Limonoid

Limonoids are phytochemicals, abundant in citrus fruit and other plants of the classes Rutaceae and Meliaceae. They account for the scent of fresh lemon or orange peel. Many of the plants used in traditional healing, such as Neem, are rich in limonoids. Currently limonoids are under investigation for a wide variety of therapeutic effects such as antiviral, antifungal, antibacterial, antineoplastic and antimalarial. They also show effectiveness as insecticides both in traditional farming cultures and modern biochemistry labs.

Chemically, the limonoids consist of variations of the furanolactone core structure. The prototypical structure consists of 4 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.