Leaf anatomy and histochemistry of Oriza (Pogostemon cablin Beth., LAMIACEAE): Medicinal plant used in community Arari region, Itacoatiara, Amazonas

Abstract

Lamiaceae (Labiatae) is one of the largest Angiosperm families (with over 7500 species). Many authors confirm that 25 species from this family are medicinal, both native from Brazil and exotic. This work aimed to characterize the anatomy and histochemistry of the leaves of Oriza (Pogostemon cablin) and identify the key substances of pharmacological importance present in the leaves. The leaves were collected in the Monte Cristo community, Itacoatiara, and were studied via light microscopy and scanning electron microscopy (SEM), following standard anatomy and histochemistry protocols. For electron microscopy, sections were dehydrated in ethanol at different concentrations, undergoing critical point, metallization and then photomicrographed with the SEM. The front view epidermis appeared anfi/hypostomatic (but functionally hypostomatic) with diacytic stomata. The mesophyll is dorsiventral, with palisade parenchyma in a single layer of cells and the spongy parenchyma with 4 or 5 layers, witch two are maiden of parallel cells and the others are irregular. Petiole is non-cylindrical, with a semicircular arrangement of woody fascicles. Histochemically slices reacted to pectin, starch, proteins and phenolic compounds, tannins, acidic lipids, so that oriza showed all the substances assessed in the tests. The presence of the recorded compounds and the anatomical characterization may assist taxonomic pharmacological and allelopathic studies.