Medicinal plants have traditionally been used to treat various human diseases worldwide. In this study, we evaluated the leaf extracts of plants from the Acanthaceae family, specifically Clinacanthus nutans (Burm.f.) Lindau, Thunbergia laurifolia Lindl., and Acanthus ebracteatus Vahl., for their compounds and antioxidant activity. The ethanolic extracts of A. ebracteatus showed the highest total phenolic content at 22.55 mg GAE/g extract and the strongest antioxidant activities, with IC₅₀ values of 0.24 mg/mL and 3.05 mg/mL, as determined by DPPH and ABTS assays. The antibacterial efficacy of these extracts was also tested against Streptococcus pyogenes, Streptococcus mutans, Staphylococcus aureus, and Klebsiella pneumoniae. The diameters of the inhibition zones ranged from 14.7 to 17.3 mm using the agar well diffusion method, with MIC and MBC values ranging from 7.81 to 250 mg/mL. Anti-biofilm formation, antibacterial adhesion, and antibacterial invasion assays further demonstrated that these medicinal plant extracts can inhibit bacterial biofilm formation and prevent the adhesion and invasion of oral pathogenic bacteria on the human tongue squamous cell carcinoma-derived cell line (HSC-4 cells). The ethanolic extracts of C. nutans and A. ebracteatus were able to inhibit the gtfD and gbp genes, which facilitate biofilm formation and bacterial adherence to surfaces. These findings provide new insights into the antibacterial and antioxidant properties of plant extracts from the Acanthaceae family. These activities could enhance the clinical and pharmaceutical applications of plant extracts as an alternative therapy for bacterial infections and a dietary supplement.

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.

Propolis is a resinous natural product collected by bees from plant sources to protect the hive. Its chemical composition varies according to bee species and environmental conditions, resulting in differences in its biological activities. This study aimed to evaluate the biological properties of stingless bee propolis collected from different provinces in Thailand, with particular attention to two native species, Tetragonula pegdeni and Tetragonula laeviceps. These two species of Tetragonula are commonly found in tropical regions of the country. The investigation focused on their antioxidant, antimicrobial, and anti-inflammatory activities. The propolis extract from T. laeviceps stingless bee (sample D) exhibited the highest total phenolic and flavonoid contents, at 29.59 mg GAE/g extract and 73.95 mg QUE/g extract, respectively. Among the propolis extracts, T. pegdeni stingless bee propolis extract (sample A) showed the greatest antioxidant activity of 7.08 ± 0.18 GAE/g extract and 75.64 ± 3.07 mg TEAC/g extract by the DPPH and ABTS assays, respectively, together with the highest FRAP value of 48.54 ± 0.48 mg FeSO₄/g extract. The antibacterial efficacy of these extracts was further evaluated against skin pathogenic bacteria, including Staphylococcus aureus, Staphylococcus epidermidis, methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Micrococcus luteus, and Cutibacterium acnes. Inhibition zones ranged from 7.00 to 14.00 mm when determined by the agar disc diffusion method. Moreover, antibacterial activity was investigated by broth dilution assay, and MIC and MBC values ranged from 0.97 to 125 mg/mL. The cytotoxicity test of propolis extracts using RAW264.7 macrophage cells showed cell viability above 70%, and the selected concentrations were used for further anti-inflammatory evaluation. T. pegdeni stingless bee propolis extracts (samples A and B) demonstrated anti-inflammatory activity by reducing NO production and decreasing the expression of iNOS, COX-2, and IL-1β genes in LPS-stimulated RAW264.7 macrophage cells. LC–MS analysis revealed differences in chemical profiles among the propolis extracts and various bioactive compounds, including phenolic acids, flavonoids, xanthones, terpenoids, triterpenoids, and curcuminoids were identified. Therefore, Thai stingless bee propolis demonstrated potential as a natural source of bioactive compounds with antioxidant, antibacterial, and anti-inflammatory properties.