Environmental Influence on the Untargeted Foliar Metabolome of Naturally Growing Mitragyna Species in Thailand

ABSTRACT This study investigates the foliar secondary metabolite profiles of four Mitragyna species naturally occurring in Thailand: M. diversifolia , M. hirsuta , M. rotundifolia , and M. speciosa (kratom). Using untargeted gas chromatography–mass spectrometry (GC–MS), 409 secondary volatile metabolites were annotated across the four species. M. diversifolia exhibited the highest number of detected volatile metabolites (87 ± 7), followed by M. hirsuta (75 ± 7), M. rotundifolia (74 ± 15), and M. speciosa (49 ± 11). Despite its lower overall metabolite count, M. speciosa had the highest number of unique compounds distinguishing it from the other species. Ten key volatile metabolites, including mitragynine, speciogynine, speciociliatine, paynantheine, isopaynantheine, and ajmalicine, were identified as major discriminants by Partial Least Squares Discriminant Analysis (PLS‐DA). Leaf traits such as chlorophyll content and leaf pH showed positive correlations with metabolite abundance ( r = 0.49 and 0.47; p ‐value < 0.0001), while specific leaf area showed a negative correlation ( r = −0.51; p ‐value < 0.0001). Constrained ordination indicated that T max (28.04%), vapor pressure deficit, drought, and wind (13.56%) significantly influenced metabolite composition ( p ‐value < 0.001). Given the presence of isomeric volatile metabolites, compound identifications remain putative and will require confirmation through targeted analyses using authenticated standards and orthogonal techniques. These results highlight distinct metabolomic signatures among Mitragyna species and provide a foundation for further research and exploration of these species in various scientific and medicinal contexts.