Dihydrosanguinarine is a
benzylisoquinoline alkaloid produced in plants from the amino acid
tyrosine. A sequence of enzyme-catalysed reactions gives
(S)-norcoclaurine which goes through three further transformations to yield (
S)-3'-hydroxy-N-methylcoclaurine. (
S)-reticuline is made when the enzyme
3'-hydroxy-N-methyl-(S)-coclaurine 4'-O-methyltransferase adds a
methyl group. Reticuline is a branch point in the biosynthesis: the (
R)
enantiomer is used to eventually produce
morphine, for example in the opium poppy
Papaver somniferum while other pathways use the initially-formed (
S) isomer leading to sanguinarine via dihydrosanguinarine. The immediate precursor to dihydrosanguinarine is protopine, which is oxidised by
protopine 6-monooxygenase to 6-hydroxyprotopine, a compound which spontaneously forms the final ring system. The last step in the sequence to sanguinarine is catalysed by the enzyme
dihydrobenzophenanthridine oxidase: == See also ==