Introduction Many insecticidal compounds are known from plants. Most plants make defensive compounds called allomones. Few are important commercially. Plant-derived insecticides have largely been replaced by synthetic materials, but there are some advantages to the naturally occurring materials. For example, these substances are biodegradable.
Selectivity is needed.
Compounds that are toxic to insects, but not toxic to mammals, are preferable, of course. Commercially, rotenoids are isolated mostly from the roots of Derris elliptica in Indonesia and from Lonchocarpus in South and Central America. These compounds are isolated by grinding the plant and extracting with solvents such as hexane or petroleum ether or chloroform. The compounds are oil soluble or lipids. These were used as far back as the 1st century B.C. by the Chinese.