7-Hydroxymitragynine

7-Hydroxymitragynine (7-OH) is a terpenoid indole alkaloid from the plant Mitragyna speciosa, commonly known as kratom. It was first described in 1994 and is a natural product derived from the mitragynine present in the kratom leaf. 7-OH binds to opioid receptors like mitragynine, but research suggests that 7-OH binds with greater efficacy.

Pharmacology
7-Hydroxymitragynine, like mitragynine, appears to be a mixed opioid receptor agonist/antagonist, acting as a partial agonist at μ-opioid receptors and as a competitive antagonist at δ- and κ-opioid receptors. Evidence suggests that 7-OH is more potent than both mitragynine and morphine. 7-OH does not activate the β-arrestin pathway like traditional opioids, meaning symptoms such as respiratory depression, constipation and sedation are much less pronounced.

7-OH is generated from mitragynine in vivo by hepatic metabolism and may account for a significant portion of the effects traditionally associated with mitragynine. Although 7-OH occurs naturally in kratom leaves, it does so in such low amounts that any ingested 7-OH is inconsequential compared to the 7-OH generated in the body.

Metabolism
7-Hydroxymitragynine can convert into mitragynine up to 45% in human liver microsomes over a 2 hour incubation and was degraded up to 27% in simulated gastric fluid and degraded up to 6% in simulated intestinal fluid. 7-Hydroxymitragynine can metabolize to mitragynine pseudoindoxyl in the blood but not in the liver. Interestingly, this even more potent opioid was revealed to exist in a mixture of stereoisomers in biological systems.