Determination of Organosulfides from Onion Oil

Abstract

Qualitative and semiâquantitative analysis of organosulfides extracted from oil obtained by steam distillation of yellow onions was performed by gas chromatographyâmass spectrometry (GCâMS). The extraction efficiency of organosulfides from onion oil was evaluated across four solvents: Dichloromethane; diethyl ether; nâpentane; and hexanes. Analysis of solvent extracted organosulfides by GCâMS provided qualitative results that support the use of dichloromethane over other solvents based on identification of 27 organosulfides from the dichloromethane extract as compared to 10 from diethyl ether; 19 from nâpentane; and 17 from hexanes. Semiâquantitative evaluation of organosulfides present in the dichloromethane extract was performed using diallyl disulfide as the internal reference standard. Three organosulfides were detected in the extract at ≥5 mg/kg; 18 organosulfides between 3-5 mg/kg; and six organosulfides at <3 mg/kg. The E/Z isomers of 1âpropenyl propyl trisulfide were among the most prevalent components extracted from the onion oil across all solvents; and 3,6âdiethylâ1,2,4,5âtetrathiane was among the most abundant organosulfides in all solvents except hexanes. The method described here for the extraction of organosulfides from steam distilled onion oil surveys common solvents to arrive at a qualitative and semiâquantitative method of analysis for agricultural products involving onions; onion oil; and secondary metabolites of Allium spp.Â