Nectandra as a renewable source for (+)-α-bisabolol, an antibiofilm and anti-Trichomonas vaginalis compound.

Essential oils, mixtures of volatile compounds, are targets of research for new antimicrobial drugs. In order to verify the potential from species of the Nectandra genus, the present study evaluated the essential oils from Nectandra amazonum, Nectandra cuspidata, Nectandra gardineri, Nectandra hihua and Nectandra megapotamica to prospect samples with high concentration of a component and its antibacterial, antibiofilm and anti-Trichomonas vaginalis activities. The essential oils from the leaves and barks were extracted by steam distillation and analyzed by gas chromatography coupled to mass spectrometry (GC-MS). The concentrations of 10 and 100 µg/mL of the essential oil were evaluated and the inhibition of bacterial growth and biofilm formation were measured, while for the evaluation of anti-T. vaginalis trophozoite viability, the concentrations from 7.8 to 1000 µg/mL were tested. Seventy-three compounds were identified from essential oils, highlighted bicyclogermacrene (up to 49.9%), elemicin (up to 42.4%), intermedeol (up to 58.2%), (E)-asarone (up to 45.9%) and (+)-α-bisabolol (up to 93.7%). The essential oil from N. megapotamica leaves presented 93.7% of (+)-α-bisabolol and demonstrated the high capacity of inhibition of the biofilm formation, in particular, against Staphylococcus aureus methicillin resistant (MRSA) and Pseudomonas aeruginosa. This sample also had significant activity against T. vaginalis (IC50 of 98.7 µg/mL) and demonstrated cytotoxic and hemolytic effects in Vero cells and human erythrocytes. In general, the Nectandra genus revealed high chemical variability and a N. megapotamica specimen accumulated a compound on high concentration with great potential for biotechnological exploration as a new antibiofilm and anti-T. vaginalis.

Anti-staphylococcal activity of Syagrus coronata essential oil: Biofilm eradication and in vivo action on Galleria mellonela infection model.

In this study, essential oil extracted from Syagrus coronata seeds (SCEO) was evaluated for antibacterial and antibiofilm activities against Staphylococcus aureus; in addition, Galleria mellonella model was used as an in vivo infection model. SCEO was mainly composed by fatty acids (89.79%) and sesquiterpenes (8.5%). The major components were octanoic acid, dodecanoic acid, decanoic acid and γ-eudesmol. SCEO showed bactericidal activity (minimal bactericidal concentration from 312 to 1250 µg/mL) against all tested S. aureus clinical isolates, which showed distinct biofilm-forming and multiple drug resistance phenotypes. SCEO weakly reduced biomass but remarkably decreased cell viability in pre-formed biofilms of S. aureus isolate UFPEDA-02 (ATCC-6538). Electron microscopy analysis showed that SCEO treatments decreased the number of bacterial cells (causing structural alterations) and lead to loss of the roughness in the multiple layers of the three-dimensional biofilm structure. In addition, overproduction of exopolymeric matrix was observed. SCEO at 31.2 mg/kg improved the survival of G. mellonela larvae inoculated with UFPEDA-02 isolate and reduced the bacterial load in hemolymph and melanization. In conclusion, SCEO is an antibacterial agent against S. aureus strains with different resistance phenotypes and able to disturb biofilm architecture. Our results show SCEO as a potential candidate to drug development.