We analyzed the content of mitragynine (MG) found in kratom leaves (Mitragyna speciosa) and the influence of different environmental conditions (air and soil variables) on the yield in various regions of Thailand. The content of MG in kratom leaves ranged from 7.5 – 26.6 mg g^-1 of dry leaf weight. Canonical correspondence analysis showed that the most significant environmental variables affecting the MG content among the various regions were light intensity, relative humidity, soil volumetric water content (VW), soil pH, and calcium. This study is a first step towards providing information about environmental conditions suitable to maximize the quality and quantity of bioactive alkaloids in kratom. Future studies should focus on leaf collection and the post-harvest processes in order to assure the desired alkaloidal content in finished products, when produced under suitable environmental conditions identified in this study.

The cultivation of Mitragyna speciosa (kratom) has gained significant interest due to its diverse alkaloid profile, increasing its commercial and medicinal demand. Using controlled hydroponic techniques, this study investigates the effects of varying light intensity and water potential on kratom growth, mitragynine (MG) accumulation, and total alkaloid content (TAC). While the interaction between light and water potential was generally not significant, water potential emerged as the dominant factor affecting plant growth and alkaloid accumulation. The highest MG accumulation (0.63% w/w) was recorded under moderate water potential (−0.4 MPa). In contrast, the highest TAC (8.37 mg alkaloid equivalent per gram dry weight) was observed under the combined effect of low light and mild water potential (−0.4 MPa). Leaf age also played a key role, with younger leaves (second and third pairs) accumulating significantly higher MG levels (0.74% w/w) than older leaves (0.40% w/w). Additionally, leaf thickness was positively associated with MG levels, suggesting a potential link between plant morphology and alkaloid biosynthesis. However, low water potential (−0.7 MPa) significantly reduced both growth and MG content, highlighting the importance of optimizing environmental conditions for sustained bioactive compound production. These findings demonstrate the physiological adaptability of kratom to variable environmental stresses and their influence on alkaloid accumulation. This knowledge can be applied to precision cultivation strategies to enhance the sustainability of kratom farming while optimizing the production of bioactive compounds for pharmaceutical and agricultural applications.

Kratom leaves are widely consumed by locals to increase their stamina for working longer hours in the field. However, insect damage to the leaves can lead to significant loss of leaf harvest. Despite this, there remains considerable uncertainty regarding how herbivory attack affects the chemical composition of kratom’s leaf metabolome. In this study, we investigated the effect of insect herbivory on the secondary metabolites (SMs) of kratom leaves, using untargeted metabolomics as well as the effect on the accumulation of mitragynine and relation to leaf traits. The presence of diverse herbivore species were observed on the kratom leaves as indicated by three orders of insects including Coleoptera (beetles), Lepidoptera (butterflies and moths) and Hemiptera (true bug). A higher accumulation of mitragynine was observed as a defense mechanism against herbivores, with the study also finding a correspondence between increased mitragynine levels and elevated leaf acidity. A significant difference in the presence of three key metabolites (cearoin, 8-hydroxy-8-(3-octyloxiran-2-yl) octanoic acid, and 2,3,5,7-tetramethoxy-9,10-dihydrophenanthrene) that have interesting therapeutic usage, between insect and non-insect leaves, indicated the influence of interaction with insect herbivory. In conclusion, these findings highlight the potential to manage insect herbivory to modulate alkaloid accumulation in kratom, offering a sustainable approach that preserves insect biodiversity while naturally boosting the plant’s chemical defense.

Understanding interspecific and environmental influences on secondary metabolite profiles can be critical in plant metabolomics. This study used a hierarchical orthogonal projections to latent structure discriminant analysis (OPLS-DA) to classify the foliar metabolomes of four naturally growing Mitragyna species in Thailand, M. speciosa, M. diversifolia, M. hirsuta, and M. rotundifolia. Using a recursive binary classification, interspecific and environmental influences were determined in multiple class separations, while identifying key metabolites driving these distinctions. Gas chromatography–mass spectrometry (GC-MS) annotated 409 metabolites, and through a progressive class differentiation using hierarchical OPLS-DA, M. speciosa exhibited a metabolome distinct from the other three species. However, the metabolomes of M. hirsuta and M. rotundifolia had a lot of overlap, while M. diversifolia displayed regional metabolic variation, emphasizing the role of environmental factors in shaping its chemical composition. Key metabolites, such as mitragynine, isorhynchophylline, squalene, and vanillic acid, among others, were identified as major discriminators across the hierarchical splits. Unlike conventional OPLS-DA, which struggles with multiclass datasets, the recursive approach identified class structures that were biologically relevant, without the need for manual pairwise modeling. The results aligned with prior morphological and genetic studies, validating the method’s robustness in capturing interspecific and environmental differences, which can be used in high-dimensional multiclass plant metabolomics.

This study investigates how soil calcium (Ca) and magnesium (Mg) supplementation influence mitragynine accumulation in Mitragyna speciosa (kratom), addressing the lack of quantitative thresholds in previous research. Seedlings from a uniform seed stock were cultivated in a controlled environment using a standardized soil mix (soil:peat moss:earthworm castings, 6:1:1). Following an initial growth phase, Ca and Mg were applied at three concentrations and in fixed Ca:Mg ratios (5:1, 10:1, 20:1) using gypsum and Epsom salt. Over a 45-day treatment period, growth parameters and mitragynine levels were assessed one week after the final application. Seedlings under control had the highest total biomass (102.35 g), significantly exceeding both the Mg-only and Ca:Mg treatments (64–84 g), and values above the typical upper threshold of 20 did not suppress growth, as evidenced by unchanged root-to-shoot ratios across treatments. In contrast, mitragynine accumulation was the highest under moderate Ca:Mg ratios (8–10), exhibiting a 2–14% increase relative to the control, suggesting that production of this alkaloid is more sensitive to nutrient balance than overall growth. These findings underscore the importance of nutrient ratios, rather than individual nutrient concentrations, in regulating both vegetative development and alkaloid production in kratom. Maintaining an appropriate Ca:Mg ratio can support efficient seedling growth as well as maximizing mitragynine levels. Preliminary field trials over a span of one month indicate that field-grown seedlings exhibit a similar result with high growth and mitragynine content in soils having a Ca:Mg ratio of 1:10. Future studies should test these responses under field conditions and over longer growth periods.

Kratom (Mitragyna speciosa (Korth.) Havil.) is a tropical evergreen species native to Southeast Asia, widely recognized for its medicinal properties. Recent legal changes in Thailand permitting its cultivation and commercial use have increased interest in understanding the optimal conditions for its growth, particularly in regions beyond its native southern habitat. This study examined the leaf functional traits associated with kratom’s growth in the southern (native habitat), central, and northeastern regions of Thailand. Species adaptation was determined by analyzing variations in leaf functional traits across different environments. The results showed that the specific leaf area (SLA), leaf thickness, chlorophyll content (SPAD), and stomatal density (SD) did not exhibit any significant regional variations. However, the leaf pH, performance index (PI), and quantum yield (Fv/Fm) differed significantly across regions. The northeastern region had higher leaf pH and lower photosynthetic efficiency compared to the southern and central regions. Non-Metric Multidimensional Scaling (NMDS) ordination indicated that environmental factors such as elevation, light intensity, temperature, and soil water content significantly influenced leaf trait variability in the northeastern region. These findings demonstrate kratom’s ability to grow under diverse environmental conditions, potentially indicative of cultivation beyond its native range.