Isolation and Identification of Constituents Exhibiting Antioxidant, Antibacterial, and Antihyperuricemia Activities in Piper methysticum Root

The aqueous extract of kava ( ) root is known as a traditional beverage for daily intake in the Western Pacific Islands, such as Fiji, Tonga, and Vanuatu, to induce relaxation and health-beneficial effects. In this study, the antioxidant, anti-hyperuricemia, and antibacterial properties of kava root were investigated through the isolation and purification of bioactive compounds in ten fractions separated by column chromatography (CC). They included six flavonoids, 5-hydroxy-4',7-dimethoxyflavanone ( ), matteucinol ( ), isosakuranetin ( ), 5,7- dimethoxyflavanone ( ), 2',4'-dihydroxy-6'-methoxydihydrochalcone (in ) and alpinetin ( ), and seven kavalactones, 5,6-dehydrokawain (DK) (in and ), kavain (in ), yangonin (in and ), dihydro-5,6-dehydrokavain (DDK) (in ), 7,8-dihydromethysticin (in ), dihydromethysticin (in ), methysticin (in ). The chemical structures of the compounds were illustrated by the analyses of gas chromatography-mass spectrometry (GC-MS), electrospray ionization-mass spectrometry (ESI-MS), nuclear magnetic resonance ( H and C-NMR), and X-ray diffraction. The evaluation of the free radical scavenging activity of the isolated substances via the DPPH and ABTS assays revealed that (IC : ABTS = 76.5; DPPH = 74.8 µg/mL) possessed the strongest antioxidant property. In terms of anti-hyperuricemia activity evaluated via the xanthine oxidase inhibitory in vitro assay, the compound was the most promising inhibitor, revealing an IC of 134.52 µg/mL. The two kavalactone mixtures in and a pure compound inhibited the growth of bacteria , while can constrain the development of This is the first study to isolate, purify, and identify the flavonoids isosakuranetin, 2',4'-dihydroxy-6'-methoxydihydrochalcone and alpinetin in kava root and report their pharmaceutical potential. The identified bioactive compounds showed potent antioxidant, anti-hyperuricemia, and antibacterial activity and thus can enhance the value of beverages and foods derived from kava root.