Determination of anthocyanins from black carrots by UHPLC-PDA after ultrasound-assisted extraction

Anthocyanins from black carrots (Daucus carota ssp. sativus var. atrorubens Alef.) are widely applied to impart bright red hues to foods such as beverages, fruit preparations, and confectionary. Highly efficient methods for their analyses may be instrumental for manufacturers of coloring foodstuff and for plant breeders to select highly pigmented black carrot varieties. For this purpose, a rapid and exhaustive ultrasound-assisted extraction procedure for anthocyanins was developed and validated. Thereby, deteriorative enzymes like polyphenol oxidase and peroxidase were inactivated. Extraction required only 60 s, yielding coefficients of variation (CVs) for intra-day and inter-day repeatability of ≤4.4 and 4.7%, respectively. For post-extractive quantitation of black carrot anthocyanins, a rapid UHPLC-PDA method was developed and validated. Compared to HPLC separation on a core-shell-column, UHPLC separation time (4.5 min) was 8.2 times faster and solvent consumption 92% less. Limits of detection and quantitation were fully satisfactory. Moreover, stability of non-acylated pigments used as reference compounds was acceptable for 24 h at room temperature, and within 4.5 months of storage time at −20 °C and −80 °C, pigment concentration remained unchanged. Two black carrot varieties were analyzed applying the proposed method, and the results were compared to previously published data.