The stereoselective oxidation of ( − )-isolongifolanol ( 1 ) with a longifolene skeleton by Aspergillus niger (NBRC 4414) as a biocatalyst and suppressive effect on umuC gene expression by chemical mutagens furylfuramid and AFB1 of the SOS response in Salmonella typhimurium TA1535/pSK1002 were investigated. Compound 1 was converted to a new terpenoid, (-)-(2 S, 8 R )-8,12-dihydroxy-isolongifolanol ( 2 ). Its structure was determined by NMR, IR, specifi c rotation and mass spectrometry. The metabolites suppressed the SOS-inducing activity of furylfuramid and AFB 1 in the umu test. Compound 1 suppressed 51% of the SOS-inducing activity against furylfuramid at Ͻ 1.0 mM. Compound 2 suppressed 15% and 24% of the SOS-inducing activity against furylfuramid and AFB1 at Ͻ 1.0 mM respectively.

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