Limonoids are phytochemicals, abundant in citrus

Citrus

Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...

 fruit and other plants of the families Rutaceae

Rutaceae

Rutaceae, commonly known as the rue or citrus family, is a family of flowering plants, usually placed in the order Sapindales.Species of the family generally have flowers that divide into four or five parts, usually with strong scents...

 and Meliaceae

Meliaceae

The Meliaceae, or the Mahogany family, is a flowering plant family of mostly trees and shrubs in the order Sapindales....

. Currently limonoids are under investigation for a wide variety of therapeutic effects such as antiviral

Antiviral

Antiviral may refer to:*Antiviral drug*Antiviral protein*Antivirus software*Antiviral Therapy, an academic journal...

 or Viricide, antifungal, antibacterial, antineoplastic and antimalarial. Certain limonoids are insecticide

Insecticide

An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

s such as azadirachtin

Azadirachtin

Azadirachtin, a chemical compound belonging to the limonoid group, is a secondary metabolite present in neem seeds. It is a highly oxidized tetranortriterpenoid which boasts a plethora of oxygen functionality, comprising an enol ether, acetal, hemiacetal, and tetra-substituted oxirane as well as a...

 from the neem

Neem

Azadirachta indica is a tree in the mahogany family Meliaceae. It is one of two species in the genus Azadirachta, and is native to India growing in tropical and semi-tropical regions. Its fruits and seeds are the source of neem oil...

 tree.

Chemically, the limonoids consist of variations of the furanolactone

Furanolactone

A furanolactone is a heterocyclic chemical compound that contains both a lactone and a furan ring structure.Examples include:* The Salvinorins, including the hallucinogenic compound salvinorin A* Columbin, a potential chemopreventive compound...

 core structure. The prototypical structure consists of 4 six-membered rings and a furan

Furan

Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen. The class of compounds containing such rings are also referred to as furans....

 ring. Limonoids are classed as tetranortriterpenes

Tetranortriterpenoid

The tetranortriterpenoid class of chemical compounds most noted for the chemical azadirachtin, extracted from the neem tree that displays insecticidal properties...

.

Citrus fruits contain the limonoids limonin

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...

, nomilin and nomilinic acid, while both neem seeds and leaves contain the limonoid azadirachtin

Azadirachtin

Azadirachtin, a chemical compound belonging to the limonoid group, is a secondary metabolite present in neem seeds. It is a highly oxidized tetranortriterpenoid which boasts a plethora of oxygen functionality, comprising an enol ether, acetal, hemiacetal, and tetra-substituted oxirane as well as a...

, although higher concentrations are present in the former.