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

Truong Ngoc Minh; Truong Mai Van; Tran Dang Khanh; Tran Dang Xuan

doi:10.3390/foods11233889

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

Foods. 2022 Dec 1;11(23):3889. doi: 10.3390/foods11233889.

Authors

Truong Ngoc Minh¹, Truong Mai Van², Tran Dang Khanh^{3

4}, Tran Dang Xuan^{2

5}

Affiliations

¹ Center for Research and Technology Transfer, Vietnam Academy of Science and Technology (VAST), Hanoi 122100, Vietnam.
² Transdisciplinary Science and Engineering Program, Graduate School of Advanced Science and Engineering, Hiroshima University, Hiroshima 739-8529, Japan.
³ Agricultural Genetic Institute, Pham Van Dong Street, Hanoi 122000, Vietnam.
⁴ Center for Agricultural Innovation, Vietnam National University of Agriculture, Hanoi 131000, Vietnam.
⁵ Center for the Planetary Health and Innovation Science (PHIS), The IDEC Institute, Hiroshima University, Higashi-Hiroshima 739-8529, Japan.

Abstract

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

Keywords: Piper methysticum L.; antibacterial activity; antioxidant activity; beverage; flavonoid; kavalactone.

Grants and funding

This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 104.01-2019.316.