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

LC-HRMS/MS analysis facilitated the precise targeting, isolation, and identification of unusual dimeric diarylheptanoids from <i>Alpinia officinarum</i> (<i>A. officinarum</i>). The tandem MS data for (4<i>E</i>)-1,7-diphenyl-4-hepten-3-one (<b>7</b>) revealed fragment ions at <i>m</i>/<i>z</i> 91, 105, and 117, which are fragmentation patterns specific to diarylheptanoids. In the tandem MS data, peaks with <i>m</i>/<i>z</i> values ranging from 450 to 600 that exhibited these specific fragment ions were selected and isolated. Consequently, two previously undescribed dimeric diarylheptanoids (<b>1</b> and <b>2</b>) and four unusual diarylheptanoids (<b>3</b>-<b>6</b>) along with 10 monomeric diarylheptanoids (<b>7</b>-<b>16</b>) were isolated from the rhizomes of <i>A. officinarum</i> 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 <b>1</b>, <b>7</b>, and <b>9</b> exhibited remarkable inhibitory effects with IC₅₀ values of 14.7, 6.6, and 5.0 μM, respectively.