In vitro and in vivo activities of Chios mastic gum extracts and constituents against Helicobacter pylori

Abstract

The extracts and pure major constituents of Chios mastic gum (resin of Pistacia lentiscus var. chia) were tested for their activities against Helicobacter pylori. A total mastic extract without polymer (TMEWP) was prepared after removal of the contained insoluble polymer in order to ameliorate solubility and enhance in vivo activity. Administration of TMEWP to H. pylori SS1-infected mice over the period of 3 months with an average dose of 0.75 mg/day led to an approximately 30-fold reduction in the H. pylori colonization (1.5 log CFU/g of tissue). However, no attenuation in the H. pylori-associated chronic inflammatory infiltration and the activity of chronic gastritis was observed. To further characterize potential active mastic constituents, the TMEWP was separated into an acidic and a neutral fraction. Both were extensively characterized by nuclear magnetic resonance and mass spectroscopy to elucidate the structure of the components contained within each fraction. After chromatographic separation, the acid fraction gave the major triterpenic acids, while the neutral fraction gave several triterpenic alcohols and aldehydes. Mastic extracts and isolated pure triterpenic acids were tested for in vitro activity against a panel of 11 H. pylori clinical strains. The acid fraction was found to be the most active extract (minimum bactericidal concentration [MBC], 0.139 mg/ml), and the most active pure compound was isomasticadienolic acid (MBC, 0.202 mg/ml [0.443 mM]). Our results show that administration of TMEWP may be effective in reducing H. pylori colonization and that the major triterpenic acids in the acid extract may be responsible for such an activity.

Figures

FIG. 1.

Extraction of Chios mastic gum.

FIG. 2.

Triterpenic compounds isolated from mastic acidic and neutral fractions.

FIG. 3.

H. pylori colonization in H. pylori-infected mice following continuous administration of total mastic extract without the polymer (SMH; n = 10 animals) or left untreated (SH; n = 9 animals). Viable H. pylori counts are expressed in log CFU/g gastric tissue. A moderate 1.5-log reduction in H. pylori colonization was observed (P = 0.0024) in the SMH study group compared to the SH control group.

FIG. 4.

Serum anti-H. pylori IgG antibody response in H. pylori-infected animals treated with total mastic extract without the polymer (SMH) or left untreated (SH). Uninfected control mice that received total mastic extract without the polymer are also depicted (SM). Mouse sera were diluted to 1:50. No difference in anti-H. pylori titers was observed at 12 weeks postinfection between the SMH and SH groups.

FIG. 5.

Bactericidal activity of mastic gum extracts against H. pylori in a liquid medium. H. pylori strains LAVHP-6 (more resistant strain) and LAVHP-7 (most susceptible strain) were cultured under microaerophilic conditions in BHI as described in Materials and Methods and exposed to acidic, TMEWP, and neutral fractions at the concentrations depicted in the legend. After further incubation, viability was determined at each time point.