Bromelain

Bromelain is a proteolytic (protein-digesting) enzyme extracted from the pineapple plant; there is some in the fruit, but the commercial enzyme is mostly derived from the leaves and stems, as they are otherwise wasted and in any case there is more bromelain in them than in the fruit.
Bromelain as a supplement is used for a lot of purposes, and it has commercial uses too. One of the latter uses is its use in meat tenderiser powder; the powder is sprinkled on meat and partially breaks it down, making the meat more tender and palatable.
Bromelain, as a supplement, is chiefly used for two purposes; it is used to help digestion, as it helps digest the protein in food, and it also has anti-inflammatory properties; for this reason, bromelain is used for treatment of minor injuries of joints, tendons and muscles, and also for arthritis, particularly rheumatoid arthritis.
Bromelain is also used for helping with various circulatory problems, particularly if inflammation of the blood vessels is involved; these include phlebitis (vein inflammation) and varicose veins. Bromelain can also be used for various other problems where inflammation is the main part of the problem; ulcerative colitis, Crohn's disease, bronchitis and sinusitis. Bromelain also helps in respiratory problems for another reason; it breaks down the proteins in mucus and therefore makes the mucus more fluid.
Bromelain, taken long-term, also helps reduce the likelihood of various circulatory disorders such as heart disease (including angina) and poor circulation in the brain; it might also help in intermittent claudication. In all these cases, bromelain helps by reducing inflammation (which is thought to be the root cause of most circulatory problems) and therefore helping the body remove the plaque and cholesterol deposits that are the problem in these diseases.
Bromelain can also help in sports injuries, ranging from tendon strains to the sore muscles that result from just a little too much exercise.