Plectranthus neochilus Schltr.: Anatomic and cytogenetic analyses and chemical characterization of its essential oil

Abstract

Although used for medicinal purposes, there are many inconsistencies in the literature regarding the identification of Plectranthus neochilus Schltr. due to the morphological similarities with other species belonging to the so-called “P. caninus complex”. Studies that develop tools for the correct identification of medicinal plants are of vital importance as the use of the wrong species can lead to serious health problems. Thus, the objective of the study was to determine a profile to identify individuals of P. neochilus based on anatomic, chemical and cytogenetic analyses. The cytogenetic analysis showed that all the individuals used in the present study belonged to the same species (2n = 30), P. neochilus, in agreement with literature. The presence of diacytic stomata, absence of digitiform trichome, distribution of peltate glandular trichomes on both sides of the leaves are also in agreement with previous reports for P. neochilus. However, the leaf mesophyll and the layout and morphology of glandular trichomes were different from those previously described in the literature. Histochemical tests showed the absence of phenolic compounds but presence of total and neutral terpenes and lipids. The essential oil obtained by hydrodistillation contained β-caryophyllene as the major compound (20.11%) which also coincides with other studies of P. neochilus in Brazil. These results show the cytogenetic, anatomical and the chemical profile of the essential oil of P. neochilus in Brazil and can be used as a tool for its identification.