Twenty five years of azadirachtins (1986-2011)

Azadirachtins are known as phagorepellent natural products from seeds of the neem tree Azadirachta indica A. Juss (Meliaceae), which impede the development of larval insects and sterilize adults. The labors of the past three decades ultimatively lead to a chemical structure, which has been unanimously but independently elaborated by German, British and American authors. This structure is in force ever since 1985/87 and was ultimately confirmed by Veitch & al. in Ley’s group in Cambridge, England, through total synthesis. Its 25th birthday is presently being celebrated. Marrangin (=Azadirachtin L) was discovered in Gießen and chemically identified by Kalinowski and colleagues. It occurs in seeds of the marrango tree, Azadirachta excelsa (Jack) Jacobs. In some insect species but also in mites like Tetranychus urticae, its biological activity is significantly superior to azadirachtin A. The value of these biorational compounds, with their very low vertebrate toxicity, and their low toxicity today is globally recognized. Quite recently, azadirachtin and analogues gain acceptance in veterinary and human medicine