The amounts of limonoate A-ring lactone (LARL) and limonin 17-d-o-glucopyranoside (LG) in navel oranges were measured during fruit growth and maturation. The LARL content (grams/fruit) increased sharply from June to August, reached a maximal level at the end of August, and then decreased gradually thereafter.LG began to appear in the flesh portion in September and in the peel 1 month later. Its content increased sharply from September to November and then slowly thereafter. The decrease in LARL and the increase in LG content occurred simultaneously at late stages of fruit growth and maturation, suggesting that LG is a metabolite of LARL. The amounts of total limonin (LARL + LG) continued to increase until the end of November and then remained fairly constant thereafter. This showed that the biosynthesis of LARL and its further conversion to LG appeared to continue in the fruit until the end of November.Bitterness due to limonin in a variety of citrus juices is major problem of the citrus industry, worldwide, and has significant negative economic impact. In general, bitterness occurs in juices extracted from early-season to midseason fruits of winter citrus, such as navel orange, Shamouti orange, grapefruit, and Natsudaidai. Bitterness is greatly reduced in juice extracted from fruits harvested later in the season. The concentration of limonoate A-ring lactone (LARL), a precursor of limonin, decreases as fruit maturation progresses (Maier et al., 1980). However, how

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Commercial citrus juices were found to contain very high concentrations of limonoid glucosides. TLC analyses showed the presence of these compounds averaging 320,190 and 82 ppm in orange, grapefruit and lemon juices, respectively. The major glucoside in citrus juices was limonin 17-O-8-D-glucopyranoside, which constituted over 50% of the total limonoid glucosides in the juices.

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