Abstract
Uncaria rhynchophylla is commonly recognized as a traditional treatment for dizziness, cerebrovascular diseases, and nervous disorders in China. Previously, the neuro-protective activities of the alkaloids from U. rhynchophylla were intensively reported. In current work, three new indole alkaloids (1–3), identified as geissoschizic acid (1), geissoschizic acid N4-oxide (2), and 3β-sitsirikine N4-oxide (3), as well as 26 known analogues were isolated from U. rhynchophylla. However, in the neural stem cells (NSCs) proliferation assay for all isolated compounds, geissoschizic acid (1), geissoschizic acid N4-oxide (2), isocorynoxeine (6), isorhynchophylline (7), (4S)-akuammigine N-oxide (8), and (4S)-rhynchophylline N-oxide (10) showed unexpected inhibitory activities at 10 μM. Unlike previous neuro-protective reports, as a warning or caution, our finding showcased a clue for possible NSCs toxicity and the neural lesions risk of U. rhynchophylla, while the structure–activity relationships of the isolated compounds were discussed also.
Highlights
The dried stem and hook of Uncaria rhynchophylla, named as Gou-teng or Cat’s claw, was used for treatment of dizziness, cerebrovascular diseases, and nervous disordersElectronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.X
Besides reported neuro-protective activities, the tested results shed a light on the possible neural stem cells (NSCs) toxicity and and the neural lesions risk of U. rhynchophylla, as a warning or caution
In the tetracyclic indole alkaloid (1), the absolute configuration of C-3 was determined as S according to a positive cotton effect at 267 nm, while negative
Summary
The dried stem and hook of Uncaria rhynchophylla, named as Gou-teng or Cat’s claw, was used for treatment of dizziness, cerebrovascular diseases, and nervous disorders. Up to now, detailed phytochemical research resulted in more than 90 indole alkaloids from U. rhynchophylla [2]. The neuro-protective activities of the total alkaloids and the main monomeric indoles from U. rhynchophylla were reported [3,4,5,6,7]. Chen Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, People’s Republic of China. As our ongoing search for novel and bioactive alkaloids as well as further NSCs related evaluation [16, 18], the detailed chemical investigation on hook-bearing branches of U. rhynchophylla was carried out. Besides reported neuro-protective activities, the tested results shed a light on the possible NSCs toxicity and and the neural lesions risk of U. rhynchophylla, as a warning or caution. The structure–activity relationships of the compounds mentioned above were discussed by structural analysis
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