Antibacterial constituents from the roots of Caryopteris mongolica Bge.

In the course of our study on in vitro screening of Mongolian plants, the roots of Caryopteris mongolica have showed strong activity against Gram-positive bacteria. A literature search revealed also that a few reports on chemical composition of this plant [1,2]. Therefore, we have continued to isolate antibacterial constituents from the roost of C. mongolica.

C. mongolica Bge. (Verbenaceae) has long been used as a traditional medicine to stop bleeding after giving a birth, to contract uterus, and to treat a fever in Mongolia [3]. Chloroform extract of the roots of C. mongolica was passed through a column of silica gel. The bioactive fraction was further purified using both an ODS column and HPLC, led to the isolation of the three new compounds (1 – 3, Figure) and five known abietane diterpene derivatives, namely, demethylcryptojaponol (4), incanone (5), 6α-hydroxydemethylcryptojaponol (6), cyrtophyllone B (7) and 14-deoxycoleon U (8). These known compounds were isolated for the first time from the titled plant. The structures of the new compounds were established on the basis of spectroscopic methods. In addition, the isolates were evaluated for their antibacterial activity. Of them, a new compound 2 showed strong activity against Gram-positive bacteria, Staphylococcus aureus, S. epidermidis, Enterococcus faecalus and Micrococcus luteus. For example, inhibition zones of a new compound 2 and kanamycin, a positive control, were 27.9 and 24.8 mm, respectively, at the same dose of 25 µg/disc against M. luteus.

Fig. 1

Acknowledgements: The authors are grateful to the Science and Technology Foundation of Mongolia for partial financial support.

References:

[1] Yong-Hong Zhang et al. (2000) Pharmazie 55(11): 845 – 847.

[2] Sebastien Hannedouche et al. (1999) Phytochemistry 51:767 – 769.

[3] Ligaa U et al. (2006) Medicinal Plants of Mongolia used in Western and Eastern Medicine. JKC printing, Ulaanbaatar, Mongolia.