Sesquiterpenoids from culture of the fungus Stereum complicatum (Steraceae): Structural diversity, antifungal, and phytotoxic activities

Authors: PERERA, WILMER - Orise Fellow; Meepagala, Kumudini; Wedge, David; Duke, Stephen

Submitted to: Phytochemistry Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2020
Publication Date: 4/25/2020
Citation: Perera, W.H., Meepagala, K.M., Wedge, D.E., Duke, S.O. 2020. Sesquiterpenoids from culture of the fungus Stereum complicatum (Steraceae): Structural diversity, antifungal, and phytotoxic activities. Phytochemistry Letters. 37:51-58. https://doi.org/10.1016/j.phytol.2020.03.012.
DOI: https://doi.org/10.1016/j.phytol.2020.03.012

Interpretive Summary: The diversity of fungal species and their ability to grow in different habitats and media make them an invaluable source of compounds with a wide range of biological activities. Herein, we describe the isolation and identification of four new and three known compounds s from the culture broth of the fungus infecting turnip plants identified as Stereum complicatum. Chemical structures were confirmed by modern spectroscopic methods. These compounds showed antifungal and phytotoxic properties.

Technical Abstract: The diversity of fungal species and their ability to thrive in different habitats or fermentative conditions make them an invaluable source of secondary metabolites with a wide range of biological activities. Herein, we describe the isolation and identification of four new and three known sesquiterpenes from the culture broth of the fungus Stereum complicatum. Chemical structures were elucidated based on High Resolution Direct Analysis-Mass Spectroscopy (HR-DART-MS), 1D and 2D Nuclear Magnetic Resonance (NMR) experiments Double Quantum Filtered Correlation Spectroscopy (DQFCOSY), Homo nuclear Single Quantum Correlating/Heteronuclear-Multiple Quantum Correlation(HSQC/HMQC), Heteronuclear Multiple Bond Correlation (HMBC) and Nuclear Over Hauser Effect Spectroscopy (NOESY). The compounds had hirsutane-, illudane- or sterpurane-type skeletons. Compounds were identified as sterostrein X (1), sterostrein Y (2), hirsutenol G (3), sterpurol C (4), sterostrein H (5), sterostrein P (6) and sterostrein Q (7). The phytotoxicity of 1-7 was assayed against Lactuca sativa, Agrostis stolonifera and Lemna paucicostata. Compounds showed slight or no activity against L. sativa, whereas the illudane-type sesquiterpenes 5 and 6 were the most active compounds against A. stolonifera. Moreover, 5 was the only compound that was phytotoxic to L. paucicostata, with an IC50 value of 46.2 µM. The antifungal activity of the purified compounds was also evaluated against five plant pathogenic fungi. Compounds 2 and 5 slightly inhibited growth of B. cinerea and C. fragariae at 100 mM and C. acutatum at 50 mM, while 5 inhibited the growth of C. acutatum at 20 mM.