Melatonin levels in mothers in the 1st, 2nd, and 3rd Trimester Voiculescu etal, 2014 Melatonin levels during development Grivas and Savvidou, 2007 The final step in production of Melatonin is the methylation of N-Acetyl-Serotonin (NAcSer) by the enzyme HydroxyIndole-O-methyltransferase (HIOMT), which has an absolute requirement for S-Adenosylmethionine (SAM), a product of the methylation cycle (Axelrod and Weissbach 1960, Weissbach and Axelrod 1960)
Waheed SM, Ghosh A, Chakravarti R, Biswas A, Haque MM, Panda K, et al
They have no incentive to fast-track things that work
For injection use, look for 99% purity with a Certificate of Analysis (COA) from an independent lab
"Peptide therapy with pentadecapeptide BPC 157 in traumatic nerve injury." Regulatory Peptides