This high purity, odd numbered, long-chain fatty acid methyl ester is uncommon in most biological systems and is therefore often useful as an internal standard or biomarker.{50519} Pentadecanoic acid is present naturally in bovine milk where it is produced by bacteria in the rumen and it is useful as a biomarker for milk fat consumption.{29188} It is also present in some bacteria and fungi and in trace amounts in some plant oils.
