Development and experimental application of an HPLC procedure for the determination of capsaicin and dihydrocapsaicin in serum samples from human subjects.

ABSTRACT

Total capsaicins are extracted from 2 mL aliquots of serum or plasma using methyl-isobutyl ketone, evaporation of the extract to dryness and reconstitution with 200 µL of acetonitrile. The HPLC mobile phase is 4060 wateracetonitrile. The absorbance of the eluent is monitored at 205 nm. Standardisation uses a known mixture of pure capsaicin and dihydrocapsaicin. Accuracies are 98.9 and 100.6 % for capsaicin and dihydrocapsaicin respectively. Inter batch reproducibility for both is 15 %. The limits of detection are 2.6 and 3.8 ng/mL for capsaicin and dihydrocapsaicin respectively. Analyses of sera obtained previously from human subjects who had eaten chilli containing meals showed that in those that absorbed capsaicins (N = 30) then the median, mean and SD of their serum capsaicin were 13.4, 18.9 and 16.3 ng/mL. The corresponding data for those sera (N = 13) that had measurable levels of dihydrocapsaicin were 6.9, 7.5 and 3.6 ng/mL. This procedure is suitable for use in prospective studies of the metabolism of orally ingested chilli.