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B-norsteroids from Hymenoscyphus pseudoalbidus
Pierre F Andersson1, Stina Bengtsson, Jan Stenlid
1Department of Chemistry, Uppsala BioCenter, Swedish University of Agricultural Sciences, P.O. Box 7015, Uppsala SE-75007, Sweden.
Molecules (Basel, Switzerland)
|June 27, 2012
Summary
Researchers isolated novel B-norsteroids from the ash dieback fungus Hymenoscyphus pseudoalbidus. These compounds feature unique carbon skeletons and provide insights into fungal-derived steroid biosynthesis and degradation pathways.
Area of Science:
- Mycology
- Natural Products Chemistry
- Organic Chemistry
Background:
- Ash dieback disease is caused by the fungus Hymenoscyphus pseudoalbidus.
- Fungal secondary metabolites, including steroids, can possess unique chemical structures and biological activities.
- Understanding the chemical diversity of fungal compounds is crucial for discovering new bioactive molecules.
Purpose of the Study:
- To isolate and characterize novel B-norsteroids from Hymenoscyphus pseudoalbidus.
- To elucidate the structures and potential biosynthetic pathways of these unique compounds.
- To investigate the chemical transformations and degradation products of the isolated steroids.
Main Methods:
- Liquid culture of Hymenoscyphus pseudoalbidus.
- Isolation and purification of secondary metabolites.
- Structure elucidation using NMR spectroscopy (¹H, ¹³C, HMBC) and LC-HRMS.
- Polarimetry for stereochemical analysis.
Main Results:
- Two novel B-norsteroids, B-norviridiol lactone (1) and B-norviridin enol (2), with unprecedented carbon skeletons were isolated.
- Compound 2 degraded to a third B-norsteroidal compound, 1β-hydroxy-2α-hydro-asterogynin A (3).
- Compound 1's structure was identical to a previously misassigned compound, viridiol.
- An intramolecular hydrogen bond in compound 2 was evidenced by an unprecedented HMBC correlation.
- The B-ring formation in compounds 1-3 was proposed to occur via a benzilic acid rearrangement.
- The known compound asterogynin A was formed from compound 3 by a β-elimination of water.
Conclusions:
- The study identified novel B-norsteroids from H. pseudoalbidus, expanding the known chemical diversity of fungal metabolites.
- The findings provide insights into the structural novelty and potential biosynthetic pathways of B-norsteroids.
- The characterized compounds and their transformations offer a basis for further investigation into their biological activities and ecological roles.
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