PRELIMINARY PHYTOCHEMICAL SCREENING AND IN-VITRO EVALUATION OF ANTIOXIDANT ACTIVITY OF IRAQI SPECIES OF SILYBUM MARIANUM SEEDS

Abstract

Silybum marianum is medicinally important plant species from Asteraceae family. It has been used for centuries as a herbal medicine for the treatment of many diseases particularly liver diseases. In the present work the seeds of the plant were extracted by two methods: maceration using 80 % ethanol and soxhlet extraction using petroleum ether and methanol, respectively. Fractional separation of ethanolic extract was carried out using solvents with various polarities like: petroleum ether, chloroform, ethyl acetate and n-butanol. Ethanolic extract was subjected to phytochemical screening to detect the presence of bioactive compounds. The study revealed the presence of flavonoids, phenols, tannins, terpenoids, carbohydrates and proteins. All fractions and extracts were subjected to TLC analysis to determine the phytochemical compounds. Results of the retention factor (Rf) obtained were compared with that of the silymarin standard TLC system. The TLC finger print of the methanolic, ethanolic extracts and ethyl acetate fraction using the solvent system chloroform : acetone : formic Acid (75: 16.5:8.5), showed the spots having Rf = 0.63, 0.4, 0.35 which was equivalent to silybin, taxifolin and silichristin, respectively. Evaluation of antioxidant activity was carried out by two methods, the free radical scavenging activity of the 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH), and total antioxidant capacity (TAC) by the phosphomolybdenum method. Estimation of total phenolic contents was performed using Folin-Ciocâlteu method. Antioxidant assays revealed that ethyl acetate fraction exhibited highest percent inhibition of DPPH followed by methanolic and ethanolic extracts. It also showed the highest value of total antioxidant capacity as well as highest amount of total phenolic compounds. Our findings revealed that Iraqi species of Silybum marianum seeds can be considered as a valuable source of natural antioxidants which may be attributed to the presence of silymarin a powerful antioxidant herbal drug which can protect biological systems against the oxidative stress.