IC50, EC50 and LC50 - (Jun/30/2012 )

Hi,

can someone explain what exactly are IC50, EC50 and LC50 ? or suggest good reference book on concept of IC50, EC50 and LC50. Which one is the most suitable to measure the cytotoxicity of plant extract on the cancer cell line ?

thank you.

Here you go:

EC50 http://en.wikipedia.org/wiki/EC50
IC50 http://en.wikipedia.org/wiki/IC50
LC50 http://en.wikipedia.org/wiki/LC50