Data_Sheet_1_Furanoids from the Gymnadenia conopsea (Orchidaceae) seed germination supporting fungus Ceratobasidium sp. (GS2).docx

Five furanoids including a new analog (S)-1,4-di(furan-2-yl)-2-hydroxybutane-1,4-dione (1) together with four known ones, rhizosolaniol (2), 5-hydroxymethylfurfural (3), 2-furoic acid (4) and (2-furyl) oxoacetamide (5), were isolated from the fungal strain Ceratobasidium sp. (GS2) inducing seed germination of the endangered medicinal plant Gymnadenia conopsea of Orchidaceae. The structure of new furanoid 1 was determined mainly based on HR-ESI-MS and NMR spectral data. Modified Mosher’s reactions were used to establish the stereochemistry of the hydroxyl group in 1, which was not stable in Mosher’s reagents and transformed into four analogs 6–9. These degraded products (6–9) were elucidated based on UPLC-Q-TOF-MS/MS analysis, and compound 8 was further isolated from the degraded mixture and its structure was characterized through NMR experiments. Therefore, the absolute configuration of compound 1 was determined by electronic circular dichroism combined with quantum-chemical calculations adopting time-dependent density functional theory. Compounds (1–5), and 8 showed weak antioxidant activities, and compounds (2–4) displayed phytotoxicity on punctured detached green foxtail leaves. In addition, compounds 3 and 4 strongly showed inhibition activities on the seed germination of G. conopsea. This was the first chemical investigation of the symbiotic fungus of G. conopsea.

本研究从诱导濒危兰科药用植物手参（Gymnadenia conopsea）种子萌发的角担菌属（Ceratobasidium sp.）菌株GS2中，分离得到5个呋喃类化合物（furanoid），其中1个为新类似物：(S)-1,4-二(呋喃-2-基)-2-羟基丁烷-1,4-二酮(1)，其余4个为已知化合物：根毛孢醇（rhizosolaniol，2）、5-羟甲基糠醛（5-hydroxymethylfurfural，3）、2-呋喃甲酸（2-furoic acid，4）以及(2-呋喃基)氧代乙酰胺（(2-furyl) oxoacetamide，5）。新呋喃类化合物1的结构主要通过高分辨电喷雾电离质谱（HR-ESI-MS）与核磁共振波谱（NMR）谱学数据得以确定。为确定化合物1中羟基的立体构型，本研究采用改良莫斯耶反应（Modified Mosher’s reactions）进行解析，但该羟基在莫斯耶试剂中并不稳定，可转化为4个降解类似物6~9。通过超高效液相色谱-四极杆-飞行时间串联质谱（UPLC-Q-TOF-MS/MS）分析，对上述降解产物6~9进行了结构推断；其中化合物8进一步从降解混合体系中分离得到，并通过核磁共振实验完成了结构表征。最终，结合电子圆二色谱（electronic circular dichroism）与采用含时密度泛函理论（time-dependent density functional theory）的量子化学计算，确定了化合物1的绝对构型。化合物1~5与8均表现出较弱的抗氧化活性；化合物2~4则对刺破的离体青狗尾草叶片表现出植物毒性。此外，化合物3与4对手参（Gymnadenia conopsea）的种子萌发具有显著的抑制活性。本研究为首次针对兰科手参共生真菌的化学组分研究。