In vitro Antioxidant and Antimicrobial Activities of Euphorbia thymifolia Extracts and Development of an Experimental Oral Rinse

Abstract

Aims: Oral diseases are associated with complex microbial biofilms and oxidative inflammatory processes. This study evaluated the phytochemical profile, total phenolic content, DPPH radical-scavenging activity, and preliminary antimicrobial activity of aqueous and hydroethanolic extracts of Euphorbia thymifolia and examined the activity and quality attributes of experimental oral-rinse formulations. Methodology: Aqueous and hydroethanolic extracts were subjected to qualitative phytochemical screening and determination of total phenolic content. Antioxidant activity was assessed by the DPPH assay. Agar well diffusion was used as a preliminary screening method against Streptococcus mitis, Streptococcus salivarius, Streptococcus mutans, Staphylococcus aureus, Escherichia coli, and Candida albicans. Experimental oral-rinse formulations were evaluated for inhibition-zone diameter, pH, density, and microbiological quality. Results: Polyphenols, flavonoids, tannins, alkaloids, and saponins were detected in all extracts. The aqueous extract had an IC50 of 19.3 ± 2.1 µg/mL, followed by the 60:40 hydroethanolic extract at 21.5 ± 1.8 µg/mL. Extract inhibition zones ranged from 18.1 ± 0.2 to 23.4 ± 0.4 mm. Among extract-containing formulations, inhibition zones ranged from 12.8 ± 0.3 to 18.4 ± 0.4 mm. The formulations had a mean pH of 7.28 ± 0.02 and a mean density of 1.035 ± 0.01 g/mL. The total aerobic mesophilic count was 2.2 × 10³ CFU/g and exceeded the limit applied in the study, although the specified coliforms, yeasts and moulds, Escherichia coli, and Staphylococcus aureus were not detected. Conclusion: Euphorbia thymifolia extracts demonstrated DPPH radical-scavenging and preliminary agar-diffusion activity under the conditions tested, and measurable activity remained after incorporation into experimental oral-rinse formulations. These findings support further chemical standardisation and quantitative antimicrobial investigation; however, the current results do not establish clinical efficacy, product stability, or oral safety. Optimisation of preservation and additional cytotoxicity, stability, biofilm, and in vivo studies are required.