Pharmacobotanical study of Psychotria carthagenensis Jacq. (Rubiaceae), a species known as toxic and medicinal

Abstract

Psychotria carthagenensis (Rubiaceae), popularly known as “erva-de-rato”, is known as poisonous, and its leaves are used as a constituent of “ayahuasca”. An anatomical study of its leaves was carried out to define parameters to support its taxonomy and quality control of ethnodrugs. Transverse and paradermic sections of petioles and leaf blades were made following the usual techniques of botanical anatomy. All semi-permanent laminas were then analyzed and photographed by light microscopy. Leaf blades were also studied with the support of the scanning electron microscope. Psychotria carthagenensis has hypostomatic epidermis, 1-2-stratified, in cross section, with three types of stomata (paracytic, anisocytic and anomocytic), and predominantly straight anticlinal cell walls, in frontal view, and glandular-peltate trichomes on both surfaces, the cuticle is smooth and thickened. The leaf edges are acute, mesophyll dorsiventral with the palisade parenchyma 1-seriate, and spongy parenchyma 4-seriate. The midrib is flat-convex with 4 bundles; petiole is semicircular with lateral projections with 9 vascular bundles. Midrib and petiole have collateral vascular system. Anisocytic and anomocytic stomata, glandular-peltate trichomes, petiole with the central bundle invaginate at the end, the syntopism of epicuticular waxes are distinctive parameters for P. carthagenensis, which support the standardization of its leaves used as medicines, in addition to contributing to the systematic of the Psychotria genus.