Identification of urinary biomarkers after consumption of sea buckthorn and strawberry, by untargeted LC–MS metabolomics: a meal study in adult men

Abstract

Berries may improve health; however, accurate assessment of berry intake is still problematic. The discovery of objective biomarkers for intake of berries is therefore important in assessing both intake and compliance. We aimed to identify urinary exposure markers of two very different berries, strawberry and sea buckthorn, in humans. A randomized controlled single-blinded three-way cross-over meal study was conducted in 16 overweight men. The intervention meals consisted of sea buckthorn puree, strawberry puree or an iso-caloric control drink. Urine samples were collected on each test day at t = −15 min, t = 0–1 h, t = 1–2 h, and t = 2–24 h and were analyzed by untargeted metabolomics. Multivariate analysis was applied to discover markers, followed by molecular fragmentation to ease their chemical identification. Only a few common markers appeared for the two berries, and all except one were in very low concentrations and therefore not identified. Nine and 11 markers were (tentatively) identified for strawberry and sea buckthorn, respectively, the most specific being conjugates of aroma compounds and coloring flavonoids. Metabolites reflecting the step-wise aromatization of quinic to hippuric acid were observed after sea buckthorn intake. Three of the identified compounds validate previously proposed exposure biomarkers for the New Nordic Diet, which is high in berries. Potentially common berry exposure markers, as well as an aromatization pathway have been distinguished by human urine profiling after consumption of sea buckthorn or strawberries. Combinations of these markers are proposed as potentially specific for intake of each of these berries, but need further validation in larger and less-controlled study settings.