Honokiol is a lignan isolated from the bark, seed cones, and leaves of trees belonging to the genus Magnolia.

Extracts from the bark or seed cones of the Magnolia tree have been widely used in traditional medicine in China, Korea, and Japan.

However, its antithrombotic effects could cause hemorrhage especially in patients with conditions that would put them at a higher risk like hemophilia or Von Willebrand disease.

In a 2002 study, researchers induced cell death in fetal rat cortical neurons by directly applying 100μM in vitro.

So potent is honokiol's pro-apoptotic effects that it overcomes even notoriously drug resistant neoplasms such as multiple myeloma and chronic B-cell leukemia.

[17] Honokiol [quantify] has been shown to promote neurite outgrowth and have neuroprotective effects in rat cortical neurons.

[18] Honokiol inhibits platelet aggregation in rabbits in a dose-dependent manner, and protects cultured RAEC against oxidized low density lipoprotein injury.

[19] Studies examining honokiol as a protective therapy against focal cerebral ischemia-reperfusion injury have identified a number of anti-inflammatory pathways.

In in vitro studies, honokiol reduced fMLP (N-formyl-methionyl-leucyl-phenylalanine) and PMA (phorbol-12-myristate-13-acetate) induced neutrophil firm adhesion which is an integral step for infiltration.

However, honokiol has been shown to achieve anxiolysis with fewer motor or cognitive side effects than GABAA receptor agonists such as flurazepam and diazepam.

[1] GABAA receptors control ligand-gated Cl− channels that can help increase seizure thresholds through the influx of chloride anions.

In a study where mice received seven daily injections of honokiol, researchers observed a mild increase in hippocampal levels of glutamate decarboxylase (GAD67) an enzyme that catalyzes the synthesis of GABA.

Honokiol disrupts the interfaces post synaptic density protein (PSD95) and neuronal nitric oxide synthase (nNOS).

[1] PSD95 and nNOS coupling to the NMDA receptor causes a conformational change responsible for the intracellular influx of Ca2+ which could in turn be a pathway for neurotoxicity.

[4] Honokiol was shown to normalize blood glucose levels and prevent body weight gain in diabetic mice by acting as agonist of PPARgamma.

[citation needed] Both Native Americans and Japanese medicine use tea gargles to treat toothaches and sore throats.