Antimicrobial Potential of Selected Natural Compounds: A Comparative Study on Enterococcus faecalis

The present study aimed to assess and compare the antimicrobial effectiveness of three natural plants - Neem (Azadirachta indica), Turmeric (Curcuma longa) and Guava (Psidium guajava) against one of the endodontic pathogens, that is, Enterococcus faecalis.  Broth-based assays were used to determine minimum inhibitory concentrations (MICs) by measuring optical density.

All the extracts used in the study showed antimicrobial potential, with Curcuma longa (turmeric) having the best inhibitory effect. Psidium guajava (guava), on the other hand, was relatively least active. The observed antimicrobial effects in the extracts are attributed to various bioactive compounds present in these plants. Neem leaves (Azadirachta indica) have azadirachtin, nimbin and nimbidin; turmeric rhizome has curcumin, while guava leaves are known to contain flavonoids such as quercetin and tannins.  The phytochemicals may have demonstrated antimicrobial effects against bacteria by disrupting cell wall integrity, inhibiting essential enzymes, and interfering with microbial metabolic pathways.

These findings suggest that turmeric extract has significant antibacterial potential and can serve as a natural alternative for managing endodontic infections. The article highlights the promise of plant extracts in developing new therapeutic protocols for dental procedures.

Antimicrobial activity, Endodontic pathogens, Natural compounds, Turmeric, Minimum inhibitory concentration (MIC)

Abdallah EM, Alhatlani BY, de Paula Menezes R, Martins CHG. Back to Nature: Medicinal Plants as Promising Sources for Antibacterial Drugs in the Post-Antibiotic Era. Plants (Basel). 2023;12(17):3077. doi:10.3390/plants12173077

Adamczak A, Ożarowski M, Karpiński TM. Curcumin is a natural antimicrobial agent with strain-specific activity. Pharmaceuticals (Basel). 2020;13(7):153. doi:10.3390/ph13070153.

Akkalwar D, Boriwar S, Devnani D. Review on pharmacological insights and antimicrobial potential of medicinal plants. Transform Med Mater. 2026;100002. doi:10.1016/j.trmm.2026.100002.

Alghamdi F, Shakir M (2020) The Influence of Enterococcus faecalis as a Dental Root Canal Pathogen on Endodontic Treatment: A Systematic Review. Cureus 12(3): e7257. doi:10.7759/cureus.7257

Altemimi, A., Lakhssassi, N., Baharlouei, A., Watson, D. G., & Lightfoot, D. A. (2017). Phytochemicals: Extraction, Isolation, and Identification of Bioactive Compounds from Plant Extracts. Plants (Basel, Switzerland), 6(4), 42. https://doi.org/10.3390/plants6040042

Anwar MA, Sayed GA, Hal DM, et al. Herbal remedies for oral and dental health: a comprehensive review of their multifaceted mechanisms including antimicrobial, anti-inflammatory, and antioxidant pathways. Inflammopharmacology. 2025;33(3):1085-1160. doi:10.1007/s10787-024-01631-8

Azwanida, N.N. (2015) A Review on the Extraction Methods Use in Medicinal Plants, Principle, Strength and Limitation. Medicinal and Aromatic Plants, 4, 3. https://doi.org/10.4172/2167-0412.1000196.

Biswas, B., Rogers, K., McLaughlin, F., Daniels, D., & Yadav, A. (2013). Antimicrobial Activities of Leaf Extracts of Guava (Psidium guajava L.) on Two Gram-Negative and Gram-Positive Bacteria. International journal of microbiology, 2013, 746165. https://doi.org/10.1155/2013/746165.

Chaitanya BV, Somisetty KV, Diwan A, Pasha S, Shetty N, Reddy Y, et al. Comparison of antibacterial efficacy of turmeric extract on Enterococcus faecalis: an in vitro study. J Clin Diagn Res. 2016;10(10):ZC55–7. doi:10.7860/JCDR/2016/19718.8650.

Gogineni S, Ganipineni K, Babburi S, et al. Evaluation of Vinegar as a Disinfectant for Extracted Human Teeth - An in-Vitro Study. J Clin Diagn Res. 2016;10(7):ZC50-ZC52. doi:10.7860/JCDR/2016/19025.8167

Gutierrez-Montiel D, Guerrero-Barrera AL, Moreno-Flores AC, Ramírez-Castillo FY, Chávez-Vela NA, Martínez-Ávila GCG, et al. Antimicrobial and antibiofilm effects of guava leaf extracts against Enterococcus faecalis and Staphylococcus epidermidis. Front Antibiot. 2025;4:1615787. doi:10.3389/frabi. 2025.1615787.

Halkai RS, Hegde MN, Halkai KR. Evaluation of Enterococcus faecalis adhesion, penetration, and method to prevent the penetration of Enterococcus faecalis into root cementum: Confocal laser scanning microscope and scanning electron microscope analysis. J Conserv Dent. 2016;19(6):541-548. doi:10.4103/0972-0707.194025

Hussain Y, Alam W, Ullah H, et al. Antimicrobial Potential of Curcumin: Therapeutic Potential and Challenges to Clinical Applications. Antibiotics (Basel). 2022;11(3):322. doi:10.3390/antibiotics11030322

Huynh HD, Nargotra P, Wang HD, Shieh CJ, Liu YC, Kuo CH. Bioactive Compounds from Guava Leaves (Psidium guajava L.): Characterization, Biological Activity, Synergistic Effects, and Technological Applications. Molecules. 2025;30(6):1278. doi:10.3390/molecules30061278

Jain OP, Lairenlakpam R, Priya P, Chouhan V, Anand K, Dhandoria D. A Comparative Evaluation of Antimicrobial Efficacy of Five Different Herbal Solutions: Propolis, Azadirachta Indica (Neem), Triphala, Green Tea, and Turmeric against Enterococcus Faecalis and Debris Removal from the Root Canal Using Two Irrigation Protocols-Manual and Ultrasonic-An Ex Vivo Study. J Pharm Bioallied Sci. 2024;16(Suppl 4):S3834-S3836. doi:10.4103/jpbs.jpbs_1316_24.

Joy Sinha D, D S Nandha K, Jaiswal N, Vasudeva A, Prabha Tyagi S, Pratap Singh U. Antibacterial Effect of Azadirachta indica (Neem) or Curcuma longa (Turmeric) against Enterococcus faecalis Compared with That of 5% Sodium Hypochlorite or 2% Chlorhexidine in vitro. Bull Tokyo Dent Coll. 2017;58(2):103-109. doi:10.2209/tdcpublication.2015-0029.

Matei AT, Visan AI. Mechanism, Efficacy, and Safety of Natural Antibiotics. Antibiotics (Basel). 2025;14(10):981. doi:10.3390/antibiotics1410098

Matsuoka M, Soria SA, Pires JR, Sant'Ana ACP, Freire M. Natural and induced immune responses in oral cavity and saliva. BMC Immunol. 2025;26(1):34. doi:10.1186/s12865-025-00713-8

Megha S, Venkatesha D. Comparative study to determine antimicrobial property of neem leaves (Azadirachta indica) extracts using various solvents obtained from two geographical areas. J Med Sci Health. 2023;9(1):57–63.

Mungwari CP, King'ondu CK, Sigauke P, Obadele BA. Conventional and modern techniques for bioactive compounds recovery from plants: Review. Sci Afr. 2025;27:e02509. doi:10.1016/j.sciaf.2024.e02509.

Nawrocka A, Łukomska-Szymańska M. Extracted human teeth and their utility in dental research. Recommendations on proper preservation: A literature review. Dent Med Probl. 2019;56(2):185-190. doi:10.17219/dmp/105252

Neelakantan P, Subbarao C, Sharma S, Subbarao CV, Garcia-Godoy F, Gutmann JL. Effectiveness of curcumin against Enterococcus faecalis biofilm. Acta Odontol Scand. 2013;71(6):1453–7. doi:10.3109/00016357.2013.769627.

Odo EO, Ikwuegbu JA, Obeagu EI, Chibueze SA, Ochiaka RE. Analysis of the antibacterial effects of turmeric on particular bacteria. Medicine (Baltimore). 2023;102(48):e36492. doi:10.1097/MD.0000000000036492.

Pereira GA, Chaves DSA, Silva TME, et al. Antimicrobial Activity of Psidium guajava Aqueous Extract against Sensitive and Resistant Bacterial Strains. Microorganisms. 2023;11(7):1784. doi:10.3390/microorganisms11071784

Sasidharan S, Chen Y, Saravanan D, Sundram KM, Yoga Latha L. Extraction, isolation and characterization of bioactive compounds from plants' extracts. Afr J Tradit Complement Altern Med. 2011;8(1):1-10.

Singh A, Tripathi P, Srivastava A, Ali SM, Rekhi L. Antibacterial activity of six indigenous Indian plants: Acacia nilotica (Fabaceae), Albizia saman (Fabaceae), Azadirachta indica (Meliaceae), Carica papaya (Caricaceae), Cymbopogon citratus (Poaceae) and Mangifera indica (Anacardiaceae). Afr J Biotechnol. 2016;15(16):666-669. doi:10.5897/AJB2015.14834

Stuart CH, Schwartz SA, Beeson TJ, Owatz CB. Enterococcus faecalis: its role in root canal treatment failure and current concepts in retreatment. J Endod. 2006;32(2):93-98. doi:10.1016/j.joen.2005.10.049.

Surana A, Priya C, Bhavya A, Suparna GS, Rolly SA, Kewlani M. Comparative evaluation of minimal inhibitory concentration and minimal bactericidal concentration of various herbal irrigants against Enterococcus faecalis. J Conserv Dent Endod. 2024;27(7):780–4. doi:10.4103/JCDE.JCDE_349_23.

Tripathi P, Shariq IM, Singh A. Total antioxidant potential of indigenous Indian plants. J Chem Pharm Res. 2016;8(5):579-583.

Tripathi P, Srivastava A, Rekhi L, Singh A. Screening of some edible plants for antioxidant potential. Int J Res Ayurveda Pharm. 2017;8(Suppl 2):256-261. doi:10.7897/2277-4343.082123.

Trivedi M, Singh A, Sethi P, Singh S, Jha CS, Firoz N, et al. Effect of certain medicinal plants on bacterial flora of human oral cavity. Med Plants. 2013;5(3):168-170. doi:10.5958/J.0975-6892.5.3.027

Umapathy VR, Swamikannu B, Jones S, Kiran M, Lell T, Mayasa V, et al. Effects of turmeric (Curcuma longa) on oral health. Bioinformation. 2022;18(6):538–42. doi:10.6026/97320630018538.

Vaou N, Stavropoulou E, Voidarou CC, et al. Interactions between Medical Plant-Derived Bioactive Compounds: Focus on Antimicrobial Combination Effects. Antibiotics (Basel). 2022;11(8):1014. doi:10.3390/antibiotics11081014

Wiegand I, Hilpert K, Hancock REW. Agar and broth dilution methods to determine the minimal inhibitory concentration (MIC) of antimicrobial substances. Nat Protoc. 2008;3(2):163–75.

Wylie MR, Merrell DS. The Antimicrobial Potential of the Neem Tree Azadirachta indica. Front Pharmacol. 2022;13:891535. doi:10.3389/fphar.2022.891535