Estudo morfoanatômico, histoquímico e fitoquímico do óleo essencial de Plectranthus Ornatus codd. (Lamiaceae).

Abstract

Plants have valuable chemical compounds that are fundamental for their survival and development, among them, essential oils (EOs), which are complex volatile substances, being a product of the secondary metabolism of plants. The species Plectranthus ornatus Cood, popularly known as boldo, belongs to the Lamiaceae family, one of the most requested by its EOs, having great medicinal, ornamental and economic importance, presenting morphological similarities with other species of this family and mainly of the genus Plectranthus. In this sense, the present research presents a study of morphoanatomical and histochemical analysis of the leaf blade and phytochemistry in the extraction of the essential oil of the species Plectranthus ornatus, aiming to provide morphological, anatomical, histochemical characteristics and to evaluate the chemical compounds of its foliar essential oil, describing characteristics for species identity. The collection points of Plectranthus ornatus were selected based on information from a small plantation in the municipality of Quatipuru and in the municipality of Barcarena in Pará, being collected and deposited in the herbarium of the Goeldi Museum - MPEG. The essential oil was extracted by the hydrodistillation method and stored in glass ampoules, and anatomical and histochemical analyzes were carried out in transverse and longitudinal sections from 08μm to 10μm to follow epidermal dissociation, diaphanization and tests with reagents to identify metabolite groups. The leaves of the specimens presented similar morphologies, differing only in size, presenting leaves as opposite cross, dentate margin, peninerveas, presence of trichomes, with very short petiole and flag-green color. In the anatomical study, numerous tector and glandular trichomes of different shapes and sizes were found, in addition to the identification of stellate trichomes, with epidermal cells on both sides of the leaves with sinuous anticlinal walls, amphistomatic leaf blade, diacytic stomata and subsidiary cells. In the oil extraction, a yield of 0.1 was obtained, which is considered low for the genus, with E-Caryophyllene as the major compound in the analysis of the essential oil, in which the histochemical tests found that this yield characteristic is due to the glandular trichomes that do not secrete only EOs, being mixed with resin, evidenced by the purplish coloration. In addition to positive reactions for total lipids and acids, terpenes, polysaccharides, phenolic compounds, tannins and alkaloids, and with the presence of calcium oxalate mainly in the petiole. The results obtained provided relevant information for the identification and quality control of the species, confirming its enriching potential as an aromatic plant for future studies.