<![CDATA[Bacterial resistance to conventional antibiotics has become a major global health challenge, prompting the exploration of natural antibacterial agents derived from plant materials. Durian (Durio zibethinus Murr.) albedo, an abundant agricultural by-product, has received limited attention despite its potential as a source of bioactive compounds. This study aimed to determine the total phenolic and flavonoid contents of ethanolic durian albedo extract, characterize its functional groups using Fourier Transform Infrared (FTIR) spectroscopy, and evaluate its antibacterial activity against Staphylococcus aureus and Escherichia coli. Fresh albedo of the Montong cultivar was extracted by maceration using 96% ethanol. Total phenolic and flavonoid contents were determined using the Folin–Ciocalteu and aluminum chloride colorimetric methods, respectively. Functional groups were identified by FTIR spectroscopy, while antibacterial activity was assessed using the agar disc diffusion method at extract concentrations of 15%, 25%, 35%, and 45%. The extract contained 0.52 ± 0.06 mg GAE/g extract of total phenolics and 0.034 ± 0.001 mg QE/g extract of total flavonoids, indicating the predominance of phenolic compounds. FTIR analysis revealed characteristic functional groups associated with phenolic-rich phytochemicals, including hydroxyl, carbonyl, aromatic, and C–O groups. The extract exhibited concentration-dependent antibacterial activity, with the largest inhibition zones observed at 45% against S. aureus (15.6 ± 0.7 mm) and E. coli (12.4 ± 0.6 mm). The greater susceptibility of S. aureus suggests higher effectiveness against Gram-positive bacteria. These findings demonstrate that durian albedo possesses promising antibacterial potential associated with its phytochemical composition and support its valorization as a sustainable source of natural antibacterial agents.]]>
