Microbial transformation of cycloastragenol by <i>Penicillium spinulosum</i> AS3.149

Two new metabolites, 29-demethyl-3-ene-cycloastragenol (<b>2</b>) and 1<i>α</i>,12<i>α</i>-dihydroxy-cycloastragenone (<b>3</b>), along with six known compounds (<b>4</b>-<b>9</b>) were obtained from the microbial transformation of cycloastragenol (<b>1</b>) by <i>Penicillium spinulosum</i> AS3.149. The structures of these metabolites were determined by extensive spectroscopic (IR, UV, HRESIMS, 1D and 2D NMR) data analyses. Compound <b>2</b> features a 29-nor-triterpenic skeleton, possibly formed through sequential oxidation, decarboxylation, and dehydration reactions. Biological assays revealed that compound <b>6</b> exhibited significant cytotoxic activity against the K562 cell line with an IC₅₀ value of 1.0 μM.