Freebase vs. salt-form MIT extract: which to buy.
Apricity supplies mitragynine (MIT) extract in two forms: freebase powder at 80%+ MIT by HPLC and salt-form powder at 75%+ MIT content by HPLC. Both ship in 1 kg units with a 10 kg minimum and an independent third-party COA on every lot. The right choice depends on your process, your product format and how you calculate label claims.
Freebase vs. salt: what's actually different.
Mitragynine is an indole alkaloid (C23H30N2O4, molecular weight about 398.5 g/mol) and a weak base. Published measurements put its pKa at about 8.1. In its freebase form the molecule is neutral and fairly lipophilic, with a reported logP of about 1.7. A salt forms when the base reacts with an acid. The nitrogen picks up a proton and pairs with the acid's counter-ion.
The alkaloid is the same either way. What changes is the powder's physical behavior: how it dissolves, how it takes up moisture, how it handles on equipment, and how much of each kilogram is mitragynine and how much is counter-ion.
Solubility
Freebase mitragynine is poorly soluble in water. In one peer-reviewed study it measured about 65 µg/mL in plain water at 37 °C; at pH 4 the same study measured about 3.5 mg/mL. Salt formation is one of the most common ways to raise the water solubility of a basic compound, so expect a salt-form powder to disperse and dissolve in water much more readily. Freebase is more at home in organic solvents and lipid-based systems.
Moisture and handling
Salts tend to be more polar than their freebase, and mineral-acid salts in particular can be more hygroscopic. A salt-form powder may need closer humidity control during storage, blending and compression; freebase is generally less sensitive. Flow depends as much on particle size, shape and moisture as on chemical form, so test the sample on your own equipment. The USP <1174> powder-flow tests (angle of repose, Carr index, Hausner ratio) give comparable numbers.
Stability
Peer-reviewed work describes mitragynine as acid-labile: it degrades over time at low pH, and under alkaline conditions its methyl ester can hydrolyze. Both pH and temperature affect stability. That matters most for water-based products, where the counter-ion and the formulation set the finished product's pH. Store dry powder sealed, cool, dry and out of light, and run stability testing on your finished format.
Comparison table.
The same alkaloid in two physical forms. Choose by process and format, then compare lots on the same basis.
| Freebase MIT extract | Salt-form MIT extract | |
|---|---|---|
| Apricity spec | 80%+ MIT by HPLC | 75%+ MIT content by HPLC |
| Chemical state | Neutral alkaloid | Protonated alkaloid plus counter-ion |
| Water solubility | Low | Higher, which is the usual reason to choose a salt |
| Organic and lipid systems | Generally compatible | Less suited |
| Moisture sensitivity | Generally lower | Often higher; control humidity |
| Fill weight per mg of MIT | Smaller | Slightly larger (counter-ion adds mass) |
| Typical formats | Compressed tablets, capsules | Water-based liquids, fast-dispersing formats |
| Key COA question | MIT % by HPLC | MIT % by HPLC, reported as MIT content |
How to compare % on a COA.
This is where buyers most often compare numbers that aren't on the same basis.
An HPLC assay measures mitragynine against a reference standard. A lab can then report the result in one of two ways:
- As freebase-equivalent MIT. This is the share of the powder's weight that is the mitragynine molecule itself.
- As the salt. This is the share of the powder's weight that is mitragynine plus its counter-ion.
Because the counter-ion adds weight, these two numbers aren't interchangeable. A figure reported as salt weight overstates the actual MIT content, by several percentage points or more depending on the counter-ion.
Pharmaceutical convention (FDA guidance and the USP salt-nomenclature policy) expresses strength in terms of the active moiety, the freebase, rather than the salt. Doing the same keeps your formulation math consistent across lots and suppliers.
When you review any MIT COA, ours included, check:
- Basis. Is the MIT figure reported as MIT content or as salt weight?
- Method. Is it HPLC, against which reference standard, and from which lab?
- Lot match. Does the COA lot number match the lot number on the unit?
- The full alkaloid panel. Look at 7-hydroxymitragynine as well as MIT. Our COAs also cover heavy metals and microbials.
- Actual vs. minimum. Work from the measured value on the lot's COA, not the "+" minimum in a product listing.
For tablet and capsule fill, divide your target MIT per unit by the COA's MIT fraction on the same basis your label uses, and recalculate for every new lot. Our tablet manufacturing guide works through an example.
Which form for which product.
The formulator makes the final call on form and fill. We supply the documentation and a sample so you can make that call with data.
Compressed tablets
Freebase is the usual starting point. It packs more MIT into each milligram of extract, leaving more room for fillers, binders, disintegrants and lubricants, and its lower moisture sensitivity makes blending and compression easier to control. Salt form works if your formulation calls for faster dispersion in water; allow for the larger fill weight and tighter humidity control. See kratom extract for tablet manufacturing.
Capsules
Freebase usually gets the most MIT into a given capsule size. Salt form is workable if your fill weight and the room's humidity allow for it. Either way, confirm flow on your encapsulator before committing to a full run.
Liquid shots and water-based formats
Salt form is the logical candidate because of its water solubility. Mitragynine's acid lability means the finished product's pH, ingredients and storage conditions all affect stability, so plan for compatibility and stability testing. Freebase can be used in solvent-, emulsion- or lipid-based systems, but that is formulation work, not a simple dissolve-and-fill.
Full specs for both forms are on our bulk kratom extract page.
FAQ.
Is the salt form a lower grade because it's 75%+ instead of 80%+?
No. Both figures are MIT content by HPLC. The salt form carries counter-ion weight, so each kilogram holds a little less MIT than freebase. That is chemistry, not grade.
Can I switch forms between production runs?
Yes, but treat it as a reformulation. Recalculate fill weights from the new COA, recheck flow and moisture behavior, and review your label against your compliance requirements.
Do you sell to consumers?
No. Apricity sells to businesses only. We don't ship to states or localities where kratom or its alkaloids are restricted. Buyers are responsible for their own labeling, claims and regulatory compliance.
Request the current COA and a sample.
Both forms are in stock in U.S. warehouses on the East and West Coasts, in 1 kg units with a 10 kg minimum order. Every lot has a traceable number tied to its third-party COA. Tell us your product format and target volume, and we'll send the current COA for the form you're considering and arrange a sample to test on your own equipment. Wholesale and B2B only.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.