Quantitation of Nine Scopoletin Analogues Using an HPLC-Fluorescence Method and Its Application to Morinda Citrifolia (Noni) Products

抄録

Scopoletin (Sco) and its analogues (Scos) are included in various functional food materials. Quantitation of Scos in foods is useful for quality evaluation purposes. In this study, an HPLC-fluorescence method was developed for analyzing Scos emitting native fluorescence in functional food materials. Sco, esculetin (Est), umbelliferone (Umb), isoscopoletin, isofraxidin, esculin, fraxetin, fraxin, and nodakenin could be separated within a retention time of 25 min by gradient elution of a Wakopak Handy ODS column (100 × 4.6 mm i.d., 6 μm) using 15 mmol/L phosphate buffer (pH 2.5) and acetonitrile. The limits of detection for Scos at a signal-to-noise ratio of 3 ranged from 7.10×10−3 to 1.39 ng/mL. Additionally, sufficient validation parameters for quantitating Scos in Noni products were obtained, with an accuracy of 67.9-117.3 %, intra-day precision of <11.7 %, inter-day precision of 9.0 %, and recovery of 67.7-114.0 %. Moreover, the proposed method was applicable to the quantitation of Scos in four Noni products. Sco, Esn, and Umb were in the ranges 9.17-34.5 μg/mL, 39.3-210.3 ng/mL, and 54.5-227.3 ng/mL, respectively, in all samples examined. The method is thus considered useful for quantifying levels of Scos in functional food materials.