(R)-salsolinol + S-adenosyl-L-methionine <=> N-methyl-(R)-salsolinol + S-adenosyl-L-homocysteine + H(+)
(r)-salsolinol + s-adenosyl-l-methionine <=> n-methyl-(r)-salsolinol + s-adenosyl-l-homocysteine + h(+)