New anthraquinone derivatives acruciquinones A–C (1–3), together with ten known metabolites, were isolated from the obligate marine fungus Asteromyces cruciatus KMM 4696. Acruciquinone C is the first member of anthraquinone derivatives with a 6/6/5 backbone. The structures of isolated compounds were established based on NMR and MS data. The absolute stereoconfigurations of new acruciquinones A–C were determined using ECD and quantum chemical calculations (TDDFT approach). A plausible biosynthetic pathway of the novel acruciquinone C was proposed. Compounds 1–4 and 6–13 showed a significant antimicrobial effects against Staphylococcus aureus growth, and acruciquinone A (1), dendryol B (4), coniothyrinone B (7), and ω-hydroxypachybasin (9) reduced the activity of a key staphylococcal enzyme, sortase A. Moreover, the compounds, excluding 4, inhibited urease activity. We studied the effects of anthraquinones 1, 4, 7, and 9 and coniothyrinone D (6) in an in vitro model of skin infection when HaCaT keratinocytes were cocultivated with S. aureus. Anthraquinones significantly reduce the negative impact of S. aureus on the viability, migration, and proliferation of infected HaCaT keratinocytes, and acruciquinone A (1) revealed the most pronounced effect.

The marine fungal strain KMM 4719 was isolated from the sea cucumber Apostichopus japonicus and identified as Penicillium polonicum based on three molecular genetic markers: ITS, BenA, and CaM. 3-O-methylviridicatin was isolated from the ethyl acetate extract of the strain culture. 3-O-methylviridicatin has demonstrated cardioprotective activity for the first time, as well as urease inhibitory activity (IC₅₀ 97.3 μM). In addition, 3-O-methylviridicatin at a concentration of 100 μM (25.1 μg/mL) inhibited the growth of the yeast-like fungus Candida albicans at 23.2%.