From the Super Mario Wiki
A Slimy Extract is a recipe in the game Super Paper Mario made by Saffron. It is a mysterious Shroom extract that cures curses and Poison. It is made from a Slimy Shroom.
It's only useful in Chapter 5: between Chapter 1 and 4, the slimy shroom can only be obtained with 150 shop points, and it isn't very convenient. After chapter 4, it can be obtained with only 40 coins in Flopside inn, but after Chapter 5 Piccolo can be obtained, making the extract useless.
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