Quality Assessment of Bilberry Fruits () and Bilberry-Containing Dietary Supplements.

Bilberries () are used to treat non-specific diarrhea and for symptoms related to varicose veins. Because they are quite expensive fruits, quality problems and compositional fraud might occur for dietary supplements. This study investigated fresh/dried bilberries and dietary supplements by high-performance liquid chromatography (HPLC) fingerprinting against a quantified bilberry reference extract for identity testing and to test total anthocyanin content by HPLC and for quantification of hydrolyzable and condensed tannins. Protocols were detecting improper drying/storage and adulteration with other species or elderberries. The majority (91%) of dried bilberries from different sources proved to be of good overall quality. Investigation of dietary supplements revealed major problems, with 45% of unacceptable quality (e.g., bilberry-free products, nearly anthocyanin/tannin-free products, and samples being falsified with anthocyanins from other sources). Three representative samples of bilberry juices were shown to have good quality in all tested parameters. Increased analytical efforts must be implemented to improve product quality.