In-vitro antibacterial properties of clove and cinnamon and their principle chemical constituents eugenol and trans-cinnamaldehyde against aggregatibacter actinomycetemcomitans

The use of antibiotics for the cure of infectious diseases first started in 1940's when the first antibiotic was discovered. With the passing years burgeoning classes of antibiotics promised the cure of almost all the infectious diseases. However, within a few years, development of resistance against antibiotics by the microorganisms placed a new challenge for future medical advances in the treatment of infectious diseases. Only six decades later it looks like the miracle of antibiotics is over. More and more bacteria have developed resistance against more and more antibiotics. The crisis today is accentuated by the limited number of new antibiotics, less number of researches being done on the antibiotics and limited number of new compounds and new targets. The search of plant products as antimicrobial agents has been growing in the last few decades. Clove and cinnamon are the spices that are very commonly used for flavoring food and beverages. The antimicrobial properties of clove and cinnamon against different bacteria are well documented in the previous research literature. In this study we tested the in-vitro antibacterial properties of ethanolic extracts of clove and cinnamon and their principle chemical constituents, eugenol and trans-cinnamaldehyde against Aggregatibacter actinomycetemcomitans. A. actinomycetemcomitans is a gram negative, facultative, anaerobic bacterium and is associated with a variety of infectious diseases. A. actinomycetemcomitans is a major etiologic agent in localized aggressive periodontitis (LAP). Also, A. actinomycetemcomitans has been isolated from the patients with infective endocarditis, infections of urinary tract and brain. In this study, we found that ethanolic extracts of clove, cinnamon and their principle chemical constituents, eugenol and trans-cinnamaldehyde respectively exhibit excellent growth inhibitory activity against different serotypes of A. actinomycetemcomitans. Eugenol and trans-cinnamaldehyde exhibit killing times of less than 3 hours. Trans-cinnamaldehyde shows the inhibition of growth of A. actinomycetemcomitans at much lower concentrations when compared to eugenol. The results from these experiments suggest that clove and cinnamon can be useful in prevention of local and systemic infections caused by A. actinomycetemcomitans. However, further studies are needed to investigate efficacy and safety of these antibiotics when used in-vivo against A. actinomycetemcomitans.