Abstract
AbstractCycloastragenol is a cycloartane‐type triterpenoid with significant telomerase‐activating activities. In this paper, the biocatalysis of cycloastragenol by two strains of filamentous fungi, namely Syncephalastrum racemosum AS 3.264 and Alternaria alternata AS 3.4578, was investigated. Scaled‐up biotransformation reactions yielded 27 metabolites. Their structures were established on the basis of extensive NMR and HR‐ESI‐MS data analyses, and 18 of them are new compounds. The two fungal strains exhibited distinct biocatalytic features. S. racemosum could catalyze ring expansion and epoxidation reactions to form 3β,10β‐epoxy‐ or 6α,19α‐epoxy‐9,10‐seco‐cycloartane structures, whereas A. alternata preferred to catalyze acetylation reactions, especially at 3‐OH, 6‐OH and 19‐OH. These regio‐ and stereoselective reactions are difficult to achieve by chemical means, but could be realized under mild conditions by biocatalysis. Furthermore, we found that some acetylated derivatives at 50 μM could significantly extend the lifespan of Caenorhabditis elegans from 16.93±0.70 d of the control group to 20.01±0.75 d (P<0.01), versus 18.54±0.67 d for cycloastragenol. These biotransformed derivatives of cycloastragenol could be potential anti‐aging agents.magnified image
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