Biotransformation of 6-Pentyl-2-pyrone by Botrytis cinerea in Liquid Cultures

Metabolism of 6-pentyl-2-pyrone (6PP) added at rates up to 120 μg/mL to liquid Botrytis cinerea cultures produced the previously unreported compounds 3-(2-pyron-6-yl)propanoic acid and 5-(2-pyron-6-yl)pentanoic acid. Another metabolite was identified tentatively from its mass spectrum as either 5-(2-pyron-6-yl)pentanol or 5-(2-pyron-6-yl)pentan-2-ol. B. cinerea hyphae remained viable with 6PP at 200 μg/mL, but their growth was suppressed at this concentration. Pyrone-containing metabolites were not observed in all systems to which 6PP had been added, but were formed in both hyphal development and sporulating phases of growth. These metabolites were stable in the presence of actively growing B. cinerea cultures and did not appear to alter fungal growth. It is proposed that the changes to the alkyl side chain in the metabolites reduced their lipophilicity and ability to permeate cell membranes relative to the parent compound, thus reducing their toxicity to the fungus.