| Summary: | Ten polyketide derivatives (<b>1</b>–<b>10</b>), including a new natural product named (<i>E</i>)-2,4-dihydroxy-3-methyl-6-(2-oxopent-3-en-1-yl) benzaldehyde (<b>1</b>), and five known diketopiperazines (<b>11</b>–<b>15</b>), were isolated from the mangrove-sediment-derived fungus <i>Aspergillus</i> sp. SCSIO41407. The structures of <b>1</b>–<b>15</b> were determined via NMR and MS spectroscopic analysis. In a variety of bioactivity screening, <b>3</b> showed weak cytotoxicity against the A549 cell line, and <b>2</b> exhibited weak antibacterial activity against methicillin-resistant <i>Staphylococcus aureus</i> (MRSA). Compounds <b>3</b>, <b>5</b>, and <b>6</b> showed inhibition against acetylcholinesterase (AChE) with IC<sub>50</sub> values of 23.9, 39.9, and 18.6 μM. Compounds <b>11</b>, <b>12</b>, and <b>14</b> exhibited obvious inhibitory activities of lipopolysaccharide (LPS)-induced nuclear factor-<i>κ</i>B (NF-<i>κ</i>B) with IC<sub>50</sub> values of 19.2, 20.9, and 8.7 μM, and they also suppressed RANKL-induced osteoclast differentiation in bone marrow macrophages cells (BMMCs), with the concentration of 5 μM. In silico molecular docking with AChE and NF-<i>κ</i>B p65 protein were also performed to understand the inhibitory activities, and <b>1</b>, <b>11</b>–<b>14</b> showed obvious protein/ligand-binding effects to the NF-κB p65 protein.
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