It's wild to me that that molecule and it's derivatives are so localized to certain species. For folks information, Tyrian purple is indigo that has been substituted on both ends with bromine groups (6,6'-dibromoindigo). Indigo itself is only found in a couple species (indigo and woad are the most prevalent). Also Tyrian purple was harvested by "milking" a certain snail for minute amounts of the dye.

I went to a farm near me to buy some madder (the roots of which contains the anthraquinoidal dye alizarin) and one of the farmers, an older man, told me all of that above and I asked him if he was a chemist? Non chemists don't use words like "substituents."

"In a past life," he said.