Antimicrobial Activity of Undecan-2-one, Undecan-2-ol and Their Derivatives

The antimicrobial activity of undecan-2-one, its ethylene acetal, racemic mixture and enantiomers of undecan-2-ol, and undec-2-yl acetate, towards bacteria Escherichia coli, Bacillus subtilis, yeast Candida mycoderma and mould Aspergilus niger was investigated. These components are abundantly present in essential oils obtained from various rue species. The essential oil from Ruta chalepensis L. growing in Turkey contains 66.5% undecan-2-one, and that from Ruta Montana L. even 84.2%. Chinese Ruta graveolens L. contains 67.0% of this ketone. Dextrorotatory S-(+)-undecan-2-ol is a component of cocoa butter, and its R-(-)- enantiomer occurs in the essential oil from leaves of Litsea odor ifera. The population viability of tested microbial strains in the presence of the investigated compounds was determined by the impedimetric method. Undecan-2-one showed low activity towards bacteria but it was more efficient in the case of yeasts and moulds. Other tested compounds exhibited different bacteriostatic activity towards B. subtilis and they had no effect on bacteria E. coli and yeast C. mycoderma. The antimicrobial activity of enantiomers was diverse and wasn't always the same as that determined for racemic mixture of the compound. The S(+) enantiomer of undecan-2-ol showed a similar activity to that of the racemic mixture, however both enantiomers of undec-2-yl acetate exhibited higher activity towards bacteria B. subtilis than the racemic mixture. The tested compounds can be used as growth inhibitors of Gram-positive bacteria B. subtilis and mould A. niger in food and cosmetic products.