Estudo dos compostos fenólicos das folhas e frutos de Lantana trifolia L.(Verbenaceae)

Abstract

Lantana trifolia L., popularly known as “milho de grilo” is a shrub plant used in folk medicine to treat flu, asthma, and as sedative. Chemical studies of the leaves of this plant reported the presence of phenolic compounds. In this context, the presente study aimed to study the phenolic compounds of L. trifolia leaves and fruits collected in Peirópolis/MG and Pontal/SP, and then evaluate the antioxidant and antimicrobial activities of fractions from liquid-liquid extraction. The ethyl acetate and n-butanol fractions presented phenolic compounds in higher levels except for the Peirópolis leaves, where the ethyl acetate and hydromethanolic fractions presented these compounds in higher amounts. The more polar fractions of leaves and fruits from both locations presented lower values of EC50 (higher antioxidant potential), a fact that may be justified by the presence of phenolic compounds. In the assay for antibacterial activity it was observed that the FoPoHex and FoPeAcOEt fractions showed moderate activity (MIC 200 μg/mL for Aggregatibacter actinomycetemcomitans) and the FoPeAcOEt fraction showed moderate activity against Streptococcus mitis (CIM 200 μg/mL). In the antifungal assay it was observed that the ethyl acetate fractions showed MIC values lower than 100 μg/mL for the three Candida strains evaluated (C. albicans, C. tropicalis and C. glabrata), with emphasis on FrPoAcOEt, FrPeAcOEt and FrPenBut fractions who presented MIC values of 1.46, 2.93 and 2.93 μg/mL, respectively, against C. glabrata, close to the amphotericin B used as positive control (0.5–1.0 μg/mL). Along with the cytotoxicity results, the selectivity indexes were evaluated, and analyzing the values obtained was concluded that the most active fractions in the antifungal assay were more selective against C. glabrata than healthy cells. The ethyl acetate and n-butanol fractions of leaves and fruits were subjected to analysis by high performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) from which was possible to identify fifteen phenolic compounds, of which ten are being reported in the plant for the first time. Using semi-preparative HPLC it was possible to isolate the major compound verbascoside that the structure was elucidated by MS and NMR spectroscopy.