Quick supramolecular solvent-based microextraction for quantification of low curcuminoid content in food

Abstract

There is a need to monitor the consumption of curcuminoids, an EU-permitted natural colour in food, to ensure that acceptable daily intakes are not exceeded, especially by young children. This paper describes a sensitive method able to quantify low contents of curcumin (CUR), demethoxycurcumin (DMC) and bis-demethoxycurcumin (BDMC) in foodstuffs. The method was based on a single-step extraction by use of a supramolecular solvent (SUPRAS) made up of reverse aggregates of decanoic acid, and direct analysis of the extract by use of liquid chromatography-photodiode array (PDA) detection. The extraction involved the stirring of 200 mg foodstuff with 600 μL SUPRAS for 15 min. No cleanup or concentration of the extracts was required. Curcuminoid solubilisation occurred via dispersion and hydrogen bonding. The method was used for the determination of curcuminoids in different types of foodstuff (snack, gelatine, yoghurt, mayonnaise, butter, candy and fish products) that encompassed a wide range of protein, fat, carbohydrate, sugar and water contents (0.85-11.04, 0-81.11, 0.06-75, 0.06-79.48, and 10.08-85.10 g, respectively, in each 100 g of food). Method quantification limits for the foodstuffs analysed were in the ranges 2.9-7.7, 2.8-11.2 and 3.3-9.0 μg kg(-1) for CUR, DMC and BDMC, respectively. The concentrations of curcuminoids detected in the foodstuffs and the recoveries obtained from fortified samples were in the ranges ND-284, ND-201 and ND-61.3 μg kg(-1), and 82-106, 89-106 and 90-102 %, for CUR, DMC and BDMC, respectively. The relative standard deviations were in the range 2-7 %. This method enabled quick and simple microextraction of curcuminoids with minimal solvent consumption, while delivering accurate and precise data.