Yes, PTOMAINE is a Scrabble word!

Letter values in Scrabble US: P 3, T 1, O 1, M 3, A 1, I 1, N 1, E 1.

Is it a valid word?

PTOMAINE is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

any of various amines (such as putrescine or cadaverine) formed by the action of putrefactive bacteria
a term for food poisoning that is no longer in scientific use; food poisoning was once thought to be caused by ingesting ptomaines

Also: ptomaine poisoning.