Evaluation of Phytochemicals and Biological Activity of Silybum marianum L.

Aims: The goal of this work is the evaluation of phytochemicals and biological activity of Silybum marianum.

Place and Duration of Study: S. marianum L. and seeds of Chenopodium murale L. were collected from different sites from Al Anbar, Iraq during the period of May 2017.

Methodology: Total phenolics, tannins, alkaloids, flavonoids and saponins, were determined. The antioxidant activity was measured based on the reduction of DPPH (1,1-diphenyl-2-picrylhydrazyl). Antibacterial activity of the extracts was determined against ten microorganisms using the disc diffusion method as well as the allelopathic potential of the S. marianum extract on the germination of C. murale was studied.

Results: The IC50 values of Methanol extract of S. marianum extracts had the highest scavenging activity (1.99 mg.ml-1). The radical scavenging activity of the other extracts and standard decreased in the following order: catechol, ethyl acetate, hexane and petroleum ether. In the present study the S. marianum extracts exhibited different inhibitory activities against the tested microorganisms with different degrees, methanol and ethyl acetate extracts of S. marianum showed the broad spectrum against the tested microorganisms. The pathogen Escherichia coli was the most sensitive bacteria (25 mm), while Aspergillus fumigatus and A. niger were the most sensitive fungi (25 and 27 mm) in case of methanol extract. The phytotoxicity of S. marianum extracts was increased significantly with the increasing extract concentrations. At 25 g.l-1 and 20 g.l-1 the germination of C. murale was reached maximum inhibition (92.45% and 76.84, respectively). In case of C. murale radicle growth, the higher concentration (25 g.l-1) was strongly inhibited (97.23%) the C. murale. Similarity, the plant extract significantly reduced the plumule length of C. murale. The highest concentrations (25 g.l-1) of extract showed strong inhibition (87.29%) of plumule growth.

Conclusion: S. marianum extracts can be used as natural antioxidant, antimicrobial agents pharmaceutical and bio-control of weeds.