Physical Characteristics and Antibacterial Activity of Leaf Extract Gel Bougainvillea glabra against Staphylococcus aureus andEscherichia coli

Abstract

Bacterial resistance to conventional antibiotics has driven the search for natural antibacterial agents. Paper flower (Bougainvillea glabra) leaves contain secondary metabolites such as flavonoids, tannins, saponins, alkaloids, and steroids/terpenoids that are potentially antibacterial, yet their application in topical gel preparations and the accompanying stability evaluation remain scarcely studied. This study aimed to formulate a gel from Bougainvillea glabra leaf ethanol extract and to evaluate its physical characteristics, stability, and antibacterial activity against Staphylococcus aureus and Escherichia coli. The extract was obtained by maceration with 96% ethanol, yielding 10.05%, and was formulated into four gels containing 0% (F0), 5% (F1), 10% (F2), and 20% (F3) extract. Physical evaluation showed that all formulas remained homogeneous and stable throughout six freeze-thaw cycles, with pH 6.19-7.35, viscosity 3,353-8,506 cPs, spread ability 5.43-7.21 cm, and adhesion time 2.34-8.61 seconds. Disc diffusion assays showed that F3 produced the largest inhibition zones, 9.85±1.33 mm against Staphylococcus aureus and 9.20±0.56 mm against Escherichia coli, although still lower than the positive control. Statistical analysis indicated that increasing extract concentration did not significantly change antibacterial activity among formulas. The Bougainvillea glabra leaf extract gel exhibited favorable physical characteristics and shows potential as a natural topical antibacterial candidate.