In this study, we performed the chemical characterization of Myrcia splendens (Sw.) DC. (Myrtaceae) essential oil from Amazonian Ecuador and the assessment of its bioactivity in terms of cytotoxic, antibacterial, and antioxidant activity as starting point for possible applicative uses. M. splendens essential oil, obtained by hydro-distillation, was analyzed by Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Flame Ionization Detector (GC-FID): the major components were found to be trans-nerolidol (67.81%) and α-bisabolol (17.51%). Furthermore, we assessed the cytotoxic activity against MCF-7 (breast), A549 (lung) human tumor cell lines, and HaCaT (human keratinocytes) non-tumor cell line through 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) test: promising results in terms of selectivity and efficacy against the MCF-7 cell line (IC50 of 5.59 ± 0.13 μg/mL at 48 h) were obtained, mainly due to α-bisabolol. Furthermore, antibacterial activity against Gram positive and negative bacteria were performed through High Performance Thin Layer Chromatography (HPTLC) bioautographic assay and microdilution method: trans-nerolidol and β-cedren-9-one were the main molecules responsible for the low antibacterial effects against human pathogens. Nevertheless, interesting values of Minimum Inhibitory Concentration (MIC) were noticeable against phytopathogen strains. Radical scavenging activity performed by HPTLC bioautographic and spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) approaches were negligible. In conclusion, the essential oil revealed a good potential for plant defense and anti-cancer applications.

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Bioautography has been used as rapid and easy strategy to detect and identify bioactive fractions/molecules in the never before investigated Hedyosmum sprucei Solms (Chloranthaceae) essential oil (EO). The antioxidant activity, performed through DPPH bioautographic assay and spectrophotometric evaluations (IC50 = 230 ± 10 µg/mL), seemed to be mainly due to α-cadinol and α-muurolol. (HP)TLC bioautography, focused on antimicrobial capacities, pointed out α-cadinol, α-muurolol, τ-muurolol, caryophyllene oxide, and methyleugenol as the most effective compounds against Staphylococcus aureus, considered as testing strain. Moreover, the microdilution method, assessed among a wide panel of microorganisms, revealed Listeria grayi and Staphylococcus aureus as the most sensitive among human tested strains and Clavibacter michiganensis among phytopathogens. GC-MS chemical profile showed that bioactive molecules represented only a small quantity of the whole EO: germacrene D (23.16%), β-caryophyllene (15.53%), δ-cadinene (5.50%), α-copaene (5.08%), and α-phellandrene (3.48%) were the main compounds, highlighting an uncommon composition among the genus Hedyosmum. Finally, H. sprucei EO was checked for cytotoxic potential against A549 (lung cancer) and MCF-7 (breast cancer) cell lines showing promising cytotoxic effects against both cell lines after 48 h (IC50 A549 = 44.05 ± 2.35 µg/mL; IC50 MCF-7 = 32.76 ± 4.92 µg/mL) and 72 h (IC50 A549 = 43.55 ± 2.80 µg/mL; IC50 MCF-7 = 33.64 ± 0.43 µg/mL).

The chemical composition, antifungal, antioxidant and cytotoxic activities of the essential oils (EOs) of mint (Mentha suaveolens), thyme (Coridothymus capitatus), oregano (Origanum hirtum) and rosemary (Rosmarinus officinalis) were investigated. The antifungal properties of the EOs were investigated against four species of Candida by a microdilution method. Cytotoxicity was tested on human keratinocyte (HaCaT) and lung cancer (A549) cell lines using the MTT test. DPPH· and ABTS·+ spectrophotometric assays and DPPH·-ABTS·+(HP)TLC-bioautographic assays were used to evaluate the antioxidant activity. The main compounds of thyme and oregano EOs were carvacrol and thymol, respectively; piperitenone oxide and γ-terpinene were the most abundant compounds of mint and rosemary EOs, respectively. All EOs showed activity against all Candida species in a range between 760 ± 290 to 3120 ± 0.0 µg/mL. Among the EOs, that of M. suaveolens showed a stronger cytotoxic activity on HaCaT cells. Thyme, oregano and rosemary EOs exhibited important antioxidant activities by ABTS ·+ assay compared with trolox.

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