Effects of glycyrrhetinic acid on aminonucleoside nephrosis in rats

Bioassays in natural product research - strategies and methods in the search for anti-inflammatory and antimicrobial activity

INTRODUCTION

Identifying bioactive molecules from complex biomasses requires careful selection and execution of relevant bioassays in the various stages of the discovery process of potential leads and targets.

OBJECTIVE

The aim of this review is to share our long-term experience in bioassay-guided isolation, and mechanistic studies, of bioactive compounds from different organisms in nature with emphasis on anti-inflammatory and antimicrobial activity.

METHODS

In the search for anti-inflammatory activity, in vivo and in vitro model combinations with enzymes and cells involved in the inflammatory process have been used, such as cyclooxygenases, human neutrophils and human cancer cell lines. Methods concerning adsorption and perforation of bacteria, fungi, human cells and model membranes, have been developed and optimised, with emphasis on antimicrobial peptides and their interaction with the membrane target, in particular their ability to distinguish host from pathogen.

RESULTS

A long-term research has provided experience of selection and combination of bioassay models, which has led to an increased understanding of ethnopharmacological and ecological observations, together with in-depth knowledge of mode of action of isolated compounds.

CONCLUSION

A more multidisciplinary approach and a higher degree of fundamental research in development of bioassays are often necessary to identify and to fully understand the mode of action of bioactive molecules with novel structure-activity relationships from natural sources.

[Protective effects of glycyrrhizin on adriamycin nephropathy in rats]

OBJECTIVE

To observe the effects of glycyrrhizin on laminin (LN) expression in kidney tissue and excretory quantity of urine protein of rats with adriamycin nephropathy, and to explore the protective effects of glycyrrhizin on glomerulosclerosis.

METHODS

Eighteen SD rats were randomly divided into 3 groups: normal control group (n=6), untreated group (n=6) and glycyrrhizin-treated group (n=6). Adriamycin nephropathy was induced in rats in the last two groups by intravenous injection of adriamycin. The rats in the glycyrrhizin-treated group were fed glycyrrhizin for eight weeks, whereas the rats in the normal control group and untreated group were fed normal saline solution for eight weeks too. The levels of 24 h urine protein (Upr), serum creatinine (sCr), blood urea nitrogen (BUN) and serum cholesterol (Ch) of rats in each group were examined before treatment and after the treatment for four and eight weeks. The renal morphological changes were observed under a microscope. The expression level of LN in renal tissue was detected by streptavidin-biotin peroxidase complex (SABC) method.

RESULTS

The levels of 24 h Upr after the treatment for four and eight weeks in the glycyrrhizin-treated group were both significantly decreased as compared with those in the untreated group. The pathological morphological changes of renal tissue in the glycyrrhizin-treated group were remarkably alleviated, and the expression level of LN in renal tissue was also decreased in the glycyrrhizin-treated group as compared with those in the untreated group.

CONCLUSION

The glycyrrhizin exerts certain protective effects on adriamycin nephropathy in rats by reducing excretory quantity of urine protein, decreasing expression level of LN in renal tissue, improving renal function and lessening the severity degree of glomerulosclerosis so as to retard the development of glomerulosclerosis.

Glycyrrhizae Radix attenuates peroxynitrite-induced renal oxidative damage through inhibition of protein nitration

We investigated the protective effects of Glycyrrhizae Radix extract against peroxynitrite (ONOO-)-induced oxidative stress under in vivo as well as in vitro conditions. The extract showed strong ONOO- and nitric oxide (NO) scavenging effects under in vitro system, in particular higher activity against ONOO-. Furthermore, elevations of plasma 3-nitrotyrosine levels, indicative of in vivo ONOO- generation and NO production, were shown using a rat in vivo ONOO(-)-generation model of lipopolysaccharide injection plus ischemia-reperfusion. The administration of Glycyrrhizae Radix extract at doses of 30 and 60 mg/kg body weight/day for 30 days significantly reduced the concentrations of 3-nitrotyrosine and NO and decreased inducible NO synthase activity. In addition, the nitrated tyrosine protein level and myeloperoxidase activity in the kidney were significantly lower in rats given Glycyrrhizae Radix extract than in control rats. However, the administration of Glycyrrhizae Radix extract did not result in either significant elevation of glutathione levels or reduction of lipid peroxidation in renal mitochondria. Moreover, the in vivo ONOO- generation system resulted in renal functional impairment, reflected by increased plasma levels of urea nitrogen and creatinine, whereas the administration of Glycyrrhizae Radix extract reduced these levels significantly, implying that the renal dysfunction induced by ONOO- was ameliorated. The present study suggests that Glycyrrhizae Radix extract could protect the kidneys against ONOO- through scavenging ONOO- and/or its precursor NO, inhibiting protein nitration and improving renal dysfunction caused by ONOO-.