The drinking of a Salvia officinalis infusion improves liver antioxidant status in mice and rats
Introduction
The oxidative damage of biological molecules is an important event in the development of a variety of human disorders that result from overwhelming the biological defense system against oxidative stress, drugs and carcinogens. The intake in the human diet of antioxidant compounds, or compounds that ameliorate or enhance the biological antioxidant mechanisms, can prevent and in some cases help in the treatment of some oxidative-related disorders and carcinogenic events (Havsteen, 2002).
Natural plant products have been used empirically for this purpose since ancient times and a tendency is emerging today for their increased use. Salvia officinalis L. (Lamiaceae) is a common aromatic and medicinal plant native from mediterranean countries that is in widespread use.
Experimental evidence already exists for a variety of bioactivities for different types of extracts of Salvia officinalis such as antioxidant, anti-inflammatory, hypoglycemic and anti-mutagenic activities (Cuvelier et al., 1994, Wang et al., 1998, Hohmann et al., 1999, Baricevic and Bartol, 2000, Baricevic et al., 2001, Zupko et al., 2001, Alarcon-Aguilar et al., 2002). However, the properties of sage infusion (hereafter, referred to as tea), the most common form of consumption of this plant, have received little attention.
Many bioactivities have been researched and detected in tea and in infusions (or water extracts) of other plants. Among them, the phenolic content of different plants have been shown to have antioxidant activities and the capacity to modulate xenobiotic metabolizing enzymes involved in drug and carcinogen activation and detoxification (Ferguson, 2001, Triantaphyllou et al., 2001). Several studies showed that black and green tea (Camellia sinensis) enhance phase II enzymes (Khan et al., 1992, Yu et al., 1997, Bu-Abbas et al., 1998). A water-soluble extract of rosemary also induced both phase I and phase II enzymes (Debersac et al., 2001a, Debersac et al., 2001b). However, the use of natural products may also result in toxic effects, which underscore the need to understand the biological effects of natural compounds. Toxic effects to the liver, the main xenobiotic metabolizing organ, are particularly relevant.
In the present study, we evaluate the biosafety and bioactivities of sage tea in vivo with mice and rats and in vitro using rat hepatocytes in primary culture. Toxic effects to the liver of sage tea drinking are tested in vivo on mice monitoring the plasma transaminase activities. The liver glutathione content and glutathione reductase (GR) and glutathione-S-transferase (GST) activities in the mouse livers and freshly isolated rat hepatocytes were also evaluated. In addition, primary cultures of hepatocytes isolated from sage tea and water drinking rats were challenged with the oxidant tert-butyl hydroperoxide (t-BHP) and the antioxidant protection conferred by sage tea drinking evaluated.
Section snippets
Chemicals
Collagenase (grade IV), tert-butyl hydroperoxide, glutathione reductase (EC 1.6.4.2.), 5,5′-dithio-bis-(2-nitrobenzoic acid) (DTNB), William's Medium E (WME) and Bradford reagent were purchased from Sigma (St. Louis, MO, USA). l-Lactate dehydrogenase (EC 1.1.1.27) and l-malate dehydrogenase (EC 1.1.1.37) were purchased from Roche (Germany). All others reagents were of analytical grade.
Plant material, preparation of sage tea and analysis of its phenolic and volatile compounds
Salvia officinalis L. plants were cultivated in an experimental farm located in Arouca, Portugal, and were
Phenolic and volatile compounds in sage tea
The infusion is composed of the phenolic compounds rosmarinic acid and four luteolin glycosides—luteolin-7-glucoside being the most representative flavone (Table 1), which constitutes 0.05% of total wet weight. In this sage infusion, we also identified 25 volatile compounds with 1,8-cineole, cis-thujone, trans-thujone, camphor and borneol being the most representative (85% of total volatile fraction). The most representative volatile compounds and their quantification are presented in Table 1.
Experiment 1
Discussion
The present study shows that sage tea drinking had no toxicity to the liver and no adverse effects on growth parameters neither in mice nor in rats. It also shows that sage tea drinking positively affected the antioxidant status of the liver, mainly the GST and GR activities of the mice livers and GST activity in rats.
The positive effects of sage tea drinking were also present in cultured hepatocytes. Immediately after isolation GST activity was higher in cells from sage tea drinking rats. At
Acknowledgments
CFL is supported by the Foundation for Science and Technology, Portugal, Grant SFRH/BD/6942/2001. This work was supported by FCT research Grant POCTI/AGR/43482/2001.
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