The main ingredient in aspirin is salicylic acid, says CNN. Salicylic acid is found in shrubs and plants, such as jasmine, peas, beans and clover along with some grasses and trees.
The form of salicylic acid used in modern aspirin is acetylsalicylic acid, which was first used by chemist Felix Hoffman in Germany in the late 1890s. Aspirin became commonly used as an over-the-counter medication in 1915. In 1948, based on his observations in his medical practice, Dr. Lawrence Craven recommended an aspirin a day for heart health. More than 33 percent of adults and 80 percent of people with heart disease use aspirin daily.