Journal Article

Thai Medicinal Flowers as Natural Antioxidants and Antibacterial Agents Against Pathogenic Enteric Bacteria: A Comparative Study of Mesua ferrea, Mammea siamensis, and Clitoria ternatea

Intachaisri, Varachaya, Inta, Angkhana, Suriyaprom, Sureeporn, Ngamsaard, Pornpimon, Tragoolpua, Yingmanee, Cheepchirasuk, Nitsanat

2025

Overview

Thai medicinal flowers, namely Mesua ferrea L. (Bunnak), Mammea siamensis T. Anderson (Saraphi), and Clitoria ternatea (Anchan) have long been valued for their traditional medicinal. This study investigated their phytochemical composition and bioactivities, with a particular focus on antioxidant and antibacterial properties. Methods: Ethanolic flower extracts were analyzed by high-performance liquid chromatography (HPLC) and liquid chromatography–mass spectrometry (LC–MS). Antioxidant activities were determined by DPPH, ABTS, and FRAP assays. Antibacterial activity against Escherichia coli, E. coli O157:H7, Salmonella Typhi, Shigella dysenteriae, and Vibrio cholerae were assessed by agar well diffusion, broth dilution methods, and time–kill assays. Biofilm formation, biofilm disruption, and bacterial adhesion to Caco-2 cells were evaluated. Morphological changes in E. coli O157:H7 were examined using scanning electron microscopy (SEM), and leakage of intracellular contents (DNA, RNA, proteins) were quantified. Results: HPLC analysis revealed the highest level of gallic acid in M. ferrea and quercetin in M. siamensis. LC–MS analysis identified fifteen putative metabolites across the flower extracts, including quercetin, kaempferol, catechin, and luteolin derivatives, with species-specific profiles. C. ternatea extract exhibited the greatest total flavonoid content and antioxidant activity. Among the extracts, M. ferrea exhibited the strongest inhibitory effect, with inhibition zone of 13.00–15.00 mm and MIC/MBC values of 31.25–62.5 mg/mL. All extracts exhibited time-dependent bactericidal activity, significantly inhibited biofilm formation, disrupted established biofilms, and reduced bacterial adhesion to intestinal epithelial cells. SEM revealed membrane disruption in E. coli O157:H7 and leakage of intracellular components. Conclusions: Thai medicinal flower extracts, particularly M. ferrea, possess strong antioxidant and antibacterial activities. Their ability to inhibit biofilm formation, interfere with bacterial adhesion, and disrupt bacterial membranes highlights their potential as natural alternatives for preventing or controlling enteric bacterial infections.

• Publisher: MDPI AG,Multidisciplinary Digital Publishing Institute (MDPI)
• Subject: Acids / Adhesion / Analysis / antibacterial / Antibacterial activity / Antibacterial agents / Antimicrobial agents / antioxidant / Antioxidants / Bacteria / bacterial adhesion / Bacterial diseases / Bacterial infections / Bactericidal activity / biofilm / Biofilms / Bioflavonoids / Catechin / Chemical composition / Cholera toxin / Chromatography / Clitoria ternatea / Comparative studies / Dilution / Disruption / Drug resistance / E coli / enteric pathogens / Epithelial cells / Epithelium / Escherichia coli / Flavones / Flavonoids / Flowers & plants / Food / Functional foods & nutraceuticals / Gallic acid / Herbal medicine / High performance liquid chromatography / Intracellular / Kaempferol / Leakage / Liquid chromatography / Mammea siamensis / Mass spectrometry / Mass spectroscopy / Membranes / Mesua ferrea / Metabolites / Natural & organic foods / Pathogens / Performance evaluation / Phytochemicals / Proteins / Public health / Quercetin / RNA / Scanning electron microscopy / Scientific imaging / Seeds / Thai medicinal flowers / Time dependence / Traditional medicine