Simultaneous determination of dietary isoprenoids (carotenoids, chlorophylls and tocopherols) in human faeces by Rapid Resolution Liquid Chromatography

Abstract

An analytical method was validated for the quantitative determination of isoprenoids compounds in faecal samples, based on liquid-liquid extraction from a small aliquot (0.3-0.5 g of sample) and subsequent analysis by Rapid Resolution Liquid Chromatography (RRLC) on a C30 column. An excellent linear response was observed over the range specified for all dietary isoprenoids, as confirmed by the correlation coefficient, which ranged from 0.9977 to 0.9999. LODs ranged from 0.002 μg to 0.036 μg for lutein and α-tocopherol, respectively. Depending on the compound, LOQs ranged from 0.001 μg (lutein) to 0.120 μg (α-tocopherol). For accuracy testing, spiking of faeces samples with trans-β-apo-8′-carotenal, α-tocopherol and chlorophyll a were performed (three concentration levels). Excellent recoveries were obtained in all levels (>90%). The intra-day RSD% ranged from 0.86 to 9.78%. The inter-day RSD% was not higher than 10%, except to α-tocopherol (11.34%).

In order to assess the applicability of the method faecal samples from a baby fed with different purees formulated from various vegetables were analysed during a six month period. α-carotene, β-carotene, capsanthin, lycopene, lutein, phytoene, phytofluene, violaxanthin, zeaxanthin and ζ-carotene), and their isomers were identified and quantified using this method. Besides, 2 tocopherols and 9 chlorophylls and derivatives were identified and quantified in the faecal samples analysed. This method is suitable to determine dietary isoprenoids from complex matrices such as human faeces within 28 min.