Chemical composition and <i>in vitro</i> antibacterial and antiproliferative activities of the essential oil from the leaves of <i>Psidium myrtoides</i> O. Berg (Myrtaceae)

<p>In this study, the chemical composition and antibacterial and antiproliferative potential of the essential oil obtained from fresh leaves of <i>Psidium myrtoides</i> (PM-EO) against oral pathogens and human tumour cell lines were investigated for the first time. GC-FID and GC-MS analyses showed that <i>trans</i>-β-caryophyllene (30.9%), α-humulene (15.9%), α-copaene (7.8%), caryophyllene oxide (7.3%) and α-bisabolol (5.3%) are the major constituents of PM-EO. The antibacterial activity of PM-EO against a panel of oral pathogens was investigated in terms of their minimal inhibitory concentrations (MIC) using the broth microdilution method. PM-EO displayed moderate activity against <i>Streptococcus mitis</i> (MIC = 100 μg/mL), <i>S. sanguinis</i> (MIC = 100 μg/mL), <i>S. sobrinus</i> (MIC = 250 μg/mL), and <i>S. salivarius</i> (MIC = 250 μg/mL), and strong activity against <i>S. mutans</i> (MIC = 62.5 μg/mL). The antiproliferative activity in normal (GM07492A, lung fibroblasts) and tumour cell lines (MCF-7, HeLa, and M059 J) was performed using the XTT assay. PM-EO showed 50% inhibition of normal cell growth at 359.8 ± 6.3 μg/mL. Antiproliferative activity was observed against human tumour cell lines, with IC₅₀ values significantly lower than that obtained for the normal cell line, demonstrating IC₅₀ values for MCF-7 cells (254.5 ± 1.6 μg/mL), HeLa cells (324.2 ± 41.4 μg/mL) and M059 J cells (289.3 ± 10.9 μg/mL). Therefore, the cytotoxicity of PM-EO had little influence on the antibacterial effect, since it showed antibacterial activity at lower concentrations. Our results suggest that PM-EO is a promising source of new antibacterial and antitumour agents.</p