methysticin

Methysticin is one of the six major kavalactones found in the kava plant. It enhances the activity of the GABAA receptor, acting as a positive modulator without affecting the benzodiazepine binding site. This effect is attributed to structural features such as its angular lactone ring and is similar in strength to other kavalactones like kavain and dihydromethysticin. Methysticin also induces the liver enzyme CYP1A1, which plays a role in the toxification of benzo[a]pyrene into a highly carcinogenic metabolite, although such induction has not been observed in vivo in humans or animals. Additionally, methysticin is a mechanism-based inactivator of CYP2C9, irreversibly inhibiting the enzyme through NADPH-dependent reactive intermediates, suggesting potential interactions with medications metabolized by CYP2C9.

==Pharmacology== It enhances the binding activity of the GABA_A receptor. Specifically, at a concentration of 0.1 micromolar, (+)-methysticin increases the binding of the receptor ligand [3H]bicuculline methochloride by approximately 18% to 28%, indicating it acts as a positive modulator of the GABAA receptor. This modulatory effect is similar in strength to related kavapyrones such as (+)-kavain and (+)-dihydromethysticin. Importantly, methysticin's effect is not due to interaction with the benzodiazepine receptor, as it does not influence the binding of [3H]flunitrazepam, which is a benzodiazepine receptor ligand. Structural features, such as the angular lactone ring present in methysticin and other enolides, are crucial for this activity. Overall, methysticin enhances GABA_A receptor function through a mechanism distinct from that of benzodiazepines, contributing to the neuroactive properties of kava.