Alkaloids from the hook-bearing branch of Uncariarhynchophylla and their neuroprotective effects against glutamate-induced HT22 cell death
2014
Qi, Wen | Yue, Si-Jia | Sun, Jia-Hong | Simpkins, James W. | Zhang, Lin | Yuan, Dan
One new alkaloid, 4-geissoschizine N -oxide methyl ether (1), was isolated from the EtOH extract of the hook-bearing branch of Uncaria rhynchophylla , together with 10 known alkaloids, 3-epi-geissoschizine methyl ether (2) isolated from U. rhynchophylla for the first time, geissoschizine methyl ether (3), 4-hirsuteine N -oxide (4), hirsuteine (5), hirsutine (6), 3α-dihydro-cadambine (7), 3β-isodihydro-cadambine (8), cadambine (9), strictosamide (10), and akuammigine (11). The structures were elucidated by spectroscopic methods including UV, ESI-QTOF MS, NMR, and circular dichroism experiments. Neuroprotective effects of 1 – 9 were investigated against 3 mM glutamate-induced HT22 cell death. The activity assay showed that 2 , 3 , 5 , and 6 exhibited potent neuroprotective effects against glutamate-induced HT22 cell death. However, only weak neuroprotective activities were observed for 1 , 4 , 7 , 8 , and 9 .
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