Contents and antioxidant capacity of limonin and nomilin in different tissues of citrus fruit of four cultivars during fruit growth and maturation

The contents of limonin and nomilin in different fruit tissues of Foxiangyou (Citrus grandis), Citrus unshiu, Penggan (Citrus reticulata) and Huyou (Citrus changshanensis KS Chen et CX Fu) were measured during fruit growth and maturation by HPLC (high performance liquid chromatography). Results showed that limonin and nomilin were the predominant limonoids in the extracted samples. During fruit growth and maturation, the contents of limonin and nomilin increased from April, peaked in early September and decreased afterwards until late October when they reached a steady low level. The antioxidant capacities of limonin and nomilin in the four tissues of mature fruit were determined by β-carotene bleaching assay. The results showed that the antioxidant capacities of limonin and nomilin varied in different tissues and cultivars. In the three tissues other than albedo, the antioxidant capacities of limonin and nomilin were high (2.9-8.3 times than that of vitamine C).