A Comparison of Antibacterial Effects of Licorice Root Ethanolic Extract, Chlorhexidine, and Doxycycline on Fusobacterium nucleatum: An in Vitro Study

  • Mohammadreza Tabatabaeian dentistry student, Azad university of lsfahan, isfahan, iran
  • Vahid Esfahanian* Associate professor, Department of Periodontology, Faculty of dentistry, Isfahan(khorasgan) Branch, Islamic Azad university, Isfahan, Iran (corresponding author) https://orcid.org/0000-0002-6013-8832
  • Arezoo Tahmourespour
Keywords: Antibacterial agents, Fusobacterium nucleatum, Glycyrrhiza glabra extract


Background and Aim: Antibiotics and mouthwashes which are used to prevent and treat periodontal diseases have side effects such as antibiotic resistance, mouth burning, and xerostomia. With the advancement of technology, plants have been considered as alternative antibacterial agents. Licorice plant with different species has been used in traditional medicine to treat gastritis and respiratory diseases. Considering the properties of licorice in traditional medicine, this study aimed to investigate the antibacterial properties of licorice root extract with different concentrations compared with Chlorhexidine mouthwash and Doxycycline antibiotic on Fusobacterium nucleatum in vitro. Materials and Methods: After the preparation of 0.5 McFarland bacterial suspension, the plant and its ethanolic extract, and six extract dilutions were also prepared. Agar disk diffusion and broth microdilution tests were carried out against Fusobacterium nucleatum ATCC 2558. The antibacterial effect of Chlorhexidine mouthwash 0.2% and Doxycycline 100 mg antibiotic were also determined to be compared with licorice extract. The data were analyzed using Mann-Whitney and Kruskal-Wallis statistical tests in spss26 software at a significance level of 5%. Results: All the six concentrations had significant antibacterial effects compared with each other, chlorhexidine and doxycycline (P-value<0.05). The inhibitory concentrations of extract, MIC50, MIC70, and, MIC90 were related to 12/5, 50, and 200 mg/ml, respectively. The inhibitory percentages of chlorhexidine and doxycycline were 67.6% and 88.7%, respectively. Conclusion: Licorice ethanolic extract exhibited an excellent antimicrobial effect (MIC=6.25mg/ml), so that in concentrations higher than 25, a greater antimicrobial effect was observed than in chlorhexidine (P<0.05).


Chitsazi M, Shirmohammadi A BE. Effects of herbal mouthwash on periodontal indexes: comparable persica, Matrica, chlorhexidine. J Dent Shiraz Univ Med Sci. 2007;8(4 (17)):54–60.

Farhad SZ, Aminzadeh A, Mafi M, Barekatain M, Naghney M, Ghafari MR. The effect of adjunctive low-dose doxycycline and licorice therapy on gingival crevicular fluid matrix metalloproteinase-8 levels in chronic periodontitis. Dent Res J (Isfahan). 2013;10(5):624–9.

Kanwar I, Sah AK, Suresh PK. Biofilm-mediated Antibiotic-resistant Oral Bacterial Infections: Mechanism and Combat Strategies. Curr Pharm Des. 2017;23(14):2084–95.

Dewake N, Ma X, Sato K, Nakatsu S, Yoshimura K, Eshita Y, et al. β-Glycyrrhetinic acid inhibits the bacterial growth and biofilm formation by supragingival plaque commensals. Microbiol Immunol. 2021;65(9):343–51.

Carranza F, Newman M. G, Takei H KD. Carranza’s clinical periodontology.11 th ed.St Louis:Elsevier,2012:(12-26) (58-80) (84-103) (129-131) (281-282).

Rezaie E, Bayani M, Arjomandzadegan M. The Inhibitory and Antibacterial Effects of Peppermint Essential Oil on Periodontal Photogenes. J Arak Univ Med Sci. 2020;23(2):172–83.

Mahmudpourmoteshakker T, Rafiee E, Farhad S AA. Comparison of the Effect of Doxycycline and Licorice on Chronic Periodontitis – A Clinical Trial Study. J Res Dent Sci. 2014;11(3):123–9.

Tanabe S, Desjardins J, Bergeron C, Gafner S, Villinski JR, Grenier D. Reduction of bacterial volatile sulfur compound production by licoricidin and licorisoflavan A from licorice. J Breath Res. 2012;6(1):16006.

La VD, Tanabe S, Bergeron C, Gafner S, Grenier D. Modulation of matrix metalloproteinase and cytokine production by licorice isolates licoricidin and licorisoflavan A: potential therapeutic approach for periodontitis. J Periodontol. 2011;82(1):122–8. Available from: https://pubmed.ncbi.nlm.nih.gov/20722535.

Lang NP, Berglundh T, Giannobile WV, Sanz M E. Lindhe’s Clinical Periodontology and Implant Dentistry, 2 Volume Set. John Wiley & Sons; 2021 Oct 18.

Khoshnam S E, Farzaneh M, valipour M, Bahaoddini A valipour A. Review of the phytochemical, pharmacological and physiological properties of Licorice (Glycyrrhizaglabra). Vol. 4, Clinical-Excellence. 2015. p. 56–71.

Mamedov NA, Egamberdieva D. Phytochemical Constituents and Pharmacological Effects of Licorice: A Review. In: Ozturk M, Hakeem KR, editors. Plant and Human Health, Volume 3: Pharmacology and Therapeutic Uses. Cham: Springer International Publishing; 2019. p. 1–21.

Hasan MK, Ara I, Mondal MSA, Kabir Y. Phytochemistry, pharmacological activity, and potential health benefits of Gly cyrrhiza glabra. Heliyon. 2021;7(6):e07240.

Azmoudeh F, Aslanimehr M, Lourizadeh N. Effect of Glycyrrhiza glabra extract on Streptococcus mutans and Candida albicans (in vitro study). URMIAMJ. 2017;28(6):394–400.

Khanahmadi M M, Naghdi Badi H, Akhondzadeh S, Khalighi Sigaroodi F, Mehrafarin A SS et al . A Review on Medicinal Plant of Glycyrrhiza glabra L. J Med Plants. 2013;12(46):1–12.

El-Saber Batiha G, Magdy Beshbishy A, El-Mleeh A, Abdel-Daim MM, Prasad Devkota H. Traditional Uses, Bioactive Chemical Constituents, and Pharmacological and Toxicological Activities of Glycyrrhiza glabra L. (Fabaceae). Biomolecules. 2020;10(3).

Jiang M, Zhao S, Yang S, Lin X, He X, Wei X, et al. An “essential herbal medicine”-licorice: A review of phytochemicals and its effects in combination preparations. J Ethnopharmacol. 2020;249:112439.

Jain P, Sontakke P, Walia S, Yadav P, Biswas G, Kaur D. Assessment of the efficacy of licorice versus 0.2% chlorhexidine oral rinse on plaque-induced gingivitis: A randomized clinical trial. Indian J Oral Heal Res. 2017;3(1):15–8.

Sidhu P, Shankargouda S, Rath A, Hesarghatta Ramamurthy P, Fernandes B, Kumar Singh A. Therapeutic benefits of liquorice in dentistry. J Ayurveda Integr Med. 2020;11(1):82–8.

Youngseok H, Tae-Jong K. Conditions for Preparing Glycyrrhiza uralensis Extract for Inhibiting Biofilm Formation of Streptococcus mutans. 2019 Mar 25;47(2):178–88. Available from: https://doi.org/10.5658/WOOD.2019.47.2.178

Malvania EA, Sharma AS, Sheth SA, Rathod S, Chovatia NR, Kachwala MS. In Vitro Analysis of Licorice (Glycyrrhiza glabra) Root Extract Activity on Streptococcus mutans in Comparison to Chlorhexidine and Fluoride Mouthwash. J Contemp Dent Pract. 2019;20(12):1389–94.

Haraszthy VI, Zambon JJ, Trevisan M, Zeid M GR. Identification of periodontal pathogens in atheromatous plaques. 2000;71(10):1554-60. J Periodontol. 71(10):1554–60.

Gunsolley JC. Clinical efficacy of antimicrobial mouthrinses. Journal of dentistry. 2010;38:S6-10. A

Fabricant DS, Farnsworth NR. The value of plants used in traditional medicine for drug discovery. Environmental health perspectives. 2001;109(suppl 1):69-75.

Burt S. Essential oils: their antibacterial properties and potential applications in foods—a review. International journal of food microbiology. 2004;94(3):223-53.

Ajagannanavar SL, Battur H, Shamarao S, Sivakumar V, Patil PU, Shanavas P. Effect of aqueous and alcoholic licorice (glycyrrhiza glabra) root extract against streptococcus mutans and lactobacillus acidophilus in comparison to chlorhexidine: an in vitro study. J Int oral Heal JIOH. 2014;6(4):29–34.

Marcoux E, Lagha A Ben, Gauthier P, Grenier D. Antimicrobial activities of natural plant compounds against endodontic pathogens and biocompatibility with human gingival fibroblasts. Arch Oral Biol. 2020;116:104734.

Original Article