Role of estrogenic receptors and oxidative stress on protective effect of aqueous extract of Silybum marianum in hemi-parkinsonian rat

Vegetable phenols can act as potent antioxidants. Silybum marianum has abundant amount of phenols which their interaction with estrogenic receptors has also been reported. This study was performed with the aim of investigating the role of estrogenic receptors and oxidative stress in protective effect of aqueous extract of Silybum marianum in hemiparkinsonian rats. In this experimental study 60 male rats were randomly divided into 6 groups including control, extract-treated control, extract and fulvestrant (estrogenic receptors antagonist) treated control, lesioned, extract-treated lesioned and extract and fulvestrant-treated lesioned groups. Two weeks after stereotaxic surgery, the animals were tested for rotational behavior by apomorphine, the number of neurons in the substantia nigra pars compacta (SNC), the concentration of malondialdehyde and amount and activity of superoxide dismutase (SOD). Data were analyzed using descriptive statistics and one-way ANOVA, T-test and Tukey’s post-test by SPSS 13. In the lesioned group, apomorphine caused a significant contra-lateral turning and reduction in the number of neurons on the left side of SNC (p<0.0001). A queous extract of Silybum marianum caused a significant reduction in contra-lateral turning (p<0.05) and reduced of the number of neurons on the left side of SNC in lesioned group (p<0.05) and caused a reduction in malondialdehyde production and increased the activity level of SOD (p<0.05, p<0.01). Fulvestrant decreased the protective effect of extract on rotation behavior, the number of SNC and biochemical factors in brain tissue (p<0.05). It seems that the protective effect of Silybum marianum extract against 6-hydroxydopamine is partially mediated by reduction of oxidative stress and also through estrogenic pathway.