Natural products and biological activity from fungal symbionts associated with <i>Rosmarinus officinalis L.</i>

An endophytic fungus isolated from the rhizomes of <i>Rosmarinus officinalis</i> was identified as a <i>Talaromyces</i> species. Five distinct compounds were successfully isolated from the crude extract obtained from the fermentation culture, and identified as (1) thymol, (2) phloretin, (3) hesperetin, (4) dihydroquercetin, and (5) 6,7-dihydroxycoumarin. The antimicrobial activities of the five compounds were evaluated against <i>Candida albicans</i>, <i>Escherichia coli</i>, and <i>Staphylococcus aureus</i>, revealing varied efficacy. Compound 2 was the most effective inhibitor of <i>C. albicans</i>. Activity against <i>E. coli</i> was observed for compounds 1, 2, 3, and 5. In the hydroxyl radical (·OH) scavenging assay, all five compounds exhibited weak reducing capacity. In the DPPH radical scavenging and ferric reducing antioxidant power (FRAP) assays, compound 5 exhibited the highest scavenging activity. Additionally, cytotoxicity assays revealed that among the ID8, HeLa, and 293 T cell lines tested, the five compounds exhibited the strongest inhibitory effects against the ID8 cell line.