Biotransformation of Neoruscogenin by the Endophytic Fungus Alternaria eureka

WOS: 000436527100006PubMed ID: 29893560Biotransformation of neoruscogenin (NR, 1, spirosta-5,25(27)-diene-1 beta,3 beta-diol), the major bioactive sapogenin of Ruscus preparations, was carried out with the endophytic fungus Alternaria eureka. Fourteen new biotransformation products (2-15) were isolated, and their structures were elucidated by NMR and HRESIMS data analyses. A. eureka affected mainly oxygenation, oxidation, and epoxidation reactions on the B and C rings of the sapogenin to afford compounds 8-15. In addition to these, cleavage of the spiroketal system as in compounds 2-7 and subsequent transformations provided unusual metabolites. This is the first study reporting conversion of the spirostanol skeleton to cholestane-type metabolites 2-5. Additionally, the cleavage of the C-22/C-26 oxygen bridge yielding a furostanol-type steroidal framework and subsequent formation of the epoxy bridge between C-18 and C-22 in 7 was encountered for the first time in steroid chemistry.Ege University Scientific Research ProjectEge University [15ECZ9011]; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114Z958]This project was supported by Ege University Scientific Research Project 15ECZ9011 and partly by TUBITAK (Project No: 114Z958). We are very grateful to Bionorm Natural Products for providing neoruscogenin, and special thanks to NMR operator Anzarulhaque Anwarulhaque of Prince Sattam bin Abdulaziz University, Al-Kharj, Saudi Arabia