Effect of Swedish Bitters on Selected Rat Cytochrome P450 Enzyme Activity and Hepatic Antioxidant Levels

Abstract

Background: The use of herbal products has gained popularity especially in developing countries. A number of patients are known to take these herbal products concurrently with conventional drugs. Concomitant use of herbal preparations and conventional drugs may result in herb-drug interactions, often via modulation of drug metabolizing enzymes, in particular, Cytochrome P450 (CYP) enzymes. Swedish bitters is one of such herbal preparations on the market which may be concomitantly administered with other conventional drugs because of its use as a digestif. Aims: The aims of the current study were to determine the effect of Swedish bitters on the activities of rat liver microsomal CYP1A2, CYP3A4, CYP2B6, CYP2C9 and CYP2D6 enzymes, and also its effect on hepatic antioxidant levels. The effect of Swedish bitters on rat hematological and biochemical parameters was also assessed. Methods: Male Sprague-Dawley rats 6-8 weeks old were put into 5 groups (5 rats/group). The groups consisted of a positive control (15 mg/kg/day of phenobarbital), a negative control (distilled water), and low (5 mL/kg/day), medium (10 mL/kg/day) and high (20 mL/kg/day) doses of Swedish bitters, respectively. After a 7-day administration period of the aforementioned treatments, the rats were euthanized and blood obtained by cardiac puncture. The livers were isolated, immediately placed on ice and stored at -80oC until use. Microsomal preparations were obtained from harvested livers by homogenization and differential centrifugation. The substrates of each specific CYP was added to microsomal preparations in phosphate buffer (pH 7.4) at 37oC and their metabolites measured using spectrophotometric and chromatographic assays. Effect of Swedish bitters on enzyme activity was determined based on metabolite levels. Antioxidant levels/reactions such as Glutathione (GSH), Lipid peroxidation (LPO), Superoxide Dismutase (SOD) and Catalase (CAT) were evaluated in liver cytosol using standard methods. Additionally, hematological and biochemical parameters in the various groups from blood collected were determined using automated analyzers. Results: Results showed that Swedish bitters increased the activities of CYP2B1/2B2, CYP3A4, CYP2C9 and CYP2D6; with CYP2C9 significantly increased (p < 0.01). The activity of CYP1A1/1A2 did not differ significantly compared to the non-treated groups. There was a marginal increase in CYP1A2 activity in treatment groups, however, this was not statistically significant. Furthermore, with antioxidant levels/reactions assayed in liver cytosol, there was a dose dependent decrease in GSH levels and increase in SOD activity, however, both were not statistically significant. Catalase activity was found to have decreased dose-dependently, with the rats that received high dose of Swedish bitters showing a significant decrease compared to the untreated group. Lipid peroxidation did not alter significantly in treated groups compared to the untreated group. For hematological and biochemical parameters, monocytes and alkaline phosphatase (ALP) levels decreased significantly in the rats that received high doses of Swedish bitters. Conclusion: Swedish bitters increased the activity of rat CYP2C9 significantly. Swedish bitters also altered the levels of catalase enzyme activity and reduced ALP levels, significantly. Findings suggest that Swedish bitters may interact with other drugs that are metabolized by these CYPs especially when taken over longer periods.