The sensitize the central neurons in the nociceptive

The oxidation of biological molecules by the oxidative stress is involved in numbers of diseases including neurodegenerative, cardiovascular, cancer, hepatic and renal disease. (Losada-Barreiro et al., 2017). Oxidative stress is caused by the highly energetic, chemically unstable and very reactive chemical species having a single unpaired electron known as free radicals (Togo, 2004). When free radicals are produced in foods or biological tissues, they react readily with biomolecules such as lipids, carbohydrates, proteins and nucleic acids, producing different non-radical and radical species which are responsible for disease state in humans (Rosini et al., 2013). Antioxidants scavenge the free radicals and restore damaged target molecules (Shahidi, 2015).

Inflammation is the immune system’s response to infection and injury and has been implicated in the pathogenesis of sepsis, severe burns, arthritis, cancer, stroke, as well as in neurodegenerative and cardiovascular disease (Nathan, 2002). Inflammatory mediators play a key role in the manifestation of many clinical conditions such as pain and pyrexia. Thermal, chemical and/or mechanical injuries have the potential for releasing most of the inflammatory and chemical mediators that produce sensitization and excitation of nociceptors, which sensitize the central neurons in the nociceptive pathway inducing the pain and hyperalgesia (Pedersen, 2000). Pyrexia which is associated with the enhanced release of pyrogens; interleukins, interferon induced the synthesis of prostaglandin E2 (PGE2) from hypothalamus resulting hyperthermia (Dinarello, 2004). Non-steroidal anti-inflammatory drugs (NSAIDs), opioids, and corticosteroids are the available therapeutic agents to treat inflammation and its associated disorders.

World Health Organization estimates up to 80 % of the population in developing countries relies on traditional and botanical medicine as a primary source of health practice (Eskinazi, 2001). The investigation of plants for their medicinal use has been practiced by many cultures from antiquity. Given their extensive range of knowledge on medicinal plants utilization, indigenous people remain the ultimate resource for retrieving information for the purpose of the application, particularly in modern medicine (Idu, 2009). Research on plants based medicine practiced by indigenous people is playing the virtuous role in drug discovery (Pan et al., 2014). However, in absence of proper documentation, many traditional methods and knowledge of medicinal flora are being lost (Correa, 2002).

Pogostemon bengalensis (P. bengalensis) is a perennial aromatic shrub belonging to family Lamiaceae, which is distributed from 150-1300 meter altitude (Uprety et al., 2016). It is commonly called “Rudhilo” in Nepal (Dangol, 2002). Traditionally, plant leaves were inhaled and applied on the forehead for a cough, cold, and headache (Ghimire et al., 2009). Whereas,  juice was used to relieve fever (Manandhar, 1989).  Plant juice was mixed with year old cow dung and given to cattle to control dysentery (Manandhar, 1985), whereas root juice was used for indigestion (Quattrocchi, 2012). Additionally, young shoots were grounded and given to treat a sore throat (Siwakoti et al., 2000). P. bengalensis extract has reported the presence of flavonoids, alkaloids, saponins, phenolic compounds, terpenoids, and steroids as the principal active ingredients (Patel et al., 2014). Moreover, other phytochemicals reported were cadinene isomer, elemol, ?-bulnesene, ?-elemene and germacrene-D in leaf oil and  caryophyllene, germacrene-B, ?-cadiuene, ?-ocimene, ?-elemene, caryophyllene oide, curzerene, ?-humulene, ?-guaiene and germacrene in inflorescence oil (Bhuiyan et al., 2011). Pharmacologically, the plant has been reported for antimicrobial activity against bacteria  including E. coli, S. aureus, P. vulgaris and A. parasiticus, antifungal against C. albicans (Thoppil et al., 2014) and antiviral against Sindbis virus. (Taylor et al., 1996). Recently plants extract was investigated on ehrlich ascites carcinoma (EAC) tumor-bearing mice, which showed significant antitumor activity (Patel et al., 2014).  

Despite the ethnopharmacological use of P. bengalensis for treatment of fever and pain, its systematic scientific evaluation has not been carried out till date. Therefore, the present study was designed to scientifically evaluate the antioxidant, analgesic and antipyretic activities of P. bengalensis leaves extract.