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DOI: 10.1055/s-0034-1394815
Diterpenes of the kaurane type: Bactericidal kinetics and synergistic effect associated with chlorhexidine
Among the diseases of the oral cavity, endodontic infections are a major concern. The microorganisms that cause such diseases are persistent, mostly as a consequence of inefficient chemical-mechanical treatment [1]. Therefore, the search for new compounds from plant sources has become an important strategy to find biologically active components that can help clinicians treat bacterial infections [2,3]. This study aimed to evaluate the bactericidal kinetics and determine the fractionated inhibitory concentration index of the most promising diterpenes isolated from the leaves of M. glomerata against bacteria that cause endodontic infections. Previous studies by our research group reported on the antibacterial activity of 12 ent-kaurane diterpenes against 14 bacteria isolated from endodontic infections. ent-Kaurenoic acid (1) and its sodium salt (2) displayed very promising MIC values (lower than 10 µg/mL) against Porphyromas gingivalis and Peptostreptococcus micros. Here, the bactericidal kinetic assays revealed that the behavior of kaurane diterpenes against the tested bacteria varied as a function of the compound concentration and microorganism sensitivity. Diterpene 1 eliminated P. micros and P. gingivalis within 12 and 72h of incubation, respectively. As for diterpene 2, its bactericidal effect became evident after 18 and 48h of incubation in the case of P. micros and P. gingivalis, respectively. With respect to synergism, combination of the diterpenes with chlorhexidine showed that the resulting interaction did not affect the action of the individual diterpene against P. gingivalis (ATCC) and P. micros (clinical isolate). Hence, diterpenes of the kaurane type are an important class of natural products and should aid the search for novel irrigating compounds with potential application in the treatment of endodontic infections.
Acknowledgements: The authors tank to FAPESP for funds and grants (process number 2012/25237 – 0).
Keywords: Kaurane, antibacterial activity, diterpene, IFIC, bactericidal kinetics
References:
[1] Basrani B. (2011) Alpha Omegan 104: 26 – 34.
[2] Carter GT. (2011) Nat Prod Rep 28: 1783 – 1789.
[3] Montanari CA, Bolzani VS. (2001) Quim Nova, 24: 105 – 111.