Recebido em 20/3/12; aceito em 26/7/12; publicado na web em 7/12/12Aloysia gratissima (Gill. et Hook) Tronc. (Verbenaceae) is native to South America with folk therapeutic applications for a wide range of diseases. The polyphenolic and carotenoid profile, toxicity, and antioxidant activity of aqueous extract of Aloysia gratissima were investigated. HPLC analyses showed high amounts of ferulic acid, trans-cinnamic acid and p-coumaric acid, and also transb-carotene and lutein which fluctuated throughout the seasons. Furthermore, the extract investigated not only exerted antioxidant activity but also inhibited lipid peroxidation. Toxicity was achieved only at the highest dose tested. Therefore, A. gratissima is a potential species for medicinal purposes.Keywords: Aloysia gratissima; Verbenaceae; antioxidant activity. INTRODUCTIONAloysia gratissima (Gill. et Hook) Tronc. (Verbenaceae) is an aromatic native plant widely distributed in subtropical regions of South America, particularly Brazil, Paraguay, and Argentina. In Brazil, its folk name is "erva-santa", popularly named by local communities that use its aqueous extract to which they attribute several therapeutic benefits. In traditional medicine, it is thought to be a remedy to alleviate and help treat symptoms associated with headaches, bronchitis, and nervous system disorders 1 including depression 2 and also to treat digestive system disorders. 3 However, there are no published studies investigating Aloysia gratissima's toxicity while scientific articles about its chemical composition or antioxidant action are scarce, with those available focusing mainly on aqueous extract. Thus, while the chemical composition and some biological activities 4 of Aloysia gratissima's essential oil have been investigated, information on the bioactive compounds belonging to the aqueous extract, to the best of our knowledge, has not yet been described. Furthermore, there is a lack of information about the seasonal phytochemical profile of Aloysia gratissima's aqueous extract.The methanolic extract of A. gratissima has shown the presence of kauranes, flavonoids and phenylethanoids 5 in addition to α-bisabolol, triterpenes such as α-amirin, the acids betulinic, oleanolic and ursolic, flavonoids such as genkwanin, 5-hydroxy-7,4'-dimethoxyapigenin, 5-hydroxy-7,3',4'-trimethoxyluteolin, and rutin, which exhibited antibacterial, antiedematogenic, and antioxidant properties. 6 Recently, Zeni et al. 7 demonstrated that Aloysia gratissima's aqueous extract has both antidepressant-like and neuroprotective effects in mice.Polyphenols and carotenoids have been studied as factors responsible for treating several cardiovascular and neurodegenerative diseases and cancer. 8 The aim of this study was to determine the polyphenolic and carotenoid composition of the plant throughout the seasons; to select the aqueous extract with the highest level of those compounds, and to investigate the toxicity and antioxidant activity of the aqueous extract containing the highest level of bioactive compounds an...