ARS | Publication request: Strain of Fusarium oxysporum Isolated From Almond Hulls Produces Styrene and 7-Methyl-1,3,5-Cyclooctatriene as the Principal Volatile Components

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 23, 2008
Publication Date: November 11, 2008
Citation: Beck, J.J., Merrill, G.B., Palumbo, J.D., O Keeffe, T.L. 2008. Strain of Fusarium Oxysporum Isolated From Almond Hulls Produces Styrene and 7-Methyl-1,3,5-Cyclooctatriene as the Principal Volatile Components. Journal of Agricultural and Food Chemistry. 56(23):11392-11398.

Interpretive Summary: Fusarium oxysporum is a ubiquitous fungus, along with several other fungi, found in the orchards of Prunus dulcis (sweet almond). An isolated strain of Fusarium oxysporum from the hulls of Prunus dulcis was found to produce relatively large quantities of the hydrocarbons styrene and two isomers of 7-methyl-1,3,5-cyclooctatriene (MCOT). Production of styrene and MCOT was reproduced on small scale using potato dextrose agar as a growth medium, and scaled up using one liter of inoculated potato dextrose broth. The compounds were trapped as volatile organic compounds (VOCs) onto solid-phase microextraction (SPME) for small scale, Tenax for large scale, identified by gas chromatography/mass spectroscopy (GC-MS), and then isolated using standard high performance liquid chromatography (HPLC) methods. The identity of styrene was verified by comparison to the GC-MS retention times, fragmentation patterns, and calculated retention indices of a commercially available sample. The identity of MCOT was verified by a short chemical synthesis and comparison of spectroscopic data to the original sample. A biosynthetic scheme of styrene is proposed based upon a carbon-13 labeling study. This is the first report of MCOT isolated as a natural product. Two isomers of MCOT were thought to be biogenic, whereas a third isomer was thought to be the result of thermal isomerization of one of the original isomers.

Technical Abstract: An isolated strain of Fusarium oxysporum from the hulls of Prunus dulcis (sweet almond) was found to produce relatively large quantities of the hydrocarbons styrene and three isomers of 7-methyl-1,3,5-cyclooctatriene (MCOT). Production of styrene and MCOT was reproduced on small scale using potato dextrose agar as a growth medium, and scaled up using one liter of inoculated potato dextrose broth. The compounds were trapped as volatiles onto solid-phase microextraction (SPME) for small scale, Tenax for large scale, and then isolated using standard high performance liquid chromatography (HPLC) methods. Styrene was authenticated by comparison to the retention times, fragmentation patterns, and calculated retention indices of a commercially available sample. The identity of MCOT was verified by a short chemical synthesis and comparison of spectroscopic data to the original sample.