Abstract
Plants produce a number of antimicrobial substances and the roots of the shrub Salvadora persica have been demonstrated to possess antimicrobial activity. Sticks from the roots of S. persica, Miswak sticks, have been used for centuries as a traditional method of cleaning teeth. Diverging reports on the chemical nature and antimicrobial repertoire of the chewing sticks from S. persica led us to explore its antibacterial properties against a panel of pathogenic or commensal bacteria and to identify the antibacterial component/s by methodical chemical characterization. S. persica root essential oil was prepared by steam distillation and solid-phase microextraction was used to sample volatiles released from fresh root. The active compound was identified by gas chromatography-mass spectrometry and antibacterial assays. The antibacterial compound was isolated using medium-pressure liquid chromatography. Transmission electron microscopy was used to visualize the effect on bacterial cells. The main antibacterial component of both S. persica root extracts and volatiles was benzyl isothiocyanate. Root extracts as well as commercial synthetic benzyl isothiocyanate exhibited rapid and strong bactericidal effect against oral pathogens involved in periodontal disease as well as against other Gram-negative bacteria, while Gram-positive bacteria mainly displayed growth inhibition or remained unaffected. The short exposure needed to obtain bactericidal effect implies that the chewing sticks and the essential oil may have a specific role in treatment of periodontal disease in reducing Gram-negative periodontal pathogens. Our results indicate the need for further investigation into the mechanism of the specific killing of Gram-negative bacteria by S. persica root stick extracts and its active component benzyl isothiocyanate.
Highlights
Periodontitis is a complex disease in which inflammatory responses due to bacteria and host interactions play a major role in expression and progression of the disease [1]
Assessment of antibacterial properties of S. persica essential oil To assess the antibacterial properties of the essential oil the following bacteria were used; the oral pathogens A. actinomycetemcomitans, P. gingivalis, S. mutans and L. acidophilus, the intestinal pathogen S. typhimurium, the environmentally acquired pathogen P. aeruginosa, and the opportunistic pathogens S. aureus, S. pyogenes, H. influenzae as well as the commensals E. coli, E. faecalis, E. faecium, L. fermentum
Our finding that extracts of chewing sticks, Miswak, from the Salvadora persica root target Gram-negative bacteria indicates that these chewing sticks may be useful in maintaining or restoring a microflora associated with periodontal health and stability
Summary
Periodontitis is a complex disease in which inflammatory responses due to bacteria and host interactions play a major role in expression and progression of the disease [1]. Gram-negative bacteria such as Tannerella forsythia (Bacteroides forsythus), Porphyromonas gingivalis, and Treponema denticola are found in significantly higher levels in patients with chronic and aggressive periodontitis and often called the red complex bacteria [3,4,5] These Gram-negative bacteria, along with Aggregibacter (Actinobacillus) actinomycetemcomitans, colonize the gingival pockets; they are strong inducers of inflammation and tissue destruction and with a highly developed capability to evade host immune responses and resist antimicrobial treatment [6,7,8,9,10,11]. In addition to the mechanical removal of dental plaque and stimulation of the gingival tissues, there were early reports indicating that the root of S. persica exerts antimicrobial activity [13,14,15] These studies diverge in methods used for root preparation or extraction. More recently we could establish that cut chewing stick pieces from the root of S. persica that were suspended by a thread above the surface of a bacterial lawn exhibited strong bacterial killing capacity [21]
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