Abstract
Shiikuwasa (Citrus depressa Hayata) is cultivated in the northern areas of the Okinawa main island, Japan. Whole shiikuwasas were extracted for juice processing using extractors. The polymethoxylated flavone nobiletin is a characteristic component of shiikuwasa, and its various biological activities have been extensively reported. In this study, nobiletin concentration in shiikuwasa juice samples was quantitatively determined by high-performance liquid chromatography (HPLC), and the change in nobiletin concentration in shiikuwasa juice during processing was analyzed. Shiikuwasa juice was concentrated with a centrifugal evaporator, and some extraction solvents were examined by HPLC. The optimum extraction solvent was found to be methanol. Nobiletin concentration was determined to be 0.1mg/100g, with a coefficient of variation of 1.8%. A juice sample extracted from only the edible part of the fruit contained a very low nobiletin concentration (0.2mg/100g). Therefore, it was suggested that nobiletin in juice extracted from whole shiikuwasas is from peel tissues. Also, it was indicated that centrifugation during juice processing markedly affects nobiletin concentration in shiikuwasa juice.
