Orbital: The Electronic Journal of Chemistry journal homepage: www.orbital.ufms.br ISSN 1984-6428  Vol 6   No. 4   October-December 2014  Full Paper * Corresponding author. E-mail: warley.borges@ufes.br In vitro antioxidant and cell viability of Pyrostegia venusta (Ker Gawl.) Miers) Thales D. P. Altoé a , Gustavo M. de Amorim b , João Victor D. Gomes b , Augusto S. Borges b , Iuri C. Valadão b , Ian Victor Silva c , Letícia B. De A. Rangel b , Paulo Cezar Vieira d , Claudia M. Jamal b , Rodrigo R. Kitagawa b , Warley de S. Borges a,* a Department of Chemistry, Exact Sciences Center, Federal University of Espírito Santo (UFES), 29075- 910,Vitória, ES, Brazil. b Department of Pharmaceutical Sciences, Health Sciences Center, Federal University of Espírito Santo (UFES), 29040-090,Vitória, ES, Brazil. c Department of Morphology, Health Sciences Center, Federal University of Espírito Santo (UFES), 29040- 090,Vitória, ES, Brazil. d Department of Chemistry, Federal University of São Carlos (UFSCar), 13565-905, São Carlos, SP, Brazil. Article history: Received: 24 July 2014; revised: 13 November 2014; accepted: 18 November 2014. Available online: 30 December 2014. Abstract: Many diseases are associated with oxidative stress and inflammatory processes. The current research is directed toward evaluating the antioxidant potential and phytochemistry composition of P. venusta leaves. In this study, P. venusta leaves were dried and macerated, and the crude extract was partitioned. Phytochemical analysis was performed using standard methodologies, and the total flavonoid content was measured using a calibration curve with rutin. We evaluated the antioxidant potential of P. venusta leaves using 1,1-Diphenyl-2- picrylhydrazyl (DPPH), 2, 2’-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), and a Trolox-like standard. Cell viability (CV) assays were done using macrophage RAW 264.7 cell lines and compared to four commercial anti-inflammatories (acetylsalicylic acid, Indometacina, Betametasona, and Piroxicam). Phytochemical analysis revealed the presence of steroids, coumarins, and flavone. The flavonoid content was 148.5 ± 7.65 µg as a rutin equivalent/mg of crude extract. The ethyl acetate fraction showed the best antioxidant activity in the methodologies of DPPH inhibition (IC50 = 38.62 µg/mL) and ABTS radical (IC50 = 28.58 µg/mL). Samples of P. venusta had CV values that were better than the commercial anti-inflammatory, which showed CV values below the negative control. The crude extract and the ethyl acetate fraction, showed CV values below the negative control and the hexane fraction obtained values above the negative control, these being best results. Keywords: Pyrostegia venusta; leaves; antioxidant; DPPH; ABTS; cell viability 1. INTRODUCTION Oxygen is essential for many biological process, including the production of energy in heterotrophic organisms (Kreb’s Cycle) and others involved in electron transfer [1-2]. This process results in free radicals and other compounds like reactive oxygen species (ROS). The body naturally neutralizes this species, but the imbalance between neutralization and formation can induce oxidative damage to biomolecules, known as oxidative stress [1, 3-5]. Many diseases such as cancer, diabetes mellitus, cardiovascular diseases, degenerative disorders, arthrosclerosis, and inflammatory diseases are reported to involve this imbalance of free radicals [1, 6-8]. During an inflammatory process, an organism causes an oxidative stress for defense, known as a respiratory burst [9, 10]. The phagocytic leukocytes (macrophages, neutrophils and eosinophils), when activated by a pro- inflammatory mediator, are the most likely sour ce of ROS. Initially, an NADPH oxidase catalyzes a large amount of superoxide radical (O2•) production; this reactive species is used in enzymatic reactions to produce other ROS like HClO (hypochlorous acid), H2O2 (hydrogen peroxide), and OH• (hydroxyl radical), and these ROS kill pathogens as well as