Mitragyna speciosa Kratom leaf, Kratom leaf powder and extracts are best preserved in an cool environment where they are not exposed to air, humidity, heat or U.V. light.
One could say that the storing conditions of Kratom are similar to those that one would use for good tea leaves. An airtight environment, such as an opaque sealed box placed in the refrigerator would be recommendable for storing Kratom. A vacuum-sealer would also increase preservation further. Freezing Kratom products has also been recommended, when it is an option, especially for Kratom leaves or leaf powders. Traditionally, resinous extracts of Mitragyna speciosa Kratom are often covered in flour, which is thought to help isolate the resin from air and humidity.
A good idea is to divide one’s Kratom into small batches for storage, so that one does not have to reopen the storage container often, thus avoiding unnecessary exposure to air or moisture.
Properly stored Mitragyna speciosa Kratom has been said to keep its potency for decades.
Yet it has been suggested that in older Kratom, the mitragynine compound might progressively oxidate into mitragynine-pseudoindoxyl, which is said to act as a fairly selective δ-opioid agonist, with little affinity for μ or κ receptors. This might induce some change in the nature of old Kratom’s effect, but needs to be investigated further.