Antimicrobial activity of the essential oils and non-polar extracts from leaves and flowers of Tithonia diversifolia against cariogenic bacteria

Bacteria of the Streptococcus and Lactobacillus genera, such as S. salivarius, S. mutans, S. mitis, S. sobrinus, S. sanguinis, S. salivarus and L. casei are the main microorganisms responsible for human dental caries. As part of our ongoing project on the prospection of natural products with anti-cariogenic potential, we have investigated in this work the antibacterial activity of Tithonia diversifolia (Hemsl.) A. Gray (Asteraceae), which is used in the Brazilian medicine folk as anti-inflammatory [1]. The minimum inhibition concentration (MIC) values of the essential oils of flowers (EOf) and leaves (EOl), and their respective n-hexane extracts were determined by using the broth microdilution method. The n-hexane extracts of leaves and flowers, and the EOl were inactive against the panel of selected bacteria, having displayed MIC values between 1000 to 2000µg/mL, whereas the EOf exhibited moderate activity (MIC=250µg/mL) against S. mitis, S. sanguinis, S. sobrinus and L. casei. The lowest MIC value was obtained for the EOl against S. mutans (MIC=125µg/mL). β-caryophyllene (11.04%) was found to be the major constituent in the EOl, however it has been reported to exhibit weak activity (MIC=500µg/mL). Further studies to verify the occurrence of possible synergistic effects between β-caryophyllene and other minor constituents in the EOl are in progress.

Acknowledgement: FAPESP (Proc. 2009/09491–1), CAPES, CNPq.

References: [1] Owoyele VB et al. (2004)J Ethnopharmacol 90: 317–321.