Anti-caries Effect Of Arnebia Euchroma (Royle) Johnst. Root Extract On Bacterial And Animal Experimental Study

Objective:The aim of this study was to assess the anti-caries effect of Arnebia euchroma（Royle）Johnst.root（AR）extract through experiments with bacteria and animal.Methods:（1）The effect of the extractive from the AR on Streptococcus mutans（S.mutans）was verified by in vitro bacteriostatic experiments.The minimal inhibit concentration(MIC₅₀)of AR extract against S.mutans planktonic cultures was determined by broth microdilution.The minimum bactericidal concentration（MBC）of AR extract against S.mutans was determined by the streak-plating method.The minimum biofilm inhibition concentration(MBIC₅₀)and minimum biofilm reduction concentration(MBRC₅₀)of S.mutans were determined by microtiter plate assay.The live/dead bacterial staining were conducted to monitor bacterial growth state in biofilm form to observe the effective of the AR extract.The adhesion amount of S.mutans labeled with fluorescent to saliva-coated hydroxyapatite was measured to determine the effect of the MBIC₅₀ and four concentrations gradients sub-MBIC₅₀ of the AR extract on the adhesion of S.mutans.（2）The anti-caries effect of the AR extract was verified by in vivo Animal experimentation.The S.mutans count in the saliva of rats was counted by plate dilution method.X-ray film and Keyes score reflected the severity of dental caries in rats.The voids and gaps in demineralized enamel was detected by CLSM.The above methods comprehensively evaluate the effectiveness of AR extract in preventing caries in vivo.The weight gain,HE staining of oral mucosa and organ coefficients of rats during the test were recorded to comprehensively evaluate the safety of the anti-caries effect of AR extract.Results:The MIC₅₀ of AR extract against S.mutans planktonic cultures and the MBC are 1mg/m L and 8mg/m L respectively.The MBIC₅₀ and the MBRC₅₀ of the AR extract to the S.mutans biofilm are 4 mg/m L and 8mg/m L respectively,8mg/m L and 4mg/m L can affect the ratio of dead bacteria in biofilm（P<0.05）,2mg/m L can affect biofilm structure.The adhesion inhibition ability of AR extract on S.mutans is in direct proportion to the drug concentration,the three concentrations of 4 mg/m L and below showed adhesion inhibition（P<0.001）,and the adhesion rate at 1 mg/m L concentration is 50%.1mg/m L and 2mg/m L AR extract can reduce the amount of S.mutans in saliva of rats,0.5mg/m L AR extract can reduce the slightly dentinal caries scores and 1mg/m L and 2mg/m L AR extract can reduce moderate dentinal caries scores and extensive dentinal caries scores,reduce the severity of caries.AR extract has no systemic toxic and side effects in vivo.Conclusion:The extract of AR can effectively inhibit the growth and adhesion of the main cariogenic bacteria and their biofilms in vitro;In vivo,it can inhibit the formation and development of rat dental caries,and prevent and cure rat dental caries safely and effectively.