A new cytochalasin dimer, verruculoid A (1), three new cytochalasin derivatives, including 12-nor-cytochalasin F (2), 22-methoxycytochalasin B6 (3), and 19-hydroxycytochalasin B (4), and 20-deoxycytochalasin B (5), a synthetic product obtained as a natural product for the first time, together with four known analogues (6–9), were isolated and identified from the culture extract of Curvularia verruculosa CS-129, an endozoic fungus obtained from the inner fresh tissue of the deep-sea squat lobster Shinkaia crosnieri, which was collected from the cold seep area of the South China Sea. Structurally, verruculoid A (1) represents the first cytochalasin homodimer containing a thioether bridge, while 12-nor-cytochalasin F (2) is the first 12-nor-cytochalasin derivative. Their structures were elucidated by detailed interpretation of the NMR spectroscopic and mass spectrometric data. X-ray crystallographic analysis and ECD calculations confirmed their structures and absolute configurations. Compound 1 displayed activity against the human pathogenic bacterium Escherichia coli (MIC = 2 μg/mL), while compounds 4, 8, and 9 showed cytotoxicity against three tumor cell lines (HCT-116, HepG-2, and MCF-7) with IC50 values from 5.2 to 12 μM. The structure–activity relationship was briefly discussed.

Ten new tanzawaic acids, namely, steckwaic acids A–D (1–4), 11-ketotanzawaic acid D (5), 6,15-dihydroxytanzawaic acid M (6), 15R-methoxytanzawaic acid M (7), 15S-methoxytanzawaic acid M (8), 8-hydroxytanzawaic acid M (9), and 8-hydroxytanzawaic acid B (10), together with four known analogues (11–14), were isolated and identified from the endozoic fungus Penicillium steckii AS-324, which was obtained from a deep-sea Acanthogorgiidae sp. coral that was collected from the Magellan seamount in the Western Pacific Ocean. Structurally, steckwaic acids A–D (1–4) represent the first tanzawaic acid derivatives containing a naphthalene ring. Their structures were elucidated by detailed interpretation of the NMR spectroscopic and mass spectrometric data. X-ray crystallographic analysis and ECD calculations confirmed their structures and absolute configurations. New compounds 1, 5, and 9 exhibited activities against aquatic pathogenic bacteria Micrococcus luteus, Vibrio anguillarum, and Pseudomonas aeruginosa with MICs of 2, 4, and 4 μg/mL, respectively.