Changes in the limonoate A-ring lactone and limonin 17-.beta.-D-glucopyranoside content of navel oranges during fruit growth and maturation

Abstract

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

The Chemistry and Pharmacology of Citrus Limonoids

“…Lastly, a method has been reported for the identification of limonoid A ring lactones in citrus samples. In fact, since only indirect chemical and biochemical techniques [157][158][159] or MS detection were available, Breksa III et al finally developed a rapid and reliable LC-ESI-MS method for the direct quantification of limonoate A Rring lactone (LARL, 47, Figure 15) and nomilinoate A ring lactone (NARL, 48, Figure 15) in a wide variety of citrus juices. These limonoid A-ring lactones were isolated by solid-phase extraction from juice samples and analyzed by negative ion LC-ESI-MS while their concentrations were established by fluorescence spectroscopy [160].…”

Purification of limonoid glucosyltransferase from navel orange albedo tissues

“…In navel orange grown in California, the natural glucosidation of limonoid aglycones begins in September and continues until the fruit is harvested [4]. The harvesting season of navel oranges begins in November.…”

“…The limonoid glucosides are practically tasteless. The glucosylation of limonoid aglycones is catalysed by UDP-D-glucose:limonoid glucosyltransferase (limonoid GTase) [4]. The objective of this research was to purify the GTase from citrus fruits and characterize it.…”

Limonoid Glucosides in Juices of Satsuma Mandarin(Citrus unshiuMarc.)

“…The conversion of limonoid aglycones to their glucosides occurs in fruit tissues during late stage of fruit growth and maturation. 9) This conversion has been demonstrated in navel oranges. The high concentration of limonoid glucosides and low concentration of limonoid aglycones (less than 3 ppm) clearly show that this conversion is also occurring in Satsuma mandarin.…”