Farmacobotânica, composição química e atividade biológica do Picão-preto (Bidens subalternans DC.)

Abstract

Bidens subalternans, belonging to the Asteraceae family, is a herbaceous plant, popularly known as picão-preto. It is native to Brazil and widely distributed. Recognized for its invasion into agricultural areas and adaptation to adverse environments, it is part of the Bidens Complex, presenting challenges in accurate identification due to morphological similarities with other species of the genus, such as B. pilosa and B. alba. Despite its prominence as an invasive plant in agronomic studies, the literature on B. subalternans is limited. Rare ethnobotanical reports mention its use in treatments for hepatitis, inflammation, diabetes and wound healing. This study aimed to investigate the in vitro antimicrobial and antioxidant activity of ethanolic extracts from the aerial parts of B. subalternans collected after cultivation in a natural and controlled environment. In addition, chemical prospecting of ethanolic extracts, chemical profile analysis by APCI, toxicity assessment in relation to Artemia salina and pharmacobotanical study of the leaf blade were carried out. Antimicrobial activity was evaluated using the disk diffusion method, while antioxidant activity was determined using DPPH and ABTS radical assays, followed by quantification of total phenolic compounds using the Folin-Ciocalteau method. The results demonstrated that B. subalternans extracts presented antibacterial activity against Staphylococcus aureus (ATCC25923), Enterococcus faecalis (ATCC00531), Bacillus cereus (ATCC9634), Listeria monocytogenes (ATCC7644), Escherichia coli (ATCC10536), with minimum inhibitory concentration values (MIC) ranging from 300 to 500 μg.mL-1. With regard to phenolic compounds, the extracts showed significant levels of total phenolics, with values of 1,149 mgEAG.g-1 for the extract from the environment and 140.6 mgEAG.g-1 for the cultivated extract. In the DPPH assay, the IC50 values of the two extracts ranged from 85.8 to 30.57 mg.mL-1, with inhibition percentages of 69.1% and 12.5%, respectively. The results related to the ABTS radical were also promising, with values of 1,969.0 μMTrolox.g-1 and an inhibition rate of 99.2% for the environmental plant extract, and values of 1,855.1 μMTrolox.g-1 and 93.57% inhibition for the cultivated plant extract. Analysis of the extracts revealed the presence of several classes of secondary metabolites, such as saponins, tannins, phenolic substances, phenols and flavonols. Analysis of the chemical profile by APCI-MS identified compounds such as chlorogenic acid, caffeic acid, rutin and tricin hexoside, among others. In the pharmacobotanical study, the typical anatomical aspects of the leaves of the species B. subalternans were observed, including anomocytic and anisocytic stomata, palisade and lacunous parenchyma, and well-developed vascular bundles. Phenolic compounds, mucilages and lipid droplets were also observed in the mesophyll and trichomes. The presence of secondary metabolites with antioxidant and antibacterial activity indicates the therapeutic potential of B. subalternans. Considering that these results may result from synergy between the substances, carrying out isolation studies of secondary metabolites and pharmacological evaluations are essential. These additional steps will significantly contribute to further exploration of the therapeutic potential and safety associated with these extracts. These pioneering studies for the species can play a crucial role in future research, especially with regard to the development of the bioeconomy in the State of Roraima.