Papaya (also known as paw paw) is a small tree native to the tropical regions of the Americas, now found in tropical areas throughout the world. The tree's hollow trunk produces large, deep-lobed leaves and smooth-skinned, melon-like fruits, which are born directly on the trunk's surface, without intervening branches. When shallow cuts are made in the fully grown, unripe fruit, they produce a milky latex known as papain, which contains a mixture of protein-digesting enzymes. When ripe, the fruit is a popular food.
The primary active constituents in papaya are a group of proteolytic (protein-digesting) enzymes which includes papain, chymopapain, and papaya proteinase III. Papaya also contains vitamin C, malic acid, and citric acid.
Papaya is consumed widely as a food with no evidence of toxicity. Papaya tablets containing 10 to 50 mg of papain are commonly used as digestive aids and appear to be safe, although their effectiveness for this purpose has not been proven.