Anti-inflammatory kavalactones from Alpinia zerumbet

Alpinia zerumbet (Pers.) B.L.Burtt & R.M.Sm. (Zingiberaceae) is a perennial plant native to the East Indies and is widely distributed in South America, Oceania, and Asia. The mature fruits of the plant have been used in traditional medicine in China. In this study, we compared the chemical constituents in the methanol extracts of the leaves, the placenta, the pericarps, and the seeds obtained from the same plant using LC-MS, and we examined the NO inhibitory activities of the respective extracts and the isolated compounds. As a result of LC-MS analyses, kavalactone derivatives (1-6) were detected in the methanol extracts of the leaves, placenta, and pericarps. Of these, compound 6 was identified as a new asymmetrical cyclobutane dimer of 5,6-dehydrokawain. Quantitative analysis showed that the total amounts of kavalactone derivatives were highest in the methanol extract of the pericarps. Moreover, the results of measurements of the anti-inflammatory activity revealed that the pericarps extract showed the strongest activity. The compounds responsible for the anti-inflammatory activity of the extracts from A. zerumbet were identified. Of these, five were known kavalactone derivatives and one was a new kavalactone derivative (aniba dimer C). The results showed that the pericarps of A. zerumbet are a rich source of kavalactone derivatives, and that the pericarps of A. zerumbet can be utilized as an important medicinal resource.