Isopanduratin a from Kaempferia pandurata as an active antibacterial agent against cariogenic Streptococcus mutans

An antibacterial compound active against Streptococcus mutans was isolated from Kaempferia pandurata and identified as isopanduratin A using ¹H NMR, ¹³C NMR and EI-MS. The minimum inhibitory concentration (MIC) of isopanduratin A was 4mg/l which was much lower than that of some other natural anticariogenic agents such as sanguinarine (12mg/l), green tea extract and carvacrol (125mg/l), thymol (250mg/l) and isoeugenol and eucalyptol (500mg/l). The bactericidal test showed that isopanduratin A completely inactivated S. mutans at 20mg/l in 1min. Significant inhibitory activity of isopanduratin A was also observed against S. sobrinus, S. sanguinis and S. salivarius with an MIC of 4mg/l. Damage to the cell membrane and cell wall of S. mutans by isopanduratin A was shown using transmission electron microscopy (TEM). These results suggest that isopanduratin A could be employed as a potential antibacterial agent for preventing dental caries.