The use of plants to tenderize meats dates back to the native peoples of what now is Mexico; they wrapped meat in papaya leaves. Papaya contain enzymes that break down the collagen - the connective tissue that makes meat tough. Pineapple has similar properties. These enzymes, papain (from papaya) and bromelain (from pineapple) are the active ingredients in bottles of meat tenderizers. If you want to try these be aware they only effectively tenderize the outer layers of a thick tough cut of meat. But if you cut your meat thin and apply the tenderizer to both sides it will probably do the job. Neither brand nor type of enzyme seems to make any difference. They do come with seasoning but down here in Louisiana we like to do our own seasoning so  just purchase the unseasoned bottles.