The isoflavonoids are all colourless. Since chalcones and flavanones are efficient precursors of isoflavonoids, the required aryl migration of ring B from the former 2 or beta position to the 3 or alpha position of the phenylpropanoid precursor must take place after formation of the basic C 15 skeleton. It is an insecticide and also used as a fish poison. Biochemical pathway to the formation of rotenone. Six rotenoid esters occur naturally and are isolated from the plant Derris eliptica found in Southeast Asia or from the plant Lonchocarpus utilis or L. urucu native to South America.
Rotenone is the most potent.
It is unstable in light and heat and almost all toxicity can be lost after two to three days during the summer. It is very toxic to fish, one of its main uses by native people over the centuries being to paralyze fish for capture and consumption. Because the toxicity of derris powders exceeds that of the equivalent content of rotenone, it is obvious that the other esters in crude preparations have significant biologic activity. The estimated fatal oral dose for a 70kg man is of the order of 10 to 100g. The Biochemical Mode of Action of Pesticides.