Pheophorbide A from Acrotrema agastyamalayanum: A potent antibiofilm agent targeting Proteus mirabilis.

The antibiofilm potential of the hexane extract of the rare and endangered endemic plant Acrotrema agastyamalayanum was determined against Proteus mirabilis. The biofilm-inhibitory activity of the hexane extract was evaluated by crystal violet quantification and light microscopy, which showed 89% inhibition at 11 mg/mL. The hexane extract exhibited 89% inhibition at 11 mg/mL as determined by crystal violet quantification and light microscopy. Pheophorbide A (PA), the active and most abundant chlorophyll derivative in the hexane extract, was identified based on its molecular ion fragmentation pattern using high-resolution liquid chromatography mass spectrometry (LC-MS/MS). PA exhibited concentration-dependent biofilm inhibition at 100 μg/mL and disrupted biofilm structure, leading to microcolony disintegration as observed under a microscope. PA significantly reduced the cell surface hydrophobicity (CSH) and extrapolymeric substances (EPS) secretion, underscoring its critical role in disrupting biofilm matrix and bacterial cell adhesion. This is the first study to report PA from A. agastyamalayanum with remarkable antibiofilm properties, highlighting its potential as a natural antibiofilm agent for controlling P. mirabilis infections.