Antimicrobial Activity of Traditional Medicinal Plant Extracts against Bacterial and Fungal Strains Causing Dental Caries: An in Vitro Study

The use of plant extracts or their compounds as antimicrobial agents for oral infections worldwide represents that herbal medicines could be used as an effective alternative method in oral health care. This study aimed to evaluate the antifungal and antibacterial effects of five traditional medicinal plant extracts on standard and clinical strains of bacteria and fungi causing dental caries.

Aqueous and methanolic extracts of Zataria multiflora, Lawsonia alba, Zizyphus spina-christi, Myrtus communis, and Citrus aurantium were prepared using maceration method. The minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) of the prepared extracts were evaluated against bacterial (Streptococcus sanguinis and S. mutans) and fungal (Candida albicans, C. krusei, and C. tropicalis) isolates using broth microdilution method.  

Aqueous extracts of the studied plants showed no antimicrobial effects on the studied microorganisms, except M. communis and C. aurantium. The results indicated the antimicrobial potency of the methanolic extract of M. communis (MIC range =2 to 64 µg/mL) against all the studied microorganisms, followed by Z. multiflora (MIC range = 512-2048 µg/mL), L. alba (MIC range = 1024-2048 µg/mL), C. aurantium (MIC range = 1024-4096 µg/mL), and Z. spina-christi (MIC range=2048- ˃4096 μg/mL).  Also, the lowest MMCs against the studied strains were related to the methanolic extract of M. communis (MMC range = 16-512 µg/mL).

The results showed remarkable antimicrobial effects of M. communis extract, which could be a suitable alternative to chemical mouthwashes to prevent and control oral infections.