The Importance of Monoterpenes in the Antibacterial Activity of Osteophloeum platyspermum Essential Oils

Aims: To evaluate antibacterial and cytotoxic activities of essential oils (EO’s) obtained from Osteophloeum platyspermum (ucuuba-chico-de-assis; Myristicaceae) fresh leaves against Staphylococcus aureus, MCF-7 breast, and PC-3 prostate cancer cell lines. Study Design: Thirteen EO's were submitted to antibacterial and cytotoxicity assays that included 18 compounds commonly present in the EO's. The relationship between the EO's biological activities and the dry (DS) or rainy (RS) seasonal variation was accessed using the relative percentage of the terpenes. Place and Duration of the Study: The study was conducted at the Center for Research in Biodiversity (Microbiology Laboratory and Cell Culture Laboratory), Paulista University. Biological activity assessment was conducted between October/2016 and November 2019). Methodology: Thirteen essential oils were obtained from the leaves of O. platyspermum and were previously chemically characterized. From the analyses, 18 terpenes were determined to commonly occur in the 13 EO's. Microdilution broth and cytotoxicity assays were performed to obtain minimal bactericidal concentrations (MBCs) and 50% (EC50) effective concentrations for the cytotoxicity assays. Data from the 18 terpenes were submitted to two-way ANOVA, cluster (CA), principal component (PCA), canonical correspondence analyses (CCA), and one-sample t-test. The relationship between the biological activities of EO's and seasonal variability (dry season, DS, or rainy season, RS) was assessed. One sample t-test was performed to verify the potency of the cytotoxic effects of EO’s. Results: Previously, 18 terpenes were identified in all the 13 EO’s. From those, α-terpineol, limonene, myrcene, linalool, and terpinen-4-ol were relevant to the ordination of the DS EO set, while spathulenol, α-pinene, β-pinene, isospathulenol, α-cadinene, ledol, cubenol-1-epi, neo-intermedeol, elemol, β-elemene, γ-elemene and viridiflorol were relevant to the ordination of the RS EO set. The biological activities were more related to the EO’s collected in the RS than those in the DS. Also, biological activities were shown to be related to the occurrence of limonene, myrcene, elemol, β-pinene, α-pinene, and terpinen-4-ol. Conclusions: Although the presence of the 18 terpenes is necessary to maintain the species adaptability to the environment, the occurrence of limonene, myrcene, elemol, β-pinene, α-pinene, and terpinen-4-ol had a significant role in the effective expression of the biological activity of EO’s from O. platyspermum, particularly those that occur during the rainy season, in the Amazon rain forest.