Xanthorrhizol: A Potential Antibacterial Agent from Curcuma xanthorrhiza against Streptococcus mutans

Curcuma xanthorrhiza Roxb., commonly known as temu lawak or Javanese turmeric, has been traditionally used in Indonesia for food an medicinal purposes [1]. It has been reported that Curcuma xanthorrhiza confers a variety of biological activities such as antitumor [2], hypotriglyceridaemic [3], anti-inflammatory [4], antibacterial [5], etc. In this research we found that xanthorrhizol (1,3,5,10-bisabolatetraen-3-ol), isolated from Curcuma xanthorrhiza, possessed remarkable anticariogenic activity against Streptococcus mutans.

The dried rhizomes of Curcuma xanthorrhiza were purchased at the market of Yokjakarta in Indonesia (Voucher specimen No. YS98015). The rhizomes (100g) were ground and extracted with 75 % MeOH (v/v; 400ml), and further fractionations were carried out consecutively with ethyl acetate (4.8g), n-butanol (1.7g) and water (1.1g). Xanthorrhizol (0.2g) was isolated from the ethyl acetate fraction by using a silica gel column chromatography (Merck; 70–230 mesh; 5 × 43 cm; n-hexane/ethyl acetate, 10 : 1). Xanthorrhizol ([Fig. 1]) was identified by direct comparison of the ¹H-NMR, ¹³C-NMR and EI-mass spectral results with the published data [2] [6]. The specific rotation of xanthorrhizol was determined as [α]²⁰ _D: –50.2° (c = 0.65, CHCl₃).

Fig. 1 Structure of xanthorrhizol.

Antibacterial activity of xanthorrhizol was investigated by the MIC (minimum inhibitory concentration) test and the viable cell count method. MIC of xanthorrhizol against S.mutans was determined to be 2 µg/ml, which was much lower than other natural anticariogenic agents such as 16 µg/ml of sanguinarine, 125 µg/ml of tea polyphenol, 125 µg/ml of carvacrol, 250 µg/ml of isoeugenol, 500 µg/ml of eucalyptol and 500 µg/ml of thymol. Fig. [2] shows that 5 µg/ml treatment of xanthorrhizol killed completely S.mutans in a minute. This bactericidal activity is of practical significance, since applications of xanthorrhizol in mouthwash or toothpaste should be effective within a few minutes. These results suggested that xanthorrhizol could be employed as a potential anticariogenic agent.

Fig. 2 Bactericidal activity of xanthorrhizol against S.mutans (No = 10⁵cfu/ml). ♦: control, █: 1 µg/ml, ▴: 3 µg/ml, ×: 5 µg/ml.

Information in detail on the work-up procedure and copies of the original spectra are obtainable from the author of correspondence.

References

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