Anticariogenic properties of a flavone present in Dodonaea viscosa var. angustifolia

Objectives: The aim of this study was to analyse the phytochemical constituents of D. viscosa var. angustifolia (DVA) and establish their beneficial effects against cariogenic bacteria S. mutans.
Methods: The crude extract from DVA leaves was fractionated into six fractions (F1-F6) using chromatography. The Minimum Inhibitory Concentrations (MIC) and Minimum Bactericidal Concentrations (MBC) were determined. The effect of the six fractions on biofilm formation and acid production were investigated. The most active fraction (F5) was further fractionated, purified, identified and elucidated using GC-MS and NMR. Cytotoxic effect of crude extract and active subfraction was studied using cell lines. Results were analyzed using Wilcoxon rank-sum test (Mann-Whitney).
Results: The MIC and MBC of the fractions and crude extract ranged from 0.39 to 12.5 mg/ml. F5 showed lowest MBC. At 0.2 mg/ml, F5 reduced biofilm formation by 93.3% and reduced acid production in S. mutans. Subfraction 5.1 showed higher antimicrobial activity compared to the crude extract and F5. Subfraction 5.1 inhibited biofilm formation at both 6 hours (94% reduction) and 24 hours (99% reduction) which was higher compared to the crude extract (87% reduction at 0.78 mg/ml after 6 hours). Subfraction 5.1 exhibited a higher inhibitory effect on acid production compared to the crude extract. Subfraction 5.1 was identified as, 5,6,8-Trihydroxy-7,4^l-dimethoxyflavone. Cytotoxicity analysis of the crude extract and subfraction 5.1 showed IC₅₀ values of 0.09 mg/ml and 0.03 mg/ml respectively
Conclusions: DVA contained an anticariogenic constituent, 5,6,8-Trihydroxy-7,4^l-dimethoxyflavone and its safety was established, therefore it has potential for use in the oral cavity to prevent dental caries