LC/MS guided discovery of new kavalactone derivatives in the pericarps of Alpinia zerumbet

An LC/MS guided phytochemical investigation of the pericarps of Alpinia zerumbet yielded five new kavalactone derivatives (1, 4, 5, 21, and 22) along with some known compounds. These comprised two new kavalactone-monoterpene conjugates possessing tricyclic α-pyrone or bicyclic α-pyrone scaffolds and three new hydroxylated kavalactones. Their structures were elucidated by comprehensive spectroscopic analyses (HRESIMS and 1D/2D NMR) and TD-DFT ECD calculations. Moreover, the absolute configuration of the previously described zerumin E4 (18) was revised. Plausible biosynthetic pathways are proposed to rationalize the oxidative derivatization of kavalactone scaffolds and the limited diastereomeric outcomes observed in the kavalactone-monoterpene conjugates. The present findings expand the current knowledge of chemical diversity of the pericarps and provide insights into the phytochemical basis underlying the medicinal use of A. zerumbet fruits.