Cytotoxic Diketopiperazine Alkaloids and Polyketides Isolated From the Deep-Sea Fungus Subuliphorum sp. SCSIO 41053

Fermentation of the deep-sea fungus Subuliphorum sp. SCSIO 41053 on rice medium yielded two novel metabolites, aspergiamide G (1) and palitantin D (6), along with 12 previously reported compounds (2-5 and 7-14). Comprehensive spectroscopic analyses, including nuclear magnetic resonance, mass spectrometry, and electronic circular dichroism, were used to establish the chemical structures and stereochemistry, which were corroborated by literature comparison. Biological evaluation revealed that compounds 4, 6, and 9 exhibited moderate cytotoxicity against the mouse melanoma cell line (B16F10), with half-maximal inhibitory concentration values of 10.07 ± 1.68, 10.93 ± 5.60, and 30.00 ± 7.33 µM, respectively. Molecular docking studies suggested that compounds 4 and 6 interact strongly with the active site of tyrosinase, a key enzyme in melanogenesis, highlighting their potential as enzyme inhibitors.