Endophytic fungi were used not only for their producing bioactive products but also for their ability to transform natural compounds. An endophytic fungus, isolated from medicinal plant Huperzia serrata, was identified as Umbelopsis isabellina based on the internal transcribed spacer of ribosomal DNA (rDNA-ITS) region. It was used to transform ursolic acid (1), a pentacyclic triterpene. Incubation of ursolic acid with U. isabellina afforded three products, 3β-hydroxy-urs-11-en-28,13-lactone (2), 3β,7β-dihydroxy-urs-11-en-28,13-lactone (3), 1β,3β-dihydroxy-urs-11-en-28,13-lactone (4). Although product 2 was a known compound, it was first obtained by microbial transformation. Products 3 and 4 were new compounds. The structural elucidation of the three compounds was achieved mainly by the 1D- and 2D-NMR, MS, IR data. The endophytic fungus U. isabellina can hydroxyate the C12–C13 double bond at position 13 of ursolic acid 1 and form a five-member lactone effectively. In the meantime, this fungus can also introduce the hydroxyl group at C-1 or C-7 of ursolic acid 1.
内生真菌不仅能生产
生物活性产品,还能转化天然化合物。根据
核糖体 DNA 内部转录间隔区(rDNA-I
TS),从药用植物 Huperzia serrata 中分离出的内生真菌被鉴定为 Umbelopsis isabellina。它被用来转化
熊果酸(1)--一种五环三萜。将
熊果酸与 U. isabellina 培养可得到三种产物:3β-羟基-熊-11-烯-28,13-内酯(2)、3β,7β-二羟基-熊-11-烯-28,13-内酯(3)、1β,3β-二羟基-熊-11-烯-28,13-内酯(4)。虽然产品 2 是一种已知化合物,但它是通过微
生物转化首次获得的。产物 3 和 4 是新化合物。这三种化合物的结构阐释主要是通过一维和二维 NMR、MS 和 IR 数据实现的。内生真菌 U. isabellina 可以羟化
熊果酸 1 第 13 位的 C12-C13 双键,并有效地形成五元内酯。同时,该真菌还能在
熊果酸 1 的 C-1 或 C-7 位引入羟基。