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Cycloastragenol is ac ycloartane-type triterpenoid with significant telomerase-activating activities.Inthis paper, the biocatalysisofc ycloastragenol 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 extensiveN MR and HR-ESI-MS data analyses,a nd 18 of them are new compounds.T he twof ungal strains exhibited distinct biocatalytic features. S. racemosum could catalyzer ing expansion ande poxidation reactions to form 3b,10b-epoxy-o r6 a ,19a-epoxy-9,10-seco-cycloartane structures,w hereas A. alternata preferredt oc atalyzea cetylation reactions,e specially at 3-OH, 6-OH and1 9-OH. These regio-ands tereoselective reactions are difficult to achieve by chemical means,b ut could be realized under mild conditions by biocatalysis.F urthermore,w ef ound that some acetylated derivatives at 50 mMc ould significantly extend the lifespan of Caenorhabditise legans from 16.93 AE 0.70 do ft he control group to 20.01 AE 0.75 d (P < 0.01), versus 18.54 AE 0.67 df or cycloastragenol. These biotransformed derivatives of cycloastragenol could be potential anti-aginga gents.

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