Anteaglonialides A-F and Palmarumycins CE₁-CE₃ from Anteaglonium sp. FL0768, a Fungal Endophyte of the Spikemoss Selaginella arenicola

Anteaglonialides A-F (1-6), bearing a spiro[6-(tetrahydro-7-furanyl)cyclohexane-1,2′-naphtho[1,8-de][1,3]-dioxin]-10-one skeleton, three new spirobisnaphthalenes, palmarumycins CE₁-CE₃ (7-9), nine known palmarumycin analogues, palmarumycins CP₅ (10), CP_4a (11), CP₃ (12), CP₁₇ (13), CP₂ (14), and CP₁ (15), CJ-12,371 (16), 4-O-methyl CJ-12,371 (17), and CP₄ (18), together with a possible artifact, 4a(5)-anhydropalmarumycin CE₂ (8a), and four known metabolites, O-methylherbarin (19), herbarin (20), herbaridine B (21), and hyalopyrone (22), were encountered in a cytotoxic extract of a potato dextrose agar culture of Anteaglonium sp. FL0768, an endophytic fungus of the sand spikemoss, Selaginella arenicola. The planar structures and relative configurations of the new metabolites 1-9 were elucidated by analysis of extensive spectroscopic data, and the absolute configuration of 1 was determined by the modified Mosher's ester method. Application of the modified Mosher's ester method combined with the NOESY data resulted in revision of the absolute configuration previously proposed for 10. Co-occurrence of 1-6 and 7-18 in this fungus led to the proposal that the anteagloniolides may be biogenetically derived from palmarumycins. Among the metabolites encountered, anteaglonialide F (6) and known palmarumycins CP₃ (12) and CP₁ (15) exhibited strong cytotoxic activity against the human Ewing's sarcoma cell line CHP-100, with IC₅₀ values of 1.4, 0.5, and 1.6 μM, respectively.