Screening and mechanistic study of estradiol-stimulating fractions derived from erxian decoction in aged sprague-dawley rats

Abstract

BACKGROUND: Erxian Decoction (EXD), a famous herbal formula, has been used to relieve menopausal syndrome for more than 60 years. Our previous study firstly reported that EXD could promote estradiol biosynthesis in vivo via up-regulation of ovarian aromatase, but it is still unknown which components from EXD promote estradiol biosynthesis. OBJECTIVES: To screen the effective fraction extracted from EXD which promotes estradiol biosynthesis in vivo. METHODS: Four bioactive fractions derived from aqueous EXD decoction, i.e. polysaccharide fraction (PS), ethyl acetate fraction (EA), n-butanol fraction (BU) and water faction (WA), were subsequently extracted by solvent partition method. The polysaccharide fraction (PS) was obtained from the total aqueous decoction (TW) of EXD by precipitation with 75% ethanol overnight at 4℃. After filtration, the residue was the total EXD ethanol extract. The total EXD ethanol extract was extracted with three volumes of ethyl acetate at room temperature to yield the EA. The fraction which remained was processed with three volumes of n-butanol at room temperature to yield the BU and the fraction which remained was WA. Each of the above fractions (PS, EA, BU and WA) together with the EXD (TW) were dried to powder form using a freezer dryer. Then the powders from the five fractions were dissolved in Milli-Q water for oral administration into SD rats (≧ 18 months) for 4 weeks. The concentrations of powders per body weight of SD-rat were calculated according to their recovery rates, they are shown as follows: TW = 4.10g/kg, PS = 1.64g/kg, EA = 0.11g/kg, BU = 0.47g/kg and WA = 2.34g/kg. RESULTS: The serum estradiol level in PS-treated aged SD-rats was the highest compared with other groups. PS also enhanced the protein expression of FSHR and aromatase in the ovaries of SD rats. CONCLUSION: Polysaccharide is the main component from EXD which stimulated estradiol biosynthesis. Its mechanism is mainly via up-regulating the FSHR and aromatase expression in the ovary. Thus polysaccharide from EXD could be used as an alternative treatment for relieving menopausal syndrome.