Cenostigma bracteosum Hydroethanolic Extract: Chemical Profile, Antibacterial Activity, Cytotoxicity, and Gel Formulation Development.

Background:Cenostigma bracteosum (Tul.) Gagnon & G.P. Lewis (Fabaceae), popularly known as "catingueira", is a plant widely distributed in the Caatinga biome, which comprises 11% of the Brazilian territory. While this species is of interest given local knowledge, formal reports are lacking in the literature, warranting targeted investigation. This study aimed to prepare and characterize a hydroethanolic extract of C. bracteosum leaves, prepare carbopol gels containing the extract, and evaluate their cytotoxicity and antibacterial activity against Staphylococcus aureus and Escherichia coli. Methods: The initial extract was prepared in an ultrasonic bath using ethanol/water (70:30, v/v). The extract (1 mg/mL) was analyzed by liquid chromatography coupled with mass spectrometry (UHPLC-MS/MS). Carbopol-based gels containing 1% and 3% of C. bracteosum extract were prepared and characterized in terms of pH, conductivity, spreadability, and rheology. The cytotoxicity was determined by the MTT method using MC3T3-E1 pre-osteoblast cells and L929-CCL1 fibroblast cells. The antibacterial activity of the extract and gels was evaluated using the agar diffusion method against S. aureus and E. coli. Results: The C. bracteosum leaves extract demonstrated antibacterial activity against S. aureus and E. coli, were not cytotoxic for the assessed cells at concentrations up to 100 μg/mL, and its analysis by UHPLC-MS/MS allowed the annotation of 18 metabolites, mainly of the phenolic acid and flavonoids glycoside classes, together with a biflavonoid. The prepared gels remained stable over the 30-day post-production analysis period. Conclusions: These findings provide a better understanding of the chemical diversity of the secondary metabolites of a common Caatinga biome species-C. bracteosum-specifically present in leaves hydroethanolic extract and gel formulation adapted for skin application with activity against S. aureus.