Yes, BELLADONNA is a Scrabble word!

Letter values in Scrabble US: B 3, E 1, L 1, L 1, A 1, D 2, O 1, N 1, N 1, A 1.

Is it a valid word?

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

perennial Eurasian herb with reddish bell-shaped flowers and shining black berries; extensively grown in United States; roots and leaves yield atropine
an alkaloidal extract or tincture of the poisonous belladonna plant that is used medicinally

Also: belladonna plant, deadly nightshade, atropa belladonna.