Comprehensive Review Maps Pharmacology and Toxicology of Kratom's Key Alkaloids

Why it matters

A systematic review synthesizing 150 studies on mitragynine and 7-hydroxymitragynine — kratom's two primary active alkaloids — offers the most thorough existing analysis of their chemistry, biological effects, and research gaps, giving clinicians and policymakers a critical knowledge baseline.

The big picture

Despite growing public and regulatory interest in kratom, scientific literature on its key alkaloids has been scattered and incomplete. This open-access review fills that gap by aggregating findings on mitragynine and 7-HMG from PubMed, ScienceDirect, and Google Scholar, revealing where knowledge is solid and where major research gaps remain.

Key findings

• Most scientific studies focus on kratom leaves, leaving flowers and other plant parts almost entirely unstudied
• Mitragynine has been more intensively studied than 7-hydroxymitragynine, though both bind to opioid receptors
• Existing extraction and synthesis protocols for the two alkaloids are costly and time-consuming, limiting research scalability
• Some lesser-studied alkaloids in kratom may exhibit stronger pharmacological activity than mitragynine or 7-HMG
• The review identifies critical gaps in long-term human toxicity data and clinical pharmacokinetics

What they say

The authors noted: "Most studies have focused on these two alkaloids to explore their pharmacological effects, although some studies have shown that other alkaloids exhibit better pharmacological activity" — pointing toward an underexplored frontier in kratom research.

Bottom line

A sweeping 150-study review reveals that while kratom's main alkaloids are increasingly understood, major gaps in human toxicity and long-term clinical data leave key safety and efficacy questions unanswered.