ÓLEO ESSENCIAL DAS FOLHAS DE Psidium guajava: CONTROLE DE Sclerotinia sclerotiorum EM SOJA, ATIVIDADE BACTERICIDA E ANTICARIOGÊNICA

Abstract

The genus Psidium belonging to the family Myrtaceae comprises several important species, such as guava (Psidium guajava L.). The essential oil (EO) from leaves of this plant, has led to several studies due to its chemical composition and properties, highlighting its antimicrobial activity, and antifungal action. This has been proven on phytopathogenic fungi such as Sclerotinia sclerotiorum, which causes the white mold disease, which is one of the most important in soybean crop and also of difficult control. Once installed in the field, it is difficult to eradicate. The objective of this work was to test the EO of Psidium guajava leaves as emulsion and to determine its fungicidal effect on control of fungus Sclerotinia sclerotiorum in vivo in soybean, as well as to evaluate its anticaryogenic and antitumor activity. EO extraction was performed by hydrodistillation and its composition analyzed by GC-MS. For the EO application on the microorganism, two vehicles were used, emulsion and by microcapsules at 300 µl.mL-1. The in vivo test on soybean plants was performed using the emulsion over 7 mm Sclerotinia sclerotiorum fungus discs, which were incubated at 22 ºC and 90% RH and observed until the total negative control growth. As negative control, only the untreated fungus was used and, as positive control, the frowcide fungicide. The detached leaf test was performed following the same methodology as described for the in vivo test for both emulsion and microcapsules. The major EO compounds were trans-caryophyllene and α-humulene. The microcapsules in the detached leaf test allowed 34.6% white mold mycelial inhibition rate, while the emulsion allowed 96.4% and 92.5% in vivo test in soybean plants, proving its antifungal potential. Secondly, the EO anticancer activity of P. guajava leaves was determined in terms of their minimum inhibitory concentrations (MIC) using the broth microdilution method in 96-well microplates. The EO of Psidium guajava leaves had moderate activity against Streptococcus mutans (MIC = 200 μg / mL), S. mitis (MIC = 200 μg / mL), S. sanguinis (MIC = 400 μg / mL), S. sobrinus ( MIC = 100 μg / mL) and S. salivarius (MIC = 200 μg / mL). Antiproliferative activity was evaluated in tumor cell lines: breast adenocarcinoma (MCF-7), human cervical adenocarcinoma (HeLa) and human gliobastoma (M059J). A normal human cell line (GM07492A, pulmonary fibroblasts) was included. Antiproliferative activity was evaluated using the XTT assay and results expressed as IC50. The MCF and MO59J lines showed lower IC50 values than those obtained for the normal line, showing selectivity. These results suggest that EO Psidium guajava L. has promising biological activities and may be considered a new source of bioactive compounds.