Identification of unknown compound extracted from the hair of exhumed human remains using mass spectrometric and gas chromatographic data

Abstract

The real example of GC-MS identification of unknown constituent of human hair extract belonging to the exhumed remains is considered. The identification of this constituent (molecular weight 238 Da) was unsuccessful using both its standard mass spectrum (electron ionization) in combination with lib­ra­ry search, and its GC retention index value (~1540 on semi-standard non-polar polydimethyl siloxane stationary phases with 5% phenyl groups). However, its identification appea­red to be possible using the original algorithm of data processing. This approach implies revealing the structural analogues of unknown analytes, primarily their homologues which differ by molecular masses on ± 14 Da and by composition on CH2 homolo­go­us difference. This approach allowed revealing such analogues of unknown analyte as Flavesone (2,2,4,4-tetramethyl-2-isobutyrylcyclohexa-1,3,5-trione), Leptospermone (2,2,4,4-tetramethyl-2-isopentanoylcyclohexa-1,3,5-trione), and some others. All these compounds belong to a rather “exotic” class of natural compounds knows as cyclic b-triketones. Based on the obtained data, the possible structure of the constitu­ent under the consideration was proposed as 2,2,4,4-tetramethyl-2-propionylcyclohexa-1,3,5-trione. The principal fea­ture of cyclic b-triketones is their existence in a few tautomeric forms. Another tautomer of triketone under discussion is 5-hydroxy-2,2,6,6-tetramethyl-4-propionyl-4-en-1,3-dio­ne (CAS № 87552-01-0). This compound is found to be the constituent of Leptosper­mum scoparium essential oil and some other plants, and it belongs to the group of structural analogues of Flave­sone. The most known pharmaceutical application of essential oils containing these compounds are the components of conditioners for hair and skin. The results confirm this formerly un­known component does not belong to the group of toxic substances. This excludes the criminal origin of the remains.