Wiki https://en.wikipedia.org/wiki/Phenolphthalein

Section 1.2, "The discovery of phenolphthalein's laxative effect was due to an attempt by the Hungarian government to label genuine local white wine with the substance in 1900. Phenolphthalein did not change the taste of the wine and would change color when a base is added, making it a good label in principle. However, it was found that ingestion of the substance led to diarrhea."

Oh, the playful innocence of 1900 chemistry!