Antioxidant ability and total phenolic content of aqueous leaf extract of Stevia rebaudiana Bert

Approximately 80% of the world populations depend exclusively on plants for their health and healing. Whereas in the developed world, reliance on surgery and pharmaceutical medicine is more usual however in the recent years, more and more people are complementing their treatment with natural supplements. Nowadays motivation of people towards herbs is increasing due to the concern about the side effects of synthetic chemical drugs. People want to concern their own health rather than submitting themselves to impersonal health care system. Many herbal and some common medicinal plants are good sources of antioxidant compounds. Many of the biologically active substances found in plants, including phenolic compounds (flavonoid, phenolics) are known to possess potential antioxidant properties. The antioxidant activity of medicinal plants depends on the concentration of individual antioxidant entering into the composition.

Antioxidants are micronutrients that have gained importance in recent years due to their ability to neutralize free radicals. Free radicals have been implicated in the etiology of several major human ailments including cancer, cardiovascular diseases, neural disorders, diabetes and arthritis. Antioxidants have been reported to prevent oxidative damage caused by free radical, they can interfere with the oxidation process by reacting with free radicals, chelating, catalytic metals and also by acting as oxygen scavengers. The potentially reactive derivatives of oxygen, attributed as reactive oxygen species (ROS), are continuously generated inside the human body which are detoxified by the antioxidants present in the body. However, overproduction of ROS and/or inadequate antioxidant defense can easily affect and persuade oxidative damage to various biomolecules including proteins, lipids lipoproteins and DNA. This oxidative damage is a critical etiological factor implicated in several chronic human diseases such as diabetes mellitus, cancer, atherosclerosis, arthritis and neurodegenerative diseases as well as ageing process.