Validation of Dried Blood Spot Cards to Determine Apple Phenolic Metabolites in Human Blood and Plasma After an Acute Intake of Red‐Fleshed Apple Snack

Scope The application of dried blood spot (DBS) cards for the study in human blood of dietary polyphenol bioavailability has been poorly studied. Methods and results An analytical method based on blood sampling with DBS cards combined with LC–MS/MS has been developed and validated. To test the method validation, the phenolic metabolites are determined in human blood and plasma obtained after an acute intake of a red‐fleshed apple snack in ten volunteers. Capillary blood by finger prick is compared to venous blood by venipuncture and whole blood is also compared to their corresponding venous plasma samples. Moreover, the venous plasma results using DBS cards are compared to those obtained by microElution solid phase extraction (µSPE). The main phenolic metabolites detected in blood and plasma samples are phloretin glucuronide, dihydroxyphenylpropionic acid sulphate, (methyl) catechol sulphate, catechol glucuronide, and hydroxyphenyl‐γ‐valerolactone glucuronide. No significant differences are observed between capillary blood, venous blood, and plasma samples using DBS, and neither between plasma samples analyzed by DBS or µSPE. Conclusions Finger‐prick blood sampling based on DBS appears to be a suitable alternative to the classic invasive venipuncture for the determination of circulating phenolic metabolites in nutritional postprandial studies. The aim of the present study is to develop and validate an analytical method based on the combination of dried blood spot cards as a self‐sampling blood procedure combined with a sensitive chromatographic method to analyze the main circulating phenolic metabolites after an acute intake of a red‐fleshed apple snack. Results indicate that this method is a suitable alternative to the classic invasive venipuncture for determining phenolic metabolites in nutritional postprandial studies.