In vitro comparison of antioxidant, cytotoxic, and antibacterial (against Aggregatibacter actinomycetemcomitans) effects of Citrus reticulata, Olea europaea extracts, and essential oils.

Abstract

Background: This study compared the antioxidant, cytotoxic, and antibacterial effects of Citrus reticulata (C. reticulata) peel and Olea europaea (O. europaea) leaf hydroalcoholic extracts and essential oils.

Materials and methods: In this in vitro study, the antibacterial effect of the C. reticulata and O. europaea extracts and essential oils was evaluated on Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) by the agar diffusion test. Their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by the broth microdilution method. Their cytotoxicity against human gingival fibroblasts was evaluated by the methyl thiazolyl tetrazolium assay in 24 and 72 h, and their antioxidant effect was assessed by the 2,2-diphenyl-1-picrylhydrazyl assay. Data were analyzed by ANOVA and Tukey's test (P < 0.05).

Results: The O. europaea hydroalcoholic extract and C. reticulata essential oils had significant antibacterial effects on A. actinomycetemcomitans. The highest and lowest growth inhibition zones belonged to C. reticulata essential oils (40.0 ± 0.0 mm) and O. europaea extract (32.3 ± 2.2 mm), respectively. The MIC and MBC were 0.78 v/v% for O. europaea extract and 6.25% for C. reticulata essential oils. Unlike the essential oils (1%, 5%, and 10% v/v), none of the extracts showed significant cytotoxicity at low concentrations (1% v/v). All essential oils and extracts, particularly O. europaea and C. reticulata extracts, had significant antioxidant effects.

Conclusion: Of the tested materials, O. europaea extract had the highest potential for possible use as an organic mouthwash due to its strong antibacterial and antioxidant effects and absence of cytotoxicity in low concentrations.