Caracterização, toxicidade, atividade antioxidante, antimicrobiana e antibiofilme do óleo essencial e extrato de Achyrocline flaccida

Abstract

Medicinal plants represent an important source of new molecules with diverse benefits and/or applications for human health. Even with the advancement of technologies, plants continue to be the best option for discovering compounds with potential antioxidant, anti-inflammatory and antimicrobial activity. This fact is extremely important knowing the evolution of microrganisms and their resistance to existing antimicrobial therapy. In this context, this study aimed to re-search the plant Achyrocline flaccida know as “marcela ou macela”, knowing its wide medici-nal use in South America. Knowing the few existing researches with this species, we sought to understand at first the chemical composition of both the essential oil and the aqueous extract. We performed in vitro and in vivo toxicity tests. In addition, we analyzed the antioxidant activ-ity, and antimicrobial activity against Mycobacterium massiliensis, M. abscessus, M. fortuitum, Pythium insidiosum and Aeromonas hydrophila, in addition to evaluating the antiofilm effect. The characterization of the essential oil was performed by high-performance gas chromatog-raphy and the extract was characterized by high-performance liquid chromatography. The ma-jor compounds of essential oil were α-pinene (41.10%) and caryophyllene (30.52%), while for the extract, the major components were 3-O-methylquercetin (22.50%), quercetin (18%), and luteolin (12%). Both the essential oil and the extract did not show toxicity in vitro and in vivo tests at the concentrations tested. The effects in reducing reactive oxygen species were promis-ing for both compounds. It was observed that the oil and extract are able to reduce reactive oxygen species to basal levels and are also able to reverse the action of juglone (pro-oxidant). The essential oil showed bacteriostatic effect against mycobacteria at concentrations ranging from 1500 to 3000 μg mL-1. However, the extract was more effective, presenting bacteriostatic and bactericidal effects at concentrations ranging from 1560 to 3000 μg mL-1. Perceptive the good antimycobacterial activity of the extract, its antibacterial and antibiofilm action against A. hydrophila was analyzed. Once again, the extract proved to be effective in inhibiting and killing this microorganism at a concentration of 5000 μg mL-1 and was also able to inhibit biofilm formation. Furthermore, the anti-Pythium insidiosum effect of the extract was verified. The extract was active promoting the inhibition and death of this oomycete, at concentrations rang-ing from 97 to 1562 μg mL-1. The good results found encourage us in the search for explanations about the action mechanisms of the essential oil and aqueous extract of A. flaccida, with the aim of developing in the future a possible herbal medicine for topical and/or systemic use to treat various complications caused by these microorganisms.