New Bioactive Polyketides from the Mangrove-Derived Fungus Daldinia eschscholzii HJX1P2

Three new naphthalene-chroman dimer derivatives, daldinaphchromes A-C (<b>1</b>-<b>3</b>), two new chroman derivatives, daldichromes A (<b>5</b>) and B (<b>6</b>), along with five known compounds (<b>4</b>, <b>7</b>-<b>10</b>) were isolated from the mangrove-derived fungus <i>Daldinia eschscholzii</i> HJX1P2. Their structures and stereochemistries were elucidated through detailed NMR and MS analyses, calculated electronic circular dichroism, and comparison with previously reported data. Compound <b>1</b> demonstrated inhibitory effects on nitric oxide (NO) production in LPS-induced RAW 264.7 cells, with an IC₅₀ value of 62.9 µM, and more effectively suppressed the expression of interleukin (IL)-6 than dexamethasone. A further mechanistic study suggested that <b>1</b> could prohibit the expression of iNOS in RAW 264.7 cells, and the molecular docking study suggested a possible interaction between <b>1</b> and the iNOS protein. Compounds <b>7</b> and <b>8</b> exhibited moderate to potent DPPH radical scavenging activity, with IC₅₀ values of 117.4 and 46.2 µM, respectively, compared with the positive control ascorbic acid (IC₅₀ = 45.6 µM). Compounds <b>4</b> and <b>10</b> showed ABTS⁺ radical scavenging activity, with IC₅₀ values of 66.6 and 33.2 µM, respectively, which were equal to or lower than that of the positive control vitamin C (IC₅₀ = 59.7 µM). Compounds <b>1</b>-<b>3</b>, <b>7</b>, and <b>9</b> showed antibacterial activity against three <i>Staphylococcus aureus</i> strains, with MIC values of 74.4-390.6 μM.