3,4-dehydromagnocurarine (11), together with seven known alkaloids: (S)-magnoflorine (5), trans/cis N-feruloylputrescine (7/8), (R)-magnocurarine (10), (S)-tembetarine (12), (R)-oblongine (14), and (R)-asimilobine (17) were isolated and their structures elucidated by spectroscopic methods, including 1D, 2D NMR, and HRESI-MS. The absolute configurations of the isoquinoline alkaloids 5, 6, 10–12, 14, and 17 were determined by CD. In vitro inhibitory activities against aldose reductase, lipase, α-glucosidase, DPP–IV and three cancer cell lines (A549, Bel-7402, and HCT-8) were evaluated for all isolated compounds. However, all compounds showed weak activities in all tests at the same concentration as the positive control drugs. An HPLC-ESI-MSn method has been established for screening of alkaloids in the bark of M. officinalis. A total of 23 alkaloids were identified or tentatively characterized; including 13 aporphines, eight benzylisoquinolines and two amides. Plausible fragmentation pathways of the representative compounds 6, 7/8, 11, and 17 were proposed in the present study.
Keywords: Magnolia officinalis; alkaloid; HPLC-MSn; 4-keto-magnoflorine; 3,4-dehydromagnocurarine
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Yan, R.; Wang, W.; Guo, J.; Liu, H.; Zhang, J.; Yang, B. Studies on the Alkaloids of the Bark of Magnolia officinalis: Isolation and On-line Analysis by HPLC-ESI-MSn. Molecules 2013, 18, 7739-7750.
Yan R, Wang W, Guo J, Liu H, Zhang J, Yang B. Studies on the Alkaloids of the Bark of Magnolia officinalis: Isolation and On-line Analysis by HPLC-ESI-MSn. Molecules. 2013; 18(7):7739-7750.
Yan, Renyi; Wang, Weihao; Guo, Jian; Liu, Hongliang; Zhang, Jianyong; Yang, Bin. 2013. "Studies on the Alkaloids of the Bark of Magnolia officinalis: Isolation and On-line Analysis by HPLC-ESI-MSn." Molecules 18, no. 7: 7739-7750.