What is Rotenone?

Rotenone is a naturally occurring rotenoid plant extract from South America, Australia and many countries in Southern Asia.  It is found in the roots and stems of several tropical plants, Jewel vine (Derris spp.), Lacepod (Lonchocarpus spp.) and Hoary Pea (Tephrosia spp.) being the most common.

This picture was obtained from http://www.awlonline.com/mathews/ch15/rotenone.htm
Rotenone has an empirical formula of C23H22O6 and has a molecular weight of 394.41.  Its melting point is 165-166C.  Rotenone is very soluble in many organic solvents, for example alcohol and acetone, but is almost completely insoluble in water.

Rotenone is generally unstable and will decompose quickly in water, sometimes as fast as two weeks after its application.  However, it can sometimes persist for up to six months depending on a variety of factors including light, temperature, depth, dose and presence of organic debris.  Rotenone readily breaks down in the presence of light into at least 20 products, only one of which, 6ab, 12ab-rotenolone, is toxic.  None of the other This picture was obtained from http://www.hear.org/pier3/deellp.htm
degradation products are toxic meaning it is considered safe for use on land and in water.  The decomposition process occurs at a faster rate as the temperature of the water increases.  The depth and the presence of organic debris in the water will affect the amount of light and therefore the rate of rotenone degradation, as a lack of light corresponds to a slower rate of degradation.

For centuries, South and Central American people have used the Jewel vine to stun fish.  When the vine is crushed up and thrown into the water, the fish cannot inhale oxygen through their gills and come to the surface, making it possible for them to kill the fish with their bows and arrows.  Also, in World War Two, Rotenone was used to kill lice in the trenches.  These are the two main commercial uses of Rotenone today, as a piscicide and as an insecticide.