Reviewed August 2026 by the Corydalis Labs Technical Team. How we research and review.
The short definition
The correct name for this compound is 13-OH Corydalis Yanhusuo. It is a hydroxylated alkaloid derived from Corydalis yanhusuo rhizome, related to that plant’s signature isoquinoline alkaloid, tetrahydropalmatine (THP). The name records both the chemistry — a hydroxyl group at the 13 position — and the botanical source, which is the part that actually matters when you are deciding what you are buying. It is a distinct compound from THP: analytically separable, and different in how it behaves inside a formulation.
You will also see it written simply as 13-OH, which is the shorthand used throughout this site and across the trade. Some suppliers write it as "13-OH THP"; we use the botanical name because it is the more precise description of what the material actually is.
If you have arrived here from the kratom category, the single most useful thing to understand is that 13-OH has no relationship to mitragynine. It is not a kratom alkaloid, not a kratom derivative, and not made from kratom. The resemblance to the name "7-OH" is a coincidence of nomenclature — both names simply record where a hydroxyl group sits, in the way that "1-butanol" and "1-propanol" share a naming pattern without being the same substance.
The one-paragraph version
13-OH Corydalis Yanhusuo is a hydroxylated alkaloid sourced from Corydalis yanhusuo rhizome. It is analytically distinct from the plant's parent alkaloid THP, eluting at 18.8 minutes against THP's 15.0 by our HPLC method. Formulators use it at 25–40 mg per serving as a synergist, most often alongside mitragynine, where it lets a target profile be reached at a lower mitragynine inclusion. It is not a kratom alkaloid and, as of August 2026, is not a federally scheduled substance.
Where it comes from
Corydalis yanhusuo is a flowering plant in the poppy family, native to eastern Asia. Its rhizome — the underground stem, harvested and dried — has been used in traditional herbal practice for centuries and is documented in classical Chinese materia medica. That rhizome contains a complex mixture of isoquinoline alkaloids, of which tetrahydropalmatine is the most abundant and most studied.
This lineage matters for reasons beyond marketing. A compound derived from a long-used food-and-herb plant occupies a different position, scientifically and in regulatory terms, than one synthesised to resemble a controlled substance. The plant page covers the botany, the alkaloid profile, and the traditional record in more detail.
Its parent alkaloid: THP
Tetrahydropalmatine is an isoquinoline alkaloid — a structural family entirely separate from the indole alkaloids that mitragynine belongs to. THP has been characterised in the scientific literature for decades and is understood to interact with dopaminergic signalling rather than opioid receptors. It is available as an isolated compound from botanical suppliers and appears in traditional preparations.
13-OH takes that scaffold and adds a hydroxyl group. In alkaloid chemistry, hydroxylation of this kind commonly alters how a molecule is absorbed, how long it persists, and how strongly it engages its targets. In practice, what formulators observe is that the derivative contributes more to a finished blend than an equivalent amount of the parent does. More on THP itself.
How we know it is a distinct compound
The category has a credibility problem: material sold under a name that turns out to be something cheaper. The answer is chromatography. Under our HPLC method, tetrahydropalmatine and 13-OH resolve as two clearly separated peaks — THP at 15.0 minutes, 13-OH at 18.8. A sample that is actually THP cannot masquerade as the derivative under this method, and a lot that contains both shows both.
Every lot we ship carries a certificate of analysis reporting identity and assay, with material typically running 93–98% active. The identity page explains the method, and the quality page covers our testing programme.
What it does in a formulation
The honest headline is that 13-OH is a synergist rather than a soloist. On its own, at the inclusion rates that make commercial sense, it is subtle. Its value shows up in combination, and we would rather say that plainly than oversell a single-ingredient story that your own evaluation would immediately contradict.
What formulators consistently report when 13-OH is added to a mitragynine-forward product:
- Reduced sensory harshness. The most common complaint about mitragynine-forward formats is how they sit with the user physically. Blends including 13-OH are reported as noticeably smoother in this respect.
- A fuller overall character. Products read as rounder and more complete rather than one-dimensional.
- A lower mitragynine requirement. Because 13-OH contributes to the finished profile, the same target can be reached with less mitragynine per serving — which shortens the ingredient statement and lightens the total alkaloid load.
That last point is the one we think matters most, and it is the reason we are in this business. The effects page goes deeper into mechanism and what is and isn't established.
How it is used
Three applications account for nearly everything we supply:
- MIT + 13. Blended into mitragynine tablets and shots at 25–40 mg per serving. Detail here.
- Kratom-free botanical stacks. Combined with kava and kanna for social-relaxation products containing no Mitragyna speciosa material at all — which places them outside state kratom acts entirely. Detail here.
- Standalone with a stimulant. At higher inclusions paired with caffeine or a botanical stimulant, for products with no kratom-derived ingredient. Detail here.
Where it sits legally
As of August 2026, neither 13-OH, nor tetrahydropalmatine, nor Corydalis rhizome extract appears on the federal controlled substance schedules maintained at 21 C.F.R. Part 1308, or on the DEA List I/II chemical lists. Because the salts-and-isomers principle in the Controlled Substances Act extends control to derivatives only where a parent compound is itself scheduled — and tetrahydropalmatine is not — there is no derivative mechanism that reaches 13-OH.
Separately, state kratom acts define their scope around Mitragyna speciosa and its alkaloids. A product containing 13-OH and no kratom material falls outside those definitions.
We have set out the analysis in full, with the primary sources, on the regulatory summary page. It is written so that you can hand it to your own counsel, which is exactly what you should do before commercialising anything. Nothing on this site is legal advice.
Questions we get constantly
No, and the similar names cause real confusion. 7-OH is 7-hydroxymitragynine, an oxidation product of mitragynine from the kratom leaf. 13-OH is a hydroxylated derivative of tetrahydropalmatine from Corydalis yanhusuo, a different plant in a different family, with a different core structure. They share nothing but a naming convention that marks where a hydroxyl group sits on the molecule. The full comparison is here.
No. Kratom is Mitragyna speciosa. 13-OH contains no material from that plant and is not derived from any of its alkaloids. This matters legally as well as chemically, because state kratom acts define their scope around Mitragyna speciosa and its alkaloids. See how state kratom acts treat it.
It is derived from plant material — Corydalis yanhusuo rhizome, a botanical with a long documented history of traditional use. It is a derivative of a naturally occurring alkaloid rather than a compound designed from scratch to mimic something else, which is a meaningful distinction both scientifically and in how regulators have historically approached novel substances.
25 to 40 milligrams per serving is the range that performs in a blend, with 30 mg the most common starting point. Standalone use requires substantially more — generally above 100 mg — and even then it works best paired with caffeine or another botanical stimulant. Full dosing guidance.
As of August 2026, neither 13-OH, its parent alkaloid tetrahydropalmatine, nor Corydalis rhizome extract appears on the United States federal controlled substance schedules or on the DEA List I/II chemical lists. Because the controlled-substances framework extends to salts and isomers only where a parent compound is itself scheduled, and tetrahydropalmatine is not scheduled, there is no derivative mechanism that reaches it. The regulatory summary explains this in detail, and you should review it with your own counsel.
Yes — that is the most common application. In an MIT + 13 blend the mitragynine remains subject to whatever rules apply to it in your markets; adding 13-OH does not change those obligations, and it does not add new ones of its own. How MIT + 13 blends work.
This page is maintained as reference documentation. If you find something here that is wrong, incomplete, or has been overtaken by events, tell us at sales@corydalislabs.com and we will correct it and note the change.