If you’re looking at a tablet, capsule, or shot labeled “Cat’s Claw” or “Rhynchophylline” at a smoke shop or gas station, here’s the short version: the herb on the label is harmless, but these products aren’t the herb. They’re built around opioid-active compounds, and the cat’s-claw name is there to keep them off the radar as 7-OH and its relatives get scheduled. If one of these hits you like an opioid, that’s because it is one.
What’s actually in these products
Testing on the newer “Cat’s Claw” product lines has reported some mix of:
- Corynoxine B, an opioid-active alkaloid covered in detail below
- MGM-15, a semi-synthetic opioid derived from 7-OH
- undisclosed synthetic compounds with no published pharmacology at all
What any given product contains varies by brand and by batch. The label won’t tell you, and neither will a standard drug test.
Corynoxine B, the alkaloid doing the work
Corynoxine B is a minor oxindole alkaloid that occurs naturally in kratom itself and across the Uncaria (cat’s-claw) genus. It isn’t synthetic, and it isn’t new to science. What’s new is its use as a product’s active ingredient.
At the receptor it behaves like an opioid. The 2026 study that characterized the kratom alkaloids found corynoxine B binds the mu-opioid receptor with moderate affinity (Ki ≈ 118 nM, in the same range as 7-OH) and drives G-protein signaling as a high-efficacy partial agonist (EC₅₀ ≈ 193 nM, Emax ≈ 81%), with negligible activity at the kappa and delta receptors. Mu is the receptor most responsible for opioid effects and opioid dependence, so a product built around corynoxine B produces opioid effects and opioid dependence.
There’s no human safety, dosing, or long-term data on isolated corynoxine B. A product built around it carries the same dependence, tolerance, and withdrawal as any other mu agonist, with none of the labeling or dose control that even a prescription opioid comes with.
”Cat’s claw” is the cover story
Corynoxine B is what makes the cover story hold together, because three things are true of it at once:
- It’s a genuine cat’s-claw and kratom alkaloid. Both plants are in the Rubiaceae family (so is coffee); they’re botanical cousins that share several alkaloids. So “it’s a cat’s-claw alkaloid” isn’t a flat lie the way “it’s just kratom” was.
- It’s opioid-active, so the product actually does something to the customer.
- It isn’t scheduled. The July 2026 DEA notices name 7-OH above a threshold, mitragynine pseudoindoxyl, MGM-15, and MGM-16. Corynoxine B is a different molecule and appears in none of them. Because the 7-OH rule is written around 7-hydroxymitragynine content specifically, a corynoxine-B product can sit under that threshold and still deliver opioid effects.
The alkaloids marketers usually point to when they invoke the cat’s-claw name, mitraphylline and rhynchophylline, are the harmless ones. The same 2026 study found neither shows measurable binding at opioid receptors. Real Uncaria tomentosa is a traditional anti-inflammatory and immune-support herb; on its own it produces no euphoria, sedation, or opioid pain relief. The marketing leans on the benign alkaloids and the real herb’s reputation while the product runs on something else. It’s the same move tianeptine made with “Tianaa” and “Zaza”: a name nobody’s watching, a potent agonist inside.
The synthesis angle makes this worse
Corynoxine B is the current ingredient, but the cat’s-claw scaffold is also a starting point for compounds that don’t exist in any plant. Researchers have used precursor-directed biosynthesis with Uncaria guianensis to produce novel oxindole analogues, including fluorinated ones. That’s the same structural tweak that turned kratom alkaloids into more potent derivatives like MGM-15 in the published literature. Nothing stops an unregulated chemist from doing that work and selling the result under the same “Cat’s Claw” name, so the realistic expectation for this product category isn’t one compound. It’s a moving target.
Risks that matter if you’re using one
- It’s an opioid, whatever the label says. Whether the active is corynoxine B, MGM-15, or an undisclosed synthetic, it’s a mu agonist producing dependence, tolerance, and classical opioid withdrawal.
- It won’t show on a standard drug panel. Probation, employment, and treatment-program tests aren’t looking for these compounds.
- You can’t dose it safely, because you don’t know what’s in it, how much, or how it clears. Batch-to-batch variation is real even within one brand.
Coming off one of these
You’re not the first person a deceptive label caught, and there’s nothing about “cat’s claw” that makes quitting different. If you stop and get hit with opioid withdrawal you weren’t expecting, that’s the agonist in the product, not the herb. “Cat’s claw withdrawal” isn’t a thing.
The paths off are the same as for any 7-OH-class product. Start with How to Quit 7-OH, or if you’re already in withdrawal, Withdrawal Help.