Ex situ cultivation effects on growth performance and secondary metabolite profiles of Securidaca longipedunculata (Polygalaceae) in DRC

Abstract S. longipedunculata Fresen (Polygalaceae) is a medicinal tree widely exploited across sub-Saharan Africa, particularly in the miombo woodlands of southeastern Democratic Republic of Congo (DRC), where increasing harvesting pressure threatens its persistence. This study evaluated the effects of ex situ cultivation under Lubumbashi (Upper Katanga, DRC) conditions on both growth performance and secondary metabolite profiles, with the aim of assessing domestication potential for conservation and sustainable use. A field experiment was conducted at the University of Lubumbashi using a completely randomized design with four substrate types (sawdust, sand, forest litter, and agricultural soil), each replicated fifteen times. Growth parameters (survival rate, plant height, leaf number, and collar diameter) were monitored over 18 months. In parallel, thin-layer chromatography (TLC) was employed to qualitatively compare major phytochemical groups (alkaloids, terpenoids, flavonoids, and phenolic acids) in roots, stems, and leaves from both wild and cultivated plants collected in the Lubumbashi region. Substrate type significantly influenced seedling establishment. Sawdust resulted in the highest survival rate (70%), while forest litter promoted superior growth, likely due to enhanced nutrient availability and improved physicochemical properties. Phytochemical screening revealed a consistent presence of flavonoids and phenolic acids in leaves and young stems across both wild and cultivated samples, highlighting their potential as alternative medicinal organs. Terpenoids were mainly detected in roots and stems, in agreement with traditional uses in the region. Alkaloids were not detected, possibly due to methodological limitations or environmental variability affecting their expression. Importantly, chromatographic profiles showed strong similarity between wild and cultivated plants, indicating that ex situ cultivation under Lubumbashi conditions does not significantly alter the qualitative composition of secondary metabolites. These findings support the integration of S. longipedunculata into agroforestry and restoration programs in southeastern DRC, providing a viable pathway for biodiversity conservation and sustainable medicinal plant use.