Limonin

Limonin is a limonoid, and a bitter, white, crystalline substance found in citrus and other plants. It is also known as limonoate D-ring-lactone and limonoic acid di-delta-lactone. Chemically, it is a member of the class of compounds known as furanolactones.

Presence in citrus products
Limonin and other limonoid compounds contribute to the bitter taste of some citrus food products. Researchers have proposed removal of limonoids from orange juice and other products (known as "debittering") through the use of polymeric films.

Research
Limonin is under basic research to assess its possible biological properties.