| Summary: | Puniceusines A–N (<b>1</b>–<b>14</b>), 14 new isoquinoline alkaloids, were isolated from the extracts of a deep-sea-derived fungus, <i>Aspergillus puniceus</i> SCSIO z021. Their structures were elucidated by spectroscopic analyses. The absolute configuration of <b>9</b> was determined by ECD calculations, and the structures of <b>6</b> and <b>12</b> were further confirmed by a single-crystal X-ray diffraction analysis. Compounds <b>3</b>–<b>5</b> and <b>8</b>–<b>13</b> unprecedentedly contained an isoquinolinyl, a polysubstituted benzyl or a pyronyl at position C-7 of isoquinoline nucleus. Compounds <b>3</b> and <b>4</b> showed selective inhibitory activity against protein tyrosine phosphatase CD45 with IC<sub>50</sub> values of 8.4 and 5.6 µM, respectively, <b>4</b> also had a moderate cytotoxicity towards human lung adenocarcinoma cell line H1975 with an IC<sub>50</sub> value of 11.0 µM, and <b>14</b>, which contained an active center, -C=N<sup>+</sup>, exhibited antibacterial activity. An analysis of the relationship between the structures, enzyme inhibitory activity and cytotoxicity of <b>1</b>–<b>14</b> revealed that the substituents at C-7 of the isoquinoline nucleus could greatly affect their bioactivity.
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