Aloe vera
Of the 500+ species, only a few were used traditionally as herbal medicines, "Aloe vera" again being the most commonly used species. Also included are "A. perryi" and "A. ferox". The Ancient Greeks and Romans used "Aloe vera" to treat wounds. In the Middle Ages, the yellowish liquid found inside the leaves was favored as a purgative. Unprocessed aloe that contains aloin is generally used as a laxative, whereas processed juice does not usually contain significant aloin.