目的 利用阿达青霉对熊果酸进行微生物转化研究。方法 将熊果酸投入阿达青霉液体培养基中，28 ℃、140 r/min条件下共培养5 d后超声处理，正丁醇萃取获得富集的转化产物提取物；利用多种柱色谱方法分离转化产物，通过核磁共振波谱技术（¹H-NMR、¹³C-NMR、DEPT、HMQC、HMBC、NOESY），结合理化常数和化学反应等方法鉴定化合物的结构；利用MTT法测定了转化产物和底物对HepG2细胞的细胞毒活性。结果 获得了一个熊果酸的微生物转化产物，其结构鉴定为3β, 21α-二羟基熊果酸-28-O-β-D-葡萄糖苷，该转化产物具有一定的抑制HepG2肿瘤细胞的细胞毒活性，其IC₅₀为19.72 μmol/L。结论 转化产物3β, 21α-二羟基熊果酸-28-O-β-D-葡萄糖苷为1个新化合物，其对HepG2肿瘤细胞的细胞毒活性强于底物。

Objective To study the microbial transformation of ursolic acid by Penicillium adametzi. Methods The biotransformed extract was obtained by co-culture of substrate (ursolic acid) and the transferring fungi in a liquid medium at certain conditions, and then the inocula were dealt in an ultrasonic bath and extracted with n-BuOH. The transformed extract was isolated by chromatography on macroporous resin column, silica gel column, and preparative HPLC. The structures of the isolated compounds were identified by spectral analyses, physical constants, and chemical evidences. Results A microbial transformed product was isolated and identified as 3β, 21α-dihydroxyl-ursolic acid-28-O-β-D-glucopyranoside and it had the significant inhibitory effects against HepG2 cell with IC₅₀ value of 19.72 μmol. Conclusion The transformed product, 3β, 21α-dihydroxyl-ursolic acid-28-O-β-D-glucopyranoside, is a new compound with the stronger cytotoxic activity than that of substrate.