The effect of Boswellia serrata on Giardia duodenalis

Giardia duodenalis is a parasite that colonizes the small intestine of various mammalian hosts especially in humans. The common treatment for giardiasis includes metronidazole, furazolidone and benzimidazole-based drugs which cause many side effects besides an increasing resistance problem [1,2]. Having in mind that Boswellia serrata Roxb. is used for the treatment of chronic inflammatory disorders and that this parasite is known to facilitate these conditions [3], the gum resin of this plant source was tested for antigiardial effects.

A crude extract standardized to 85% boswellic acids reduced the viability of the parasite by ca. 65% at a concentration of 20µg/mL. At the highest concentration tested (80µg/mL), the antigiardial effect was ca. 80% based on the metabolic conversion of resazurin [4]. Metronidazole (50µg/mL) served as a positive control. In search for the active principle, the extract was subjected to HPLC separation showing two major peaks at Rt 12.3 and 14.7min, respectively. The former, comprising a complex mixture of boswellic acids, exhibited pronounced antigiardial activity at 20µg/mL, as evident from a ca. 80% reduction in parasite viability. HPLC analysis showed also the presence of oleanolic acid. Preliminary analyses proved this triterpenoid only moderately active (parasite viability ca. 65% at 45µM corresponding to 20µg/mL). This finding suggested boswellic acids as the active principle. Owing to the complexity of the fractions, the isolation of distinct boswellic acid members for antigiardial activity studies is still in progress. This is the first report on antigiardial effects of boswellic acids.

Keywords: Boswellia serrata, antigiardial, boswellic acids, oleanolic acid

References: 1. Gardner B and Hill D (2001) Clin Microbiol Rev 14: 114–128

2. Upcroft P and Upcroft J (2001) Clin Microbiol Rev 14: 150–164

3. Layton MA et al. (1998) Brit J Rheumatol 37: 581–583

4. Bénéré E et al. (2007)J Microbiol Methods 71: 101–106