Antibacterial and antioxidant activity of the extract and fractions of the aerial parts of Richardia brasiliensis

Abstract

The Richardia brasiliensis species is an invasive plant used in folk medicine and due to its chemical characteristics, studies were carried out to determine its antibacterial and antioxidant activity, using extract and fractions of the aerial parts (leaves and stems). The ethanolic extract (ExEtOH) and the hexane (FHex), ethyl acetate (FAcoet) and hydromethanolic (FH/MeOH) fractions were subjected to chemical analysis and determination of their antioxidant and antibacterial potential. The phytochemicals with the highest frequency (100%) were flavonoids (ExEtOH, Fhex, FAcoe and FH/MeOH), phenolic compounds (ExEtOH, FAcoe and FH/MeOH), tannins (FH/MeOH), triterpenes (ExEtOH and FAcoe) and steroids (ExEtOH and Fhex). The content of phenolic compounds (C.F.) and total flavonoids (F.T.) were higher for FAcoe (C.F.= 798.5 μg/g and F.T.= 253.4 μg/g), followed by ExEtOH (C.F.= 685.3 μg/g; F.T.= 195.7 μg/g), FH/MeOH (C.F.= 347.5 μg/g; F.T.= 23.1 μg/g) and FHex (C.F.= 124.0 μg/g; F.T.= 63.1 μg/g). FAcoe and FHex showed greater antioxidant activity and the ExEtOH extract (14.5 mm) and FHex fraction (15.3 mm), showed a halo of moderate inhibition against Staphylococcus aureus at the lowest concentrations, with only the FHex and FAcoet fractions demonstrating effect against S. aureus with broth microdilution values of 6.25 to 12.5 mg/mL. The results indicated the presence of phytochemicals with antimicrobial potential in these two fractions, indicating a possible source of obtaining herbal medicines to treat infections, thus justifying the ethnic uses of R. brasiliensis for various infectious diseases.