Phytochemical study of P. lanceifoluim, used in the traditional medicine in the South of Ecuador, resulted in the isolation of one flavone called Sakuranetin (1), two benzoic derivative acid knows called: lanceaefolic acid methyl ester (2), and cyclolanceaefolic acid methyl ester (3). The structures of compounds were established by means of 1H- and 13C-NMR and MS data, and compared with literature data. The essential oils were obtained by hydrodistillation and then analysed by gas chromatography/flame ionization detector (GC/FID) and gas chromatography/mass spectrometry (GC/MS), a total of 35 constituents were identified, representing the 97.3% of the chemical composition. Safrole was the most abundant compound in the plant with 48.3%. Monoterpene hydrocarbons and oxygenated monoterpenes are the most important groups of compounds in the essential oil of P. lanceifolium, this oil exhibited a moderate antibacterial effect against Klebsiella pneumoniae (ATCC 9997).