Traditional Medicinal Plant Extracts and Natural Products with Activity against Oral Bacteria: Potential Application in the Prevention and Treatment of Oral Diseases

Abstract

Oral diseases are major health problems with dental caries and periodontal diseases among the most important preventable global infectious diseases. Oral health influences the general quality of life and poor oral health is linked to chronic conditions and systemic diseases. The association between oral diseases and the oral microbiota is well established. Of the more than 750 species of bacteria that inhabit the oral cavity, a number are implicated in oral diseases. The development of dental caries involves acidogenic and aciduric Gram-positive bacteria (mutans streptococci, lactobacilli and actinomycetes). Periodontal diseases have been linked to anaerobic Gram-negative bacteria (Porphyromonas gingivalis, Actinobacillus, Prevotella and Fusobacterium). Given the incidence of oral disease, increased resistance by bacteria to antibiotics, adverse affects of some antibacterial agents currently used in dentistry and financial considerations in developing countries, there is a need for alternative prevention and treatment options that are safe, effective and economical. While several agents are commercially available, these chemicals can alter oral microbiota and have undesirable side-effects such as vomiting, diarrhea and tooth staining. Hence, the search for alternative products continues and natural phytochemicals isolated from plants used as traditional medicines are considered as good alternatives. In this review, plant extracts or phytochemicals that inhibit the growth of oral pathogens, reduce the development of biofilms and dental plaque, influence the adhesion of bacteria to surfaces and reduce the symptoms of oral diseases will be discussed further. Clinical studies that have investigated the safety and efficacy of such plant-derived medicines will also be described.

Figure 1

The development of tooth decay. (a) Initial adhesin-mediated attachment of mutans streptococci; (b) aggregation mediated by synthesis of extracellular polysaccharide; (c) metabolism of carbohydrates results in acid production, leading to demineralization and cavitation of the tooth. Plant extracts and phytochemicals have been demonstrated to inhibit any or all of these stages. That is, cidal activity against cariogenic bacteria, inhibition of adherence/aggregation/biofilm formation and inhibition of glycolytic acid production.

Figure 2

Potential application of plant extracts (a) and phytochemicals (b) in the prevention and treatment of oral diseases caused by cariogenic and periodontal microbial pathogens. Where known, the likely uses of extracts and phytochemicals are indicated with respect to their target pathogens (solid arrows) and biological activities (dashed arrows).