Limonoids are phytochemicals, abundant in citrus fruit and other plants of the families Rutaceae and Meliaceae. Currently limonoids are under investigation for a wide variety of therapeutic effects such as antiviral or Viricide, antifungal, antibacterial, antineoplastic and antimalarial. 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 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.