Phytochemical screening, GC-MS analysis and antibacterial activity of Acanthus ilicifolius (L.) fruit extract

Acanthus ilicifolius is a mangrove plant that contains various bioactive compounds contributing to its pharmacological activities. While several studies have reported its antimicrobial efficacy, there is still a lack of research specifically investigating the antibacterial properties of its fruit. Therefore, this study was conducted to examine the phytochemical compounds in the methanolic extract of A. ilicifolius fruit using phytochemical screening assays and GC-MS analysis. The antibacterial activity was then determined using the agar well diffusion method, and minimum inhibitory concentration (MIC) was conducted using a 96-well resazurin assay. The presence of terpenoids, flavonoids, steroids, saponins and tannins were detected and ten major metabolites were found in the non-polar fractions namely benzophenone, toluene, phenol, n-Hexadecanoic acid, 2,4-bis (1,1-dimethylethyl), 2(3H)-benzoxazolone, hexanedioic acid, methyl ester, 9-Octadecenoic acid, methyl ester, (E), 9,12-Octadecadienoic acid (Z.Z), cis-Vaccenic acid and 13-Docosenamide, (Z). The extract exhibited the highest inhibitory activity against Escherichia coli (15.73 ± 0.33 mm), followed by Pseudomonas aeruginosa (15.10 ± 0.70 mm) and Staphylococcus aureus (13.13 ± 0.57 mm). Furthermore, the lowest MIC values against E. coli, P. aeruginosa and S. aureus were found at 3.13 mg/mL, 12.50 mg/mL and 12.50 mg/mL, respectively. These findings suggest the potential efficacy of A. ilicifolius fruit as an antibacterial agent and further studies should focus on the assessments of the cytotoxicity and safety profile of the fruit extract.