Secretory structures and histochemistry of roots, stem, and leaves of medicinal plant <i>Fibraurea tinctoria</i> Lour

Fibraurea tinctoria Lour. (Menispermaceae) is a medicinal plant used by many local tribes in Indonesia and other countries. This species has pharmacological potential, such as antimalaria, antibacterial, antitumor, antioxidant, anticancer, antidiabetic, anti-inflammatory, and hepato-protector. However, the secretory structures and sites of secondary metabolite accumulation still need to be studied. This study aimed to explore the secretory structures and reveal the accumulation sites of the main classes of secondary metabolites in the root, stem, and leaves of F. tinctoria. Histochemical analysis using various specific reagents was performed on freehand sections of the fresh organs to detect alkaloids, phenolics, terpenoids, and lipophilic compounds. Observations of secretory structures were carried out using light microscopy. The result showed that idioblast was the predominant secretory structure in the plant organs and contained all the chemical groups investigated, while laticifer accumulated alkaloids were found only in the stem. Some secondary metabolites were localized in the xylem, intercellular space, and cuticle layer. Crystals were observed in the root, stem, and leaf of this species. These results might be helpful as guide information for extracting the particular plant parts to obtain the desired secondary metabolites. It suggested that leaves are a potential alternative source of medicinal raw material of this species, in addition to the stem. RESEARCH HIGHLIGHTS: The first study on secretory structures of Fibraurea tinctoria. Secondary metabolites in F. tinctoria organs accumulate in specialized and unspecialized structures. The idioblast is the primary secretory structure in the organs of F. tinctoria spreading over the root, stem, and leaves.