Cat’s Claw (uncaria tomentosa)- NMDA (a type of glutamate receptor) inhibitor.  Should be used with caution as it is a immune system activator and may be problematic for some. “Rhynchophylline and isorhynchophylline are major tetracyclic oxindole alkaloid components of Uncaira species, which have been long used as medicinal plants. In this study, the effects of rhynchophylline and isorhynchophylline on the ionotropic and metabotropic glutamatereceptor-mediated current responses were examined using Xenopus oocytes injected with total RNA prepared from rat cortices or cerebelli.” “hese results suggest that rhynchophylline and isorhynchophylline act as noncompetitive antagonists of the NMDA receptor and that this property may contribute to the neuroprotective and anticonvulsant activity of the Uncairaspecies [...]