Composição química, avaliação da atividade antimicrobiana e antioxidade do óleo essencial e extratos vegetais das folhas de Myrcia palustris DC

Abstract

It is extremely necessary to search for new products from natural sources that can replace the synthetics that are widely used in industries, Brazil, for having the greatest biodiversity in the world, makes its species an alternative in the search for bioactive molecules in the search for new antimicrobials and antioxidants that are natural. Known as “pitangueira-do mato”, M. palustris belongs to the family Myrtaceae, a native species found mainly in southern Brazil and does not present studies on its biological activities. Therefore, the objective of this work was to determine the chemical composition of the essential oil of M. palustris by gas chromatography coupled to mass spectrometry (CG-EM), perform phytochemical prospecting using colorimetric tests of six extracts obtained from the leaves of M. palustris, namely: ethyl acetate (AcEt), acetone (AcOH), aqueous (EAq), ethanolic (EtOH), methanolic (MeOH ) and hexanic (Hex); to evaluate the antimicrobial activity of essential oil and plant extracts by the broth microdilution technique, using bacteria of medical interest, and the detection of the antioxidant potential by the 2,2-diphenyl-1- picryl-hydrazil (DPPH) technique. The total yield from the extraction by the essential oil hydrodistillation technique was 0.35%. CG-EM revealed the presence of 28 compounds, representing 80.75% of the essential oil, the majority being from the sesquiterpenes class. Regarding plant extracts, the tests showed the presence of compounds from the classes: steroids, flavonoids. Xanthones and tannins. The antimicrobial activity of the essential oil was observed for all Gram-positive bacteria (B. subtilis, E. faecalis and S. aureus) with the exception of S. epidermidis, among the Gram-negative bacteria, inhibitory activity was found only for S. flexeri and for yeast C. albicans, no inhibitory or fungicidal activity was observed. Regarding plant extracts, all showed antimicrobial potential against the strains tested, except for Hex extract, which showed no activity on K. pneumoniae. EAq showed the lowest efficiency for most strains tested. For antioxidant activity, the essential oil showed a DPPH radical reduction capacity of up to 82.81%, confirming its antioxidant potential. With the exception of EAq, all other extracts showed antioxidant potential in the highest concentrations tested in the range of 0.1 to 25 mg / mL; EtOH (82.29%), MeOH (77.67%) and AcOH (74.10%) showed greater capture of DPPH radicals. It is suggested that the antimicrobial and antioxidant activity of plant extracts and essential oil of M. palustris is related to the secondary metabolites present: steroids, flavonoids, xanthones and tannins, which have already shown these biological activities proven in other studies with plant extracts and due to the presence of the major compounds α-Guaieno (25.89%), α-Bulnesene (13.39%) and β-Selinene (4.76%).