The base is plain lye soap. However, as with most things, there's been some progress and evolution in the recipe. The original bait used blood as the main attractant. Now, fishermen are creating their own recipes that incorporate chemical attractants in liquid. solid, and gel forms. I've even found recipes that use ground up chicken livers, fish oils, and preservatives to keep fresh ingredients from spoiling.
I figure baits, such as these, will eventually lead to catfish being wiped out or catfish will evolve to be smarter than the fishermen and their baits.