First report on the chemical composition of leaf essential oil of Myrciaria pilosa Sobral & Couto and its antimicrobial and antivirulence activities against Staphylococcus aureus.

Myrciaria pilosa is a tree species of the Brazilian Caatinga biome. This paper is the first report on the chemical composition and the antimicrobial and antivirulence activities of essential oil extracted from its leaves. The oil was extracted by hydrodistillation. Chemical composition determined by GC-MS and CG-FID revealed 63 compounds; the sesquiterpenes guaiol (13.17%) and (E)-ß-caryophyllene (11.26%) dominated. Antimicrobial activity against strains of Staphylococcus aureus was evaluated by the broth microdilution method. It showed minimum inhibitory concentrations (MIC) of 5 µg/mL against evaluated strains and minimum bactericidal concentrations (MBC) ranging from 10 to 20 µg/mL. Evaluation of antivirulence activity showed reductions of 92.0% and 47.2%, respectively, in haemolytic action and production of staphyloxanthin. These findings show that the essential oil of M. pilosa has potential as an antimicrobial drug to control infection by multi-resistant strains of S. aureus.

Chemical composition, antioxidant and antiprotozoal activity of Eugenia gracillima Kiaersk. leaves essential oil.

This work evaluated the volatile composition, antioxidant and antiprotozoal activities of the essential oil obtained from leaves of Eugenia gracillima Kiaersk. (EGEO) grown in Brazilian Northeast area (Araripe, Brazil). The volatile compounds of EGEO were analyzed by GC and GC-MS and its chemical composition is mainly composed of sesquiterpene hydrocarbons (91.22%), oxygenated sesquiterpenes (7.45%) and monoterpene (1.01%). The most abundant volatile constituents of the EGEO were germacrene D (16.10%), γ-muurolene (15.60%), bicyclogermacrene (8.53%), germacrene B (7.43%), and Δ-elemene (6.06%). The oil showed weak to moderate antioxidant activity. EGEO was highly selective to Leishmania braziliensis and Leishmania infantum promastigotes with selective indexes of 73.66 and 71.41, respectively. EGEO did not inhibit Trypanosoma cruzi. These data suggest that the E. gracillima essential oil is a relevant source of lead compounds for development of anti-Leishmania drugs.

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.