Microbial transformation of geraniol and nerol by Botrytis cinerea

Summary Biotransformation of geraniol 1A and nerol 1B was studied with four strains of Botrytis cinerea and three growth media. Using grape must predominant conversion of 1A/1B to E-3,7-dimethyl-2-octen-1,8-diol 5 and 2Z,6E-3,7-dimethyl-2,6-octadien-1,8-diol 16B was observed. However, with one strain and 1A, E-2-methyl-2-hepten-6-one-1-ol 2B, 7-hydroxy-6-methyl-2-heptanone 3 and p-menth-1-ene-9-ol 7 were identified as major metabolites. As further fungal bioconversion products of 1A/1B were detected: Z-2-methyl-2-hepten-6-one-1-ol 2A, 2E,6Z-, 2E,6E-and 2Z,6Z-3,7-dimethyl-2,6-octadien-1,8-diol 4A/4B/16A, Z-3,7-dimethyl-2-octen-1,8-diol 17, 3,7-dimethyl-1,8-octandiol 6, 2E,6E-8-hydroxy-2,6-dimethyl-2,6-octadienal 8, geranial and neral 9, 18, citronellol 10, Z- and E-2,6-dimethyl-2,7-octadien-1,6-diol 13A/13B, 6-hydroxy-2,6-dimethyl-2,7-octadienal 14 as well as 2,6-dimethyl-7-octen-1,6-diol 15. Using synthetic growth medium again -hydroxylation reactions were observed, but 2-methyl-2-hepten-6-one 11 and 7 were also identified as major bioconversion products of 1A and 1B, respectively. Additionally, 2-methyl-2-hepten-6-ol 12 was detected and, using 1B, also traces of 2Z,6E-8-hydroxy-2,6-dimethyl-2,6-octadienal 19 and two 3,9-epoxy-p-menth-1-ene isomers 20A/20B were found. Addition of small amounts of grape must to the synthetic medium (1:700 to 5:700) influenced both the yields of metabolites and their qualitative and quantitative distribution. Identifications of biotransformation products of 1A/1B were performed by capillary gas chromatography (HRGC) and coupled HRGC techniques, i.2. on-line-mass spectrometry (HRGC-MS) and-Fourier transform infrared spectroscopy (HRGC-FTIR) after extractive sample preparation.