Yes, RETINOL is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, T 1, I 1, N 1, O 1, L 1.

Is it a valid word?

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

an unsaturated alcohol that occurs in marine fish-liver oils and is synthesized biologically from carotene

Also: vitamin a1.