# Phytochemical Evaluation of Terminalia catappa L. Extracts with Antibacterial and Antibiotic Potentiation Activities Against β-Lactam Drug-Resistant Bacteria

## TL;DR

This study explores the antibacterial potential of Terminalia catappa extracts, especially against drug-resistant bacteria, and identifies key phytochemicals like flavonoids.

## Contribution

The study evaluates T. catappa's antibacterial activity and antibiotic potentiation against β-lactam-resistant bacteria, a previously underexplored area.

## Key findings

- T. catappa methanolic extract inhibited all tested bacterial strains, with strong activity against E. coli.
- Combinations of T. catappa extracts and antibiotics showed potentiated inhibitory effects.
- LC-MS identified flavonoids like rutin, quercetin, and ellagic acid in the extracts.

## Abstract

Terminalia catappa L. (Family: Combretaceae) is used globally to treat various diseases, including bacterial infections. Whilst the antibacterial activity of T. catappa has previously been tested against antibiotic-sensitive bacterial strains, the antimicrobial activity against methicillin and β-lactam-resistant pathogens has been relatively ignored. The antibacterial activity of T. catappa extracts, both alone and combined with selected clinical antibiotics, was evaluated in this study. The inhibition of bacterial growth by the extracts was determined using agar diffusion and broth micro-dilution assays. Combinations of the extracts and several clinical antibiotics were also examined and the ∑FICs were calculated to determine the interaction class. Synergistic combinations were further evaluated by isobologram analysis. The T. catappa leaf extracts were screened for toxicity using Artemia franciscana lethality bioassays (ALA). Orbitrap liquid chromatography–mass spectrometry (LC-MS) profiling analysis was undertaken to identify flavonoid components of the extracts, putatively. The T. catappa methanolic extract inhibited all the tested bacterial strains. It displayed especially good inhibitory activity against E. coli (MIC = 130 µg/mL). Combining the T. catappa extracts with some conventional antibiotics potentiated the inhibitory activity of the combinations compared to the activity of individual components. LC-MS profiling analysis identified multiple flavonoid components, including rutin, quercitin, orientin, the tannin component, and ellagic acid in the extracts. All extracts were non-toxic against Artemia nauplii. The phytochemical constituents present in the T. catappa leaf extracts warrant future investigation as potential antibacterial agents.