Quantification and histochemical localization of secondary metabolites during development in Annona muricata L. (Annonaceae)

Abstract

Histolocalization and quantification of secondary metabolites established the occurrence of alkaloids, phenols and acetogenins in various plant organs of A. muricata at different stages of plant growth.Annona muricata L. possesses broad assemblage of ethno-pharmaceutical and therapeutic upsides ascribed to biosynthesis of secondary metabolites. Currently, the bioactivity is characterized by the production of acetogenins (ACGs), and also by the biosynthesis of alkaloids, primarily benzylisoquinolines derived from tyrosine and phenolic compounds. As a result of high variability of metabolite production in A. muricata, the present study evaluated the histochemical analysis of various plant parts at different developmental stages of growth. Presences of phytometabolites were determined using in-situ histochemical localization of alkaloids, phenolic compounds and acetogenins, while its estimation employing spectroscopic quantification techniques to understand structure, development, time-course deposition, content and distribution of secondary phytoconstituents. Study revealed distinct presence of secondary metabolites in cells and tissues of all plant organs in various intensities and patterns. Alkaloids and acetogenins occurred mostly in secretory cavities or idioblast cells while sparsely associated with other cells or tissues. Phenolic compounds emerged widely, with no confined distribution patterns occurring in storage cells and tissues. Quantitative analysis revealed highest accumulation of alkaloids, phenols and acetogenins in mature root-barks, mature unripe fruit rind and mature leaf respectively. Secondary metabolites generally occurred in young stages at low concentrations as compared to matured growth stages of plant parts. Such in-situ histochemical and biochemical approach will help in identifying the cells and tissues responsible for synthesis, storage and biological effects of potential secondary metabolites which could be further used for culturing and enhancing its production with biotechnological aids.