Abstract: To expand the marine-associated fungal sources of JBIR-99, evaluate its in vitro antitumor activity, and investigate the effects of different culture conditions on its relative accumulation, the Conus litteratus-associated fungus Parengyodontium album HD005 was subjected to solid-state fermentation, followed by the isolation, purification, and structural characterization of JBIR-99. A total of 578.1mg of JBIR-99 was isolated, and its structure and absolute configuration were confirmed by spectroscopic analyses and single-crystal X-ray diffraction. In vitro activity assays showed that JBIR-99 exhibited micromolar antiproliferative activity against the nasopharyngeal carcinoma cell lines CNE1 and CNE2 and the oral squamous cell carcinoma cell line SCC9, while showing weaker cytotoxicity toward the immortalized human keratinocyte cell line HaCaT. The selectivity indices (SI) for CNE1, CNE2, and SCC9 were 8.73, 18.06, and 12.60, respectively, indicating a certain degree of tumor-cell selectivity. Further comparison of the relative accumulation of JBIR-99 under different culture conditions showed that supplementation with 2% yeast extract and 2% corn steep liquor increased its relative accumulation to 2.97- and 2.72-fold that of the basal medium, respectively, indicating favorable effects on JBIR-99 accumulation. These findings expand the marine-associated fungal sources of JBIR-99 and provide additional information on its in vitro antitumor activity, while identifying culture conditions favorable for its relative accumulation, thereby providing an experimental basis for improving JBIR-99 availability and supporting further biological activity studies.

Key words: Fungus isolated from Conus litteratus, Parengyodontium album, JBIR-99, antitumor activity, culture conditions, relative accumulation