Back in Drum he used a mushroom called Amiudake that he called a panacea. That's probably what he gave Zoro.
The
Amiudake (アミウダケ
Amiudake?) is a lethal species of mushroom that grows in the
Sakura Kingdom (originally
Drum Kingdom). Anyone who ingests the fungus will die an hour after consumption. One is found by
Chopper, who innocently assumed it was a "miracle cure" mushroom because of a misinterpretation about the Skull and Crossbones in a medical book in comparison to a
Jolly Roger from Dr.
Hiriluk, to cure his fatal disease. Dr. Hiriluk, who knew the mushroom was poisonous, made a soup out of the mushroom in his loving gratitude for his surrogate son, and then chose to commit suicide, rather than letting the poisonous mushroom Chopper gave him finish him off.
yeah I don't know about that