Caracterização química e bioatividade do extrato das folhas de Baccharis punctulata (Asteraceae)

Abstract

Baccharis punctulata DC. (Asteraceae), popularly known as “chirca-do-mato,” is a species native to South America, widely distributed in Argentina, Bolivia, Uruguay, Paraguay, and Brazil, where it occurs mainly in the Southern and Southeastern regions. The species is traditionally used by rural communities, especially in Bolivia, for different therapeutic purposes, which has stimulated growing scientific interest. The present study aimed to chemically characterize the leaf extract of B. punctulata collected in Brazil and to investigate its biological activities, seeking to establish correlations between chemical composition and activities of agronomic and health-related interest. The leaves were subjected to acid–base extraction using solvents such as chloroform, ethyl acetate, and methanol, and the extraction process was monitored by thin-layer chromatography. The extract (BP4), obtained with ethyl acetate at pH 4, was selected for chemical characterization by highperformance liquid chromatography coupled to high-resolution mass spectrometry and for biological assays due to its higher yield. Chemical analysis revealed a predominance of phenolic acids (57%), followed by flavonoids (15%) and coumarins (9%), in addition to other classes of metabolites present in lower proportions and compounds reported for the first time in the species. The BP4 extract exhibited antibacterial activity with minimum inhibitory concentrations of 1.25 mg/mL against Bacillus subtilis INCQS 00002, 2.5 mg/mL against Staphylococcus aureus BEC9393 (MRSA), and 5 mg/mL against Staphylococcus aureus N315 (MRSA). The allelopathic activity of BP4 was evaluated through germination and early growth assays, in which the germination speed index (GSI) and germination percentage (GP%) of Lactuca sativa L. and Eleusine indica L. seeds were determined, as well as root and shoot growth of seedlings subjected to extract treatment. The results showed that root growth of L. sativa seedlings was significantly reduced starting at a concentration of 2 g/L, whereas the shoot exhibited greater sensitivity, with significant reduction at 1 g/L. In E. indica, the BP4 extract reduced early growth of both roots and shoots from 1 g/L onward, with total inhibition of seedling development observed at 4 g/L. The GP% of L. sativa seeds did not show significant differences compared with the control at any of the evaluated concentrations. In contrast, E. indica seeds showed a significant reduction in GP% at all tested doses, reaching 95% inhibition at 4 g/L compared with the control. These results highlight the antibacterial and allelopathic potential of the BP4 extract, reinforcing the relevance of B. punctulata as a source of bioactive metabolites. Furthermore, the study is aligned with the Sustainable Development Goals (SDGs) by encouraging the rational use of natural resources and contributing to sustainable development in the face of current challenges in health and agricultural production.