EFFECT OF SEED EXTRACT OF MILK THISTLE SILYBUM MARIANUM L. ON SOME BACTERIAL ISOLATES

Abstract

Silybum marianum (L). Gaertn is a herb which may be annual or biennial. It is widely distributed in sub-tropical and temperate areas of the world. Silybum marianum is commonly known as “Milk Thistle”. It belongs to family Asteraceae and contains various flavonolignans; most important of them is silybin. These flavonolignans are medicinally important as they are used as anti-toxins, antispasmodic, anti-allergic, anti-oxidants and anti-fungal agents etc. The plant is also grown commercially in various parts of the world. Various studies have shown that extract of the plant has antibacterial activity against various species of bacteria. Two bacterial species Staphylococcus aureus and Camomonas kerstersii were tested for the antibacterial activity of the seed extract from the plant through agar well diffusion method. Seed extract of the plant showed high antibacterial activity against gram positive bacterium Staphylococcus aureus with a zone of inhibition of 8.0 mm² for the aqueous extract with a concentration of 100 mg/ml and 12.0 mm² for the methanolic extract with a strength of 100 mg/ml while gram negative bacterium Camomonas kerstersii was found to be resistant against the methanolic as well as aqueous extract. An antibiotic Gentamycin used as a control to check the effectiveness of the experiment which showed a zone inhibition of 18.0 mm² for the Staphylococcus aureus and 17.0 mm² zone of inhibition for Camomonas kerstersii. Our study has shown that the methanolic extract from the Milk thistle seeds was more effective against Staphylococcus aureus and less effective against Camomonas kerstersii. Silybum marianum may be used as an effective antibacterial agent, was shown by this study.