1) Opioid peptide 
The rubiscolins are a group of opioid peptides that are formed during digestion of the ribulose bisphosphate carboxylase/oxygenase (Rubisco) protein from spinach leaves. Rubiscolins mimic the effects of opiates and, therefore, influence the brain. These peptides have much in common with the better-known gluten exorphins. There are 2 known rubiscol...