Caryopteris mongolica Bunge (Lamiaceae) grows in areas such as Khentii, Khangai, Mongol Daguur, Mongol Altai, and Dornod Govi in Mongolia and some areas of northern China.
C. mongolica has long been used as a traditional medicine in Mongolia to alleviate aches, oedema, and rheumatism [
1]. We have reported the phytochemical analysis of root extract of
Caryopteris mongolica. We isolated of three new compounds and five known diterpene derivatives, namely, demethylcryptojaponol, incanone, 6α-hydroxydemethylcryptojaponol, cyrtophyllone B, and 14-deoxycoleon U, from the root extract of
Caryopteris mongolica, used HPLC, MS and NMR techniques. Among these isolates, a new compound of abietane diterpene derivatives showed strong antibacterial activity [
2].
Brucella is a gram-negative, aerobic, coccobacillary, non-motile microorganism [
3]. In addition,
Brucella species are facultative intracellular pathogens that localize predominantly in the cells and organs of the mononuclear phagocytic system, such as macrophages in the liver and spleen [
4]. Brucellosis mainly affects domestic animals, in which
Brucella colonize the reticulendothelial system and genital organs, leading to abortion, stillbirth, orchitis, epididymitis, and infertility and resulting in significant economic losses. The illness continues to be one of the most widely distributed zoonoses and is transmissible to humans [
5,
6]. Human brucellosis is usually caused by
Brucella melintensis and has a wide spectrum of clinical symptoms, including irregular fever, sweating, arthralgia, myalgia, headache and weakness [
7]. The reported incidence and prevalence of the disease vary widely in nomadic livestock in Mongolia. Selenge T., and others reported that 20.2%, or one in five, herders are infected with brucellosis [
8]. The current treatment for human brucellosis requires a combination of antibiotics for long periods of time because antibiotics either lose their antimicrobial activity in the intracellular environment or do not persist long enough to produce a therapeutic effect [
9]. World Health Organization guidelines recommend a 6-week course of doxycycline plus rifampin [
10]. More recent recommendations also propose the use of doxycycline for 6 weeks with the aminoglycoside streptomycin for 2 to 3 weeks or with gentamicin for 1 week [
11]. Combination therapies are more effective than single-agent therapies; however, new therapies are necessary due to the difficulties of patient adherence to the treatment itself along with the side effects of combination therapy and the dangers of antibiotic resistance [
12]. Herbal treatments are gentle, inexpensive and effective in controlling the disease. On the basis of the in vitro screening results, the
C. mongolica root extract had high anti-
Brucella activity against
B. melintensis (a concentration of 50 μg/disc produced an inhibition zone of 15 mm). To identify the anti-
Brucella activity of the crude extract of
C. mongolica root, we used the disc diffusion method.
B. melitensis was grown in tryptone soy broth media for 72 h, and 100 μl (10
6 CFU/ml) was spread over the surface of tryptone soy agar medium in Petri dishes with diffusion discs treated with the root extract. Doxycycline-treated discs (a concentration of 10 μg/disc produced an inhibition zone of 35 mm) were used as a positive control. In other studies, plants such as
Scrophularia deserti [
13],
Origanum syriacum, Thymus syriacus [
14],
Prunus mahaleb seeds [
15],
Satureja hortensis [
16],
Oliveria decumbens [
17],
Teucrium polium [
18], and
Moringa oleifera [
19] have been examined for in vitro activity against
Brucella. However, studies have not reported the efficacy of these medicinal plants for the in vivo treatment of brucellosis. The aim of this study was to evaluate the in vivo antibacterial activity of the
C. mongolica root extract against
B. melitensis.