Reactive species are produced in biological system because of redox reactions. The imbalance in pro-oxidant and antioxidant homeostasis leads to the production of toxic reactive oxygen and nitrogen species like hydrogen peroxide, organic peroxides, hydroxyl radicals, superoxide anion and nitric oxide. Inactivation of metabolic enzymes, oxidation of biomolecules and cellular damage are some of the prominent characteristics of reactive species. Similarly, oxidative stress has been associated with more than one hundred (100) pathologies such as atherosclerosis, diabetes, cardiovascular diseases, pancreatic and liver diseases, joint disorders, cardiac fibrosis, acute respiratory distress syndrome, neurological diseases (amyotrophic lateral sclerosis, Huntington's disorder, Parkinson's disease and Alzheimer's disease), ageing and cancer etc. The toxicity of reactive species is balanced by the integrated antioxidant systems, which include enzymatic and non-enzymatic antioxidants. Antioxidant therapies or defenses protect the biological sites by removing or quenching the free radicals (prooxidants). Medicinal plants can not only protect the oxidative damage, but also play a vital role in health maintenance and prevention of chronic degenerative diseases. This review will provide a valuable discussion of one hundred (100) well known medicinal plants, which may add to the optimization of antioxidants rank. Besides, some of the antioxidant evaluation techniques or mechanisms via which medicinal plants act as antioxidants are also described.

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A simple and sensitive stability indicating HPLC-UV method was developed for the analysis of process impurities and degradation products in Sofosbuvir and Velpatasvir pharmaceutical formulations. Analysis was performed on C18 analytical column (250 mm 4.6 mm, 5 m), using a mobile phase of 0.05M ammonium acetate buffer (pH 6.5) with acetonitrile at 45 : 55 (v/v) ratio and a flow rate of 1.0 mL/min. The detection wavelength for simultaneous determination of both ingredients using UV detector was 268 nm. The method was validated for accuracy, precision, linearity, and specificity using reference standards of process impurities and degradation products. The calibration curve was linear and the limits of detection and quantification were determined using 3 /slope and 10 /slope expressions, respectively. Forced degradation studies for Sofosbuvir and Velpatasvir drug substances and products were designed under different environmental stress conditions. The effect of alkaline, acidic, oxidative, and thermal stress conditions on Sofosbuvir and Velpatasvir substances and dosage forms was studied. The influence of heat and humidity was studied at 80 5°C and 75 5% RH. Similarly, the photolytic studies were performed on visible light at 200 W h/m 2 UV and 1.2 million lux h/m 2 in a climatic chamber. The proposed method is stability-indicating and has been successfully applied to the analysis of process impurities and degradation products in Sofosbuvir and Velpatasvir pharmaceutical formulations. The degradation products were characterized by MS, NMR and IR spectroscopy analysis for identification of degradation products and determination of mechanisms.