Yes, MANDRAKE is a Scrabble word!

Letter values in Scrabble US: M 3, A 1, N 1, D 2, R 1, A 1, K 5, E 1.

Is it a valid word?

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

the root of the mandrake plant; used medicinally or as a narcotic
a plant of southern Europe and North Africa having purple flowers, yellow fruits and a forked root formerly thought to have magical powers

Also: mandrake root, devil's apples, mandragora officinarum.