LC-HRMS/MS-Guided Isolation of Unusual Diarylheptanoids from the Rhizomes of Alpinia officinarum

Abstract

LC-HRMS/MS analysis facilitated the precise targeting, isolation, and identification of unusual dimeric diarylheptanoids from Alpinia officinarum (A. officinarum). The tandem MS data for (4E)-1,7-diphenyl-4-hepten-3-one (7) revealed fragment ions at m/z 91, 105, and 117, which are fragmentation patterns specific to diarylheptanoids. In the tandem MS data, peaks with m/z values ranging from 450 to 600 that exhibited these specific fragment ions were selected and isolated. Consequently, two previously undescribed dimeric diarylheptanoids (1 and 2) and four unusual diarylheptanoids (3−6) along with 10 monomeric diarylheptanoids (7−16) were isolated from the rhizomes of A. officinarum using various chromatographic techniques. The structures of the isolates were elucidated by an analysis of 1D/2D NMR and HRESIMS data, and a combination of DP4+ probability analysis and ECD calculations. To evaluate the anti-inflammatory effects of the isolated compounds, their inhibitory activity against nitric oxide production in LPS-induced RAW 264.7 cells was assessed. Compounds 1, 7, and 9 exhibited remarkable inhibitory effects with IC 50 values of 14.7, 6.6, and 5.0 μM, respectively.