Biosynthesis of synephrine in citrus

Synephrine is formed in citrus by a pathway involving tyramine and N-methyltyramine. Octopamine is probably not an important intermediate. 14C-labeled tyramine was converted to N-methyltyramine, hordenine, octopamine, and synephrine in one of the citrus cultivars studied. Tyrosine was a less efficient precursor and phenylalanine, serine, ethanolamine, and epinephrine were ineffective.