The amounts of limonoate A-ring lactone (LARL) and 17-β-D-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 increas in LG content occurred simultaneously at late stages of fruit growth and maturation, suggesting that LG is a metabolite of LARL. (...)