The microbial transformation of cycloastragenol (CA) by Mucor racemosus AS 3.20 was investigated. Seven isolated products were identified as (20R,24S)-3β,6α,16β,25- tetrahydroxy-20,24-epoxy-9,10-seco-cycloartan-9(11),10(19)-diene (1), (20R,24S)- 3β,6α,16β,25-tetrahydroxy-20,24-epoxy-9,10-seco-cycloartan-1(10),9(11)-diene (2), (20R,24S)-3β,16β,25-trihydroxy-6α,19α;20,24-diepoxy-9,10-seco-cycloartan-9(11)-ene (3), (20R,24S)-6α,16β,25-trihydroxy-3β,10β;20,24-diepoxy-9,10-seco- cycloartan-11-one (4), (20R,24S)-16β,25-dihydroxy-6α-methoxy-3β,10β;20,24- diepoxy-9,10-seco-cycloartan-7(8),9(11)-diene (5), (20R,24S)-6α,16β,25-trihydroxy-3β,10β;20,24-diepoxy-9,10-seco-cycloartan-9(11)-ene (6), and (20R,24S)-3β,6α,16β,25-tetrahydroxy-19-acetoxy-ranunculan-9(10)-ene (7) by spectroscopic analysis. Among them, compounds 2 and 5 were new compounds. M. racemosus could catalyze ring expansion and epoxidation reactions to form 3β,10β-epoxy- or 6α,19α-epoxy-9,10-seco-cycloartane structures. These regio- and stereo-selective reactions are difficult to achieve by chemical means. In addition, the biological effects of isolated metabolites on increasing the lifespan of Caenorhabditis elegans were evaluated. Most of the metabolites could significantly extend the lifespan of C. elegans at 50 μM.
Keywords: Anti-aging; Biotransformation; Cycloastragenol; Mucor racemosus.