Preliminary Antibacterial Activity Against Staphylococcus epidermidis and Chemical Profile of Gracilaria caudata Crude Methanolic Extract

Abstract

Currently, the dilemma of antimicrobial resistance (AMR) worsens each year and poses a threat to global health. Macroalgae are potentially excellent sources of highly bioactive secondary metabolites, particularly useful for developing new functional ingredients, and might represent a promising reservoir of novel antimicrobial agents in the fight against AMR. This study was conducted to determine whether methanolic extracts from Gracilaria caudata (MeOHGc) macroalgae could serve as potential alternatives against human pathogenic bacteria. The antimicrobial activity of MeOHGc was evaluated using the agar disc diffusion method against gram‐positive Staphylococcus epidermidis and gram‐negative Escherichia coli. The chemical profile of the methanolic extract was assessed by qualitative phytochemical screening and gas chromatography–mass spectrometry (GC/MS) analysis. The results of phytochemical tests revealed the presence of sterols, terpenoids, tannins, and polyphenols. The GC‐MS profile of MeOHGc putatively identified two chemical constituents based on the pre‐established similarity index threshold (SI ≥ 90%): benzenepropanoic acid, 3,5‐bis (1,1‐dimethylethyl)‐4‐hydroxy‐methyl ester (SI: 96.8%) and phenol, 2,4‐bis (1‐methyl‐1‐phenylethyl)‐ (SI: 96.8%). The antimicrobial activity assay showed preliminary antibacterial activity against S. epidermidis at the tested concentrations, with no activity detected against E. coli. Our results place G. caudata as a potential source worth investigating for the development of new antimicrobial agents, and open perspectives for its further investigation as biomolecular sources of these compounds.