Bioactive potential of <i>Rhizophora apiculata</i> : phytochemical profiling, antibacterial activity, and toxicity evaluation on zebrafish ( <i>Danio rerio</i> ) larvae

<i>Rhizophora apiculata</i>, a mangrove plant, is recognised as a rich source of bioactive compounds with significant medicinal and pharmacological potential. This study aimed to investigate the phytochemical composition, antibacterial activity, zebrafish toxicity and promising bioactive constituents of <i>R. apiculata</i> ethanolic extract through Gas Chromatography-Mass Spectrometry (GC-MS) analysis and Fourier-Transform Infrared (FTIR) spectral analysis. Qualitative phytochemical screening results revealed the presence of alkaloids, saponins, phenols, glycosides, steroids, and tannins. GC-MS analysis identified a total of 12 compounds, encompassing antioxidants, fatty acids, esters, and steroidal ketones, while FTIR affirmed the presence of functional groups (-OH, -NH₂, C = O and -COOH) associated with antibacterial activity. The extract displayed significant antibacterial effects against oral pathogens, showing the highest activity against <i>K. pneumoniae</i>. The biosafety of the extract was assessed by exposing it to adult zebrafish larvae, and no acute toxicity was exhibited, suggesting it is safe for instant use. Overall, this report underscores <i>R. apiculata</i> crude extract to be a promising antibacterial agent against <i>K. pneumoniae</i>.