Like Jamncristian, I don't think its suitable. Panthers don't usually graze much, but it seems like other plants would be safer and better choices.
I have no references that indicate that _Homalomena_ is toxic, except in Mabberly, " some ... locally used poisons". It is in the Aroid family and like most of them, it is likely to have rhaphides of calcium oxalates. These cause immediate sensations of burning in the mouth when eaten. Most Aroids are not eaten for this reason, but there is some risk of harm.