Andrographis paniculata Nees is an annual herbaceous plant which belongs to the family Acanthaceae. It is commonly known as Kalmegh, is found in the plains of India, China, Pakistan, Sri Lanka and South Asia and is native to India and Sri Lanka. Kalmegh is known to be the "king of bitters" though it is of small size and it also has a similar appearance and taste as that of the Neem plant. It is one of the widely used effective medicinal plants in the world. All parts of this plant are used to extract the potential phytochemical, but the composition of phytoconstituents mostly differs from one part to another in a season, place and time of harvest. It is a traditional medicinal plant widely used in the treatment of anti-inflammatory, anti-bacterial, anti-oxidant, hepatoprotective, hematocidal, anti-HIV, anticancer, anti-diabetic, arthritis, rheumatism, cough, cold, multiple sclerosis, depression, diarrhoea, dysentery, candida, fevers, herpes, leprosy, malaria, jaundice, tuberculosis and several infectious diseases ranging from malaria to dysentery. The plant is widely used in Ayurvedic and homeopathic system of medicine. The medicinal value of this plant is due to the active ingredients via andrographolide and neoandrographolide, which are derivative of diterpinoids. It prevents oxidative damage and inhibits binding of toxic metabolite to DNA.

The present investigation aimed to identify the effects of ethanolic extract of <i>Andrographis paniculata</i> Linn. and <i>Rhinacanthus nasutus</i> Kurz. on enzymatic and non-enzymatic antioxidants on isoniazid and rifampicin induced Wistar rats. Animals were randomly divided into nine groups of 6 rats each and housed in individually ventilated cages for further experimental procedure. The levels of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), glutathione-s-transfersase (GST), lipid peroxides (LPO), reduced glutathione (GSH), vitamin C (vit C) and vitamin E (vit E) and carbohydrate metabolism parameters of glucose, glycogen, glucose-6-phosphatase, glucose-6-phosphatase dehydrogenase and hexokinase are estimated at the end of the study. The present study results highlighted that the leaves extract of <i>A. paniculata</i> and <i>R. nasutus</i> have an antioxidant effect and anti-diabetic activity against the toxin treated rats.

Plants are adundantly and are very promisive to be used as source of drugs in many diseases or infections and also it is a main agents of antioxidants which prevents the oxidative stress that are caused by the free radicals. There are numerous studies based on the pharmaceutical and classification of medicinal plants throughout the world. Leaves, fruits, roots are most frequently plant parts used in many research and studies. Here the present study was aimed to evaluate the in vitro antioxidant activity of aqueous and ethanol leaf extracts of Andrographis paniculata Nees and Rhinacanthus nasutus Kurz. Antioxidant is a substance which is used to prevent some types of cell damage in the body. Determination of their in vitro antioxidant activity were carried out by using methods such as DPPH (2,2-diphenyl-1picrylhydrazyl assay), ABTS (2,2′-azinobis (3-ethylbenzothiazolin 6-sulfonic acid assay), FRAP (ferric reducing antioxidant power assay) and SOD (super oxide anion scavenging) assay, H2O2 (hydrogen peroxide radical scavenging) assay. Moreover the ethanolic leaf extracts showed best antioxidant activity than the aqueous leaf extracts. Experimental results reveals that the leaves of A. paniculata have potent antioxidant and free radical scavenging activity than R. nasutus. Further investigation must be done for these two medicinal plants for the discovery of the bioactive compounds.