What is "limonoid"

n. Any of a class of phytochemicals, found in citrus fruit and certain other plants, believed to have various therapeutic effects.

Limonoids are phytochemicals, abundant in citrus fruit and other plants of the families Rutaceae and Meliaceae. Currently, limonoids are under investigation for possible effects in humans, although no proof of effect exists to date. Certain limonoids are insecticides such as azadirachtin from the neem tree.

Chemically, the limonoids consist of variations of the furanolactone core structure. The prototypical structure consists of four six-membered rings and a furan ring. Limonoids are classed as tetranortriterpenes.

Citrus fruits contain the limonoids limonin, nomilin and nomilinic acid, while both neem seeds and leaves contain the limonoid azadirachtin, although higher concentrations are present in the former.