Assessment of Neolignan Profiles during the Growth Period of <i>Magnolia fargesii</i> Leaves and Their MUC5AC Inhibition Potential

The flower buds of <i>Magnolia fargesii</i> (Xinyi) have traditionally been used to treat inflammatory respiratory diseases, including chronic obstructive pulmonary disease (COPD). While previous studies identified seven lignans in Magnolia that alleviate airway inflammation by inhibiting epidermal growth factor receptor (EGFR) activation, the chemical composition and biological activity of the leaves especially at different growth stages remain understudied. In this study, the relationship between neolignan content, anti-inflammatory activity, and mucin 5AC (MUC5AC) expression inhibition in <i>M. fargesii</i> leaves collected from May to July was investigted. Optimal extraction conditions were established using 80% ethanol (EtOH) at 40 °C for 2 h. Metabolite profiling was performed using ultraperformance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS), followed by multivariate statistical analyses including principal component analysis (PCA), orthogonal partial least-squares-discriminant analysis (OPLS-DA), and <i>S</i>-plots. Eight neolignan compounds were identified and structurally confirmed through nuclear magnetic resonance (NMR), circular dichroism (CD) spectroscopy, and mass spectrometry (MS). Quantitative analysis revealed notable variations in metabolite content and bioactivity depending on the collection time. Notably, compounds <b>2</b>, <b>5</b>, and <b>6</b> increased by 1.3-1.4 fold in July compared with June (mg/g, DW), consistent with the enhanced anti-inflammatory and MUC5AC inhibitory effects observed during this period. In contrast, compounds <b>4</b>, <b>7</b>, and <b>8</b> peaked in June and then declined.