| Summary: | An undescribed hybrid phenalenone dimer, talaropinophilone (<b>3</b>), an unreported azaphilone, 7-<i>epi</i>-pinazaphilone B (<b>4</b>), an unreported phthalide dimer, talaropinophilide (<b>6</b>), and an undescribed 9<i>R</i>,15<i>S</i>-dihydroxy-ergosta-4,6,8 (14)-tetraen-3-one (<b>7</b>) were isolated together with the previously reported bacillisporins A (<b>1</b>) and B (<b>2</b>), an azaphilone derivative, Sch 1385568 (<b>5</b>), 1-deoxyrubralactone (<b>8</b>), acetylquestinol (<b>9</b>), piniterpenoid D (<b>10</b>) and 3,5-dihydroxy-4-methylphthalaldehydic acid (<b>11</b>) from the ethyl acetate extract of the culture of a marine sponge-derived fungus, <i>Talaromyces pinophilus</i> KUFA 1767. The structures of the undescribed compounds were elucidated by 1D and 2D NMR as well as high-resolution mass spectral analyses. The absolute configuration of C-9′ of <b>1</b> and <b>2</b> was revised to be 9′<i>S</i> using the coupling constant value between C-8′ and C-9′ and was confirmed by ROESY correlations in the case of <b>2</b>. The absolute configurations of the stereogenic carbons in <b>7</b> and <b>8</b> were established by X-ray crystallographic analysis. Compounds <b>1</b>,<b>2</b>, <b>4</b>–<b>8</b>, <b>10</b> and <b>11</b> were tested for antibacterial activity against four reference strains, viz. two Gram-positive (<i>Staphylococcus aureus</i> ATCC 29213, <i>Enterococcus faecalis</i> ATCC 29212) and two Gram-negative (<i>Escherichia coli</i> ATCC 25922, <i>Pseudomonas aeruginosa</i> ATCC 27853), as well as three multidrug-resistant strains, viz. an extended-spectrum β-lactamase (ESBL)-producing <i>E. coli</i>, a methicillin-resistant <i>S. aureus</i> (MRSA) and a vancomycin-resistant <i>E. faecalis</i> (VRE). However, only <b>1</b> and <b>2</b> exhibited significant antibacterial activity against both <i>S. aureus</i> ATCC 29213 and MRSA. Moreover, <b>1</b> and <b>2</b> also significantly inhibited biofilm formation in <i>S. aureus</i> ATCC 29213 at both MIC and 2xMIC concentrations.
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