Planta Med 2019; 85(14/15): 1136-1142
DOI: 10.1055/a-1008-9491
Biological and Pharmacological Activity
Original Papers
Georg Thieme Verlag KG Stuttgart · New York

Monoamine Oxidase Inhibition by Kavalactones from Kava (Piper Methysticum)

Denise Prinsloo
Pharmaceutical Chemistry, School of Pharmacy and Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom, South Africa
Sandra van Dyk
Pharmaceutical Chemistry, School of Pharmacy and Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom, South Africa
Anél Petzer
Pharmaceutical Chemistry, School of Pharmacy and Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom, South Africa
Jacobus P. Petzer
Pharmaceutical Chemistry, School of Pharmacy and Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom, South Africa
› Author Affiliations
Further Information

Publication History

received 29 January 2019
revised 13 August 2019

accepted 01 September 2019

Publication Date:
20 September 2019 (online)


Monoamine oxidases (MAOs) are key metabolic enzymes for neurotransmitter and dietary amines and are targets for the treatment of neuropsychiatric and neurodegenerative disorders. This study examined the MAO inhibition potential of kavain and other kavalactones from the roots of kava (Piper methysticum), a plant that has been used for its anxiolytic properties. (±)-Kavain was found to be a good potency in vitro inhibitor of human MAO-B with an IC50 of 5.34 µM. (±)-Kavain is a weaker MAO-A inhibitor with an IC50 of 19.0 µM. Under the same experimental conditions, the reference MAO inhibitor, curcumin, displays IC50 values of 5.01 µM and 2.55 µM for the inhibition of MAO-A and MAO-B, respectively. It was further established that (±)-kavain interacts reversibly and competitively with MAO-A and MAO-B with enzyme-inhibitor dissociation constants (Ki) of 7.72 and 5.10 µM, respectively. Curcumin in turn, displays a Ki value of 3.08 µM for the inhibition of MAO-A. Based on these findings, other kavalactones (dihydrokavain, methysticin, dihydromethysticin, yangonin, and desmethoxyyangonin) were also evaluated as MAO inhibitors in this study. Yangonin proved to be the most potent MAO inhibitor with IC50 values of 1.29 and 0.085 µM for MAO-A and MAO-B, respectively. It may be concluded that some of the central effects (e.g., anxiolytic) of kava may be mediated by MAO inhibition.

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