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 IC₅₀ values of 14.7, 6.6, and 5.0 μM, respectively.