Doctoral Thesis / Dissertation from the year 2012 in the subject Chemistry - Bio-chemistry, course: Biochemistry, language: English, abstract: Antioxidants are vital substances protecting cells from oxidative damage of biological molecules like DNA, proteins, lipids and maintain normal homeostasis in cell by scavenging free radicals. Oxidative stress is one of the major source of free radicals and causing disorders like multiple sclerosis, Alzheimer's, Parkinsons, cardiovascular diseases, and other degenerative disorders. Antioxidants finds application in medicine as they, act as immunoregulators, fight against ageing and also reported to induce apoptosis, cell cycle arrest against some cancer cell lines. Antioxidant also finds application in cosmetic industry and even as topical formulation. They are used as a preservative and also to increase the shelf life of frozen fish, canned mushrooms, meat, juice and general foods. Studies suggested that medicinal plants are a potential, inexpensive and safe source of antioxidants as they are enriched with bioactive compounds. Berberies aristata is commonly called as Daruhaldi or Chitra belongs to family Berberidaceae. The use of root extract as antipyretic, antiseptic, in the treatment of conjunctivitis, ulcers and hepatic disorders have been reported in earlier studies by various workers. The plant has been used for treatment of skin diseases, inflammation, diarrhoea and jaundice. Medicinal plants in the present study were screened for their antioxidant potential against different radicals like DPPH, superoxide, hydroxyl and peroxide. Among them ethanolic roots extract B.aristata exhibit highest antioxidant ability and least IC50 value. Thus further, the ethanolic root extract of B.aristata was subjected to activity guided isolation of antioxidants. Upon liquid-liquid fractionation ethyl acetate fraction exhibited highest radical scavenging activity against DPPH and peroxide radicals. In addition, the IC50 for DPP