Spiro-Phthalides and Isocoumarins Isolated from the Marine-Sponge-Derived Fungus Setosphaeria sp. SCSIO41009

Fourteen new polyketides classified as four phthalides, setosphalides A and B, 5-O-desmethyl­colletotrialide, and (S)-colletotrialide (1–4), three isocoumarin derivatives, exserolides I–K (5–7), four pyrones, setosphapyrones A–D (8–11), one furanone (12), and two depsidones (13 and 14), along with 17 known polyketides were isolated from cultures of the sponge-derived fungus Setosphaeria sp. SCSIO41009. The structures and absolute configurations of these new compounds (1–14) were determined by spectroscopic analyses, X-ray diffraction, chiral-phase HPLC analysis, modified Mosher’s method, and comparison of ECD spectra to calculations. Setosphalides A (1) and B (2) are the first examples possessing a 5,5 spiroketal skeleton in phthalide derivatives. Botryorhodines I (13) and J (14) showed moderate antifungal activities against the phytopathogenic fungi Colletotrichum asianum and Colletotrichum acutatum. Compound 18 (7-O-demethylmonocerin) exhibited potent radical scavenging activity against DPPH.

本研究从海绵来源真菌Setosphaeria sp. SCSIO41009的发酵培养液中分离得到14个全新聚酮类（polyketides）化合物，其中包括4个苯酞类（phthalides）化合物：setosphalides A、B、5-O-去甲基毛球壳菌内酯（5-O-desmethylcolletotrialide）与(S)-毛球壳菌内酯（(S)-colletotrialide，编号1~4）；3个异香豆素类（isocoumarin derivatives）衍生物exserolides I~K（编号5~7）；4个吡喃酮类（pyrones）化合物setosphapyrones A~D（编号8~11）；1个呋喃酮类（furanone）化合物（编号12）；以及2个缩酚酸类（depsidones）化合物（编号13、14），此外还分离得到17个已知聚酮类化合物。通过光谱解析、X射线单晶衍射、手性相高效液相色谱（chiral-phase HPLC）分析、改良莫斯利（Mosher）法以及电子圆二色谱（Electronic Circular Dichroism, ECD）谱图与计算结果的比对，确定了这14个全新化合物（1~14）的结构及绝对构型。Setosphalides A（1）与B（2）是苯酞类衍生物中首个拥有5,5-螺环缩酮骨架的化合物。化合物13、14（即Botryorhodines I、J）对植物病原真菌亚洲炭疽菌（Colletotrichum asianum）和尖孢炭疽菌（Colletotrichum acutatum）表现出中等强度的抗真菌活性。化合物18（7-O-去甲基monocerin，7-O-demethylmonocerin）对DPPH自由基展现出强效的自由基清除活性。