Caracterização do processo de cultivo e obtenção de óleo essencial de Plectranthus amboinicus (Lour.) Spreng. com atividade antimicrobiana

Abstract

Plectranthus amboinicus (Lour.) Spreng., of the Lamiaceae family, is a plant species popularly known as thick-leaf mint, with antimicrobial potential. Considering the need to standardize phytotherapeutics from agronomic aspects to their production, this research aimed to determine the cultivation period and fertilization that would provide the essential oil (EO) from the leaves of this species with the best antimicrobial response. The cultivation occurred in the greenhouse of the Horta de Medicinal Plants of the Federal University of Maranhão, São Luís-MA, between 2018 and2019, involving two types of fertilization: mixed (bovine and poultry) -A and bovineB in four climatic periods (early rainfall-T1, heavy rainfall-T2, late rainfall-T3 and drynessT4). Soil fertility (FS) and leaf nutritional status (NF) were analyzed and the EOs were extracted by hydrodistillation with determination of their yields and chemical composition by gas chromatography coupled to mass spectrometry. The antimicrobial activity was performed by disc diffusion with the microorganisms of Candida albicans, C. parapsilosis, C. krusei, Staphylococcus aureus and Escherichia coli with determination of the minimum inhibitory concentration, minimum bactericidal concentration and minimum fungicidal concentration. The best FS and NF results were obtained with fertilizers B and A, respectively. Statistical analysis of the multivariate data was performed by determination of variance (ANOVA) and comparison of the treatments was by Student's t-test. Principal component analysis investigated the similarity between the components of the EOs in the treatments. The stations that most influenced changes in FS and NF were the periods T1 and T4, in which it was perceived that while T4 increased FS and reduced NF, T1 acted in the opposite way. The yields of the EOs ranged from 0.4-1.65%. The NF interfered in the chemical composition of the EO, also influenced by fertilization and the climatic period in the formation of constituents, such as caryophyllene and γ-terpinene, which had their concentrations altered. However, carvacrol always remained the majority in all treatments, varying only its content. The best antimicrobial activity of the EO was obtained at T1 with fertilization A against C. albicans, C. parapsilosis, and E. coli microorganisms, and with fertilization B, still at T1, against S. aureus; while T4 showed the best response against C. krusei in both types of fertilization. Thus, it was found that the dry period (T4) and the transition period, which covers the end of the dry season and the beginning of the rainy season (T1), in both types of fertilization tested, are the most suitable for obtaining essential oil from P. amboinicus for development of biotechnology products with antimicrobial action.