A new study published in Frontiers in Plant Science is presenting a clearer picture of how post-harvest processing changes the plant’s chemistry. The researchers from University of Florida and Oregon State University compared kratom varieties grown in Hawaii and Malaysia to see how factors like withering time, drying temperature, and harvest season influence alkaloid profiles—particularly mitragynine and 7-hydroxymitragynine (7-OH).
The findings further confirm what many in the kratom community have suspected: how the leaves are handled after harvest has a major impact on their final composition. Allowing leaves to rest for around 12 hours before drying increased levels of mitragynine and related alkaloids, but longer withering didn’t continue to raise those levels. Drying temperature turned out to be even more important. Lower temperatures preserved more alkaloids, while higher heat degraded or transformed them. For one Malaysian variety, temperature was the most critical factor overall.
Researchers also observed that 7-OH levels remained very low in most samples but varied slightly depending on genetics, harvest season, and drying conditions. This supports the idea that 7-OH may form during drying or oxidation rather than being produced in large amounts by the plant itself. In a 2022 interview with Kratom Science, Dr. Chris McCurdy, a researcher listed on this study, said of 7-OH that his team found “hardly any detected in the plant,” but that it tends to appear more in dried or processed products. He suggested that much of what is measured in commercial or dried samples might come from oxidation, heat, light, or chemical transformations after harvest—not from significant synthesis in the living leaf: “We should be finding leaf material that has no detectable levels of 7-hydroxymitragynine to start with, because we believe that when it’s ingested into the body that the amount of 7-hydroxymitragynine that’s produced from mitragynine is sort of canceled out by the other alkaloids that are present, and that the pharmacological effect is not achievable that you see when you isolate 7-hydroxy by itself.”
Another notable point from the study challenges a common consumer belief: the color of kratom powder—red, green, or white—has little to do with its alkaloid makeup. The researchers found that color differences mostly result from processing techniques, not chemical content. In other words, two batches that look completely different may have nearly identical alkaloid profiles. Before kratom consumers began to be informed by growing science, a common saying that linked effects to the powder color was, “white for flight, red for bed, and green in between”. Many vendors, however, have tried to brand their products based on effects rather than the color of the actual powder.
Genetics also plays a part in alkaloid makeup of different kratom cultivars. Two were used in this study, called ‘Hawaii’ and ‘MR-Malaysian”. Some of the differences in cultivars were as follows:
Withering duration significantly influenced mitragynine concentration in ‘Hawaii’, whereas it had a minimal effect on ‘MR-Malaysian’. In contrast, drying temperature had a greater effect on ‘MR-Malaysian’ than on ‘Hawaii’…Mitragynine concentrations in ‘Hawaii’ were generally higher during summer, while concentrations in cultivar ‘MR-Malaysian’ tended to be higher during winter. A similar seasonal contrast was observed with 7-hydroxymitragynine, a key metabolite of mitragynine. In ‘Hawaii’, 7-hydroxymitragynine was detectable only during the summer, whereas in ‘MR-Malaysian’, it was detectable only in the winter. Additionally, the alkaloids corynoxine A and B were consistently detected in ‘MR-Malaysian’ but were undetectable in ‘Hawaii’ regardless of seasons. This suggests that potential genetic differences occur in the biosynthesis of bioactive alkaloid compounds. Furthermore, greater variability in alkaloid concentration was observed in ‘MR-Malaysian’ between seasons compared to ‘Hawaii’, indicating that ‘MR-Malaysian’ may be more sensitive to subtle environmental or seasonal fluctuations
The study went on to say that “kratom beverages consumed in Southeast Asia may often be derived from a mixture of genetically diverse leaves.”. In a 2022 interview with Kratom Science, Dr. Brian Pearson, one of the researchers of this study, explain to us about the variability of kratom tree genetics: “Trees that were on the same farm in Southeast Asia, with the same environmental conditions, same soil, the same practices, and yet [the trees] had very different profiles with respect to mitragynine. “
An ideal for the kratom industry, as it is for other industries that produce plants for psychoactive effects (like coffee, tea, or tobacco), would be to have standardized cultivars that produce a consistent level of alkaloids for consistent effects. In our interview, Dr. Pearson laid out the steps that would occur to produce standardized kratom plants for a more consistent product:
Step one, there’s going to be genetic variability in the plants so we have to eliminate genetic variability, which is actually relatively simple. We identify a plant that has certain characteristics we’re looking for. That could be a volume of leaf mass or a resistance to a pest or disease, and that’s where Dr. McCurdy and his team in Gainesville are so helpful because it is important to identify what alkaloids may be beneficial and those that are not, and that ultimately helps us select which plant or plants we want to move forward.
From that point we can get them into a tissue culture facility generally, where we can mass-produce millions of plant units a year that are hundred percent genetic clones every single time, so that eliminates genetic variability.
The last component is an environmental component. So even if we have a hundred percent perfect clones of each other, then it’s a matter of understanding how the environment influences that plant again in terms of growth and yield and herbivory and alkaloid synthesis. So once we understand the environment – the light, the heat, the water or lack of water, and water stress – once we understand that we can put together a protocol that would allow for essentially very, very uniform production of plants to try to produce that variability. I think that’s achievable because we already do that with other plants for other applications, and so it’s applying that formula to this as well.
For manufacturers, the study reinforces the need for standardized selecting, growing and post-harvest methods to produce consistent products. For regulators and testing labs, it provides data that could help explain why alkaloid levels vary so widely between samples. And for consumers, it’s a reminder that kratom’s potency and effects are shaped as much by drying and handling as by where it’s grown and the cultivar. Should standardization happen, kratom consumers will have more reliable and consistent products with consistent effects.