Find in Library

The aqueous extract of kava (<i>Piper methysticum</i>) 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 (<b>C1</b>), matteucinol (<b>C2</b>), isosakuranetin (<b>C3</b>), 5,7- dimethoxyflavanone (<b>C4</b>), 2′,4′-dihydroxy-6′-methoxydihydrochalcone (in <b>MC5</b>) and alpinetin (<b>C10</b>), and seven kavalactones, 5,6-dehydrokawain (DK) (in <b>MC5</b> and <b>C6</b>), kavain (in <b>MC7</b>), yangonin (in <b>MC7</b> and <b>C8</b>), dihydro-5,6-dehydrokavain (DDK) (in <b>MC9</b>), 7,8-dihydromethysticin (in <b>MC9</b>), dihydromethysticin (in <b>MC9</b>), methysticin (in <b>MC9</b>). 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 (¹H and ¹³C-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 <b>C3</b> (IC₅₀: 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 <b>C10</b> was the most promising inhibitor, revealing an IC₅₀ of 134.52 µg/mL. The two kavalactone mixtures in <b>MC5</b> and a pure compound <b>C6</b> inhibited the growth of bacteria <i>Listeria monocytogenes</i>, while <b>MC7</b> can constrain the development of <i>Klebsiella pneumoniae.</i> 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.