Limonoic acid A-ring lactone, a new limonin derivative in Citrus

A nonbitter derivative of limonin (the intensely bitter tetracyclic dilactone of Citrus seeds) has been found to occur in the fruit tissues of Citrus sinensis (L.) Osbeck and C. paradisi Macf. The new compound, for which the name limonoic acid A-ring lactone is proposed, is one of the two possible monolactones which can be derived from limonin by partial hydrolysis. It was identified as the A-ring monolactone by TLC and paper electrophoretic comparison with the authentic compound and by its facile conversion into limonin. Indications were found of an enzyme in tissue extracts which converts limonoic acid A-ring lactone into limonin.