Phytochemical And Micro Anatomical Studies on Leaf, Stem and Petiole of Two Species of Dioscorea (Dioscorea alata L. and Dioscorea bulbifera L.)

Abstract

This study investigated the presence of bioactive compounds and micro anatomy on leaf, stem and petiole of Dioscorea species (Dioscorea alata and Dioscorea bulbifera). The phytochemical analysis revealed the presence of saponins, tannins, glycosides and absent of alkaloids, anthraquinone and phlobatanin in Dioscorea alata. Alkaloids, saponins, tannins, glycosides and flavonoids were present in Dioscorea bulbifera while anthraquinone and phlobatanin were absent. Microanatomical section of Dioscorea alata leaf showed amphistomatous epidermal cell with thickened cell wall and distinct middle lamella, bounded with intercellular air space, adaxial epidermal cells with eccentric nuclei, large central vacuole with thin peripheral layer of cytoplasm. The foliar epidermis of Dioscorea bulbifera leaf revealed anamocytic and anisocyticstomatas as well as dense hairy trichomes with cuticular striated cell wall on the adaxial and abaxial epidermis. Histological sections of Dioscorea alata stem revealed vascular bundles arranged in two concentric circles. The vascular bundle of the outer circle was smaller than the inner, with two metaxylem vessels together with one phloem unit present at both ends, however, the sections of Dioscorea bulbifera stem, showed bundles of inner circle with unpaired metaxylem with phloem unit at one end. Sections of Dioscorea alata’s petiole showed basically collateral vascular bundles arranged in a ring with the presence of two to three phloem units in each bundle with the presence of crystal granules. The sections of Dioscorea bulbifera’s petiole on the other hand showed longitudinal cell walls with the presence of sieve plates. These histological features and active compounds show that these plant parts are likely to have some medicinal compositions values that should be explored.