Uncaria rhynchophylla (not to be confused with Uncaria Tomentosa) is a traditional chinese medicine and Japanese medicine that is used for the treatment of hypertension, convulsive disorders (epilepsy), and for various head ailments such as headache or dizziness. It contains a variety of alkaloid structures, most notably the one named after it (Rhynchophylline) and a potent drug-like alkaloid with the acronym of GME (Geissoschizine methyl ether). It is a component of the popular japanese medicinal formula known as Yokukansan, where it alongside glycyrrhiza uralensis (licorice) seem to mediate the neuroprotective effects.
Studies that use oral ingestion of the herb or isolated alkaloids are only in the animal phases of research at this point in time, but it appears that GME has antipsychotic properties very similar to Aripiprazole (pharmaceutical) on the serotonin and dopamine receptors. The influence on the serotonin receptors also confers some anxiety reducing properties, and can reduce social aggression (thought to be the reason why Yokukansan reduces agitation in elderly persons with dementia).
There is also a neuroprotective effect that is mostly based on preventing the brain's support cells (glial cells, which support the neurons) from activating in response to inflammation. This antiinflammatory effect in the brain appears to underlie anti-epileptic properties with oral ingestion of the herb.
Beyond that, there is potential for this herb to reduce blood pressure secondary to activating nitric oxide signalling but this has not yet been investigated in living systems.