Photoprotective Agents Obtained from Aromatic Plants Grown in Colombia: Total Phenolic Content, Antioxidant Activity, and Assessment of Cytotoxic Potential in Cancer Cell Lines of Cymbopogon flexuosus L. and Tagetes lucida Cav. Essential Oils

Photoprotective agents obtained from plants provide benefits for the health of the skin. The present study aims to assess the total phenolic content (TPC) and in vitro UV-protective properties of twelve essential oils (EOs) from plants grown in Colombia and to evaluate the antioxidant and cytotoxic potential of two species identified as photoprotective potentials: Cymbopogon flexuosus and Tagetes lucida. The composition of EOs was studied by GC/MS. The cytotoxicity of both EOs was examined using an MTT assay, and an H2-DCFDA probe was employed to estimate the intracellular production of ROS in HepG2 and Calu-1 cells. Major constituents (≥10%) were neral, geranial, geranyl acetate in C. flexuosus and estragole in T. lucida. The TPC for C. flexuosus and T. lucida EOs were ≥10 mg GAE/g of byproduct. Both EOs showed photoprotective properties (SPFin vitro: 13−14), and long-wavelength UVA protection (λc > 370 nm). HepG2 and Calu-1 cells exposed to C. flexuosus exhibited antiproliferative activity (˂50%) at 125 µg/mL, while T. lucida was at 250 and 500 µg/mL. The IC50 values for C. flexuosus were 75 and 100 µg/mL in HepG2 and Calu-1 cells, respectively, whereas those for T. lucida were >250 µg/mL. These EOs achieved significant inhibitory effects (between 15.6 and 40.4%) against H2O2-induced oxidative stress. The results showed that EO compounds recognized as antioxidants could counteract the effects elicited by H2O2.

Chemical Composition, Antibacterial and Anti-Quorum Sensing Activities of Pimenta dioica L. Essential Oil and Its Major Compound (Eugenol) against Foodborne Pathogenic Bacteria

The Pimenta dioica essential oil and its main compound (eugenol) were tested for their antibacterial potency against eight Gram-negative and Gram-positive bacteria implicated in food intoxication. This essential oil and its main component were evaluated for their ability in inhibiting Quorum sensing (QS)-dependent mechanisms such as motility in Pseudomonas aeruginosa PAO1, production of violacein by Chromobacterium violaceum and biofilm formation on stainless steel and glass surfaces. Our results demonstrated that P. dioica essential oil and eugenol were active against all tested strains with a maximum of inhibition against Listeria monocytogenes CECT 933 (26.66 ± 0.57 mm). The minimal inhibitory concentration (MIC) value of the tested essential oil and eugenol was about 0.048 mg/mL for all strains. The obtained results demonstrated that 4CMI eugenol inhibited foodborne strains biofilm formation on the glass strips by 73.79% and by 75.90% on polystyrene. Moreover, 0.048 mg/mL (MIC) of P. dioica essential oil inhibited the violacein production by 69.30%. At 100 µg/mL, P. dioica oil and eugenol affected the motility of PAO1 by 42.00% and 29.17%, respectively. Low concentrations of P. dioica essential oil are active against the quorum sensing phenomena and biofilm potency. Thus, this essential oil could be further investigated for new molecules useful for the treatment of toxi-alimentary infections.

Essential Oils of Aromatic Plants with Antibacterial, Anti-Biofilm and Anti-Quorum Sensing Activities against Pathogenic Bacteria

Both the ability of bacteria to form biofilms and communicate through quorum sensing allows them to develop different survival or virulence traits that lead to increased bacterial resistance against conventional antibiotic therapy. Here, seventeen essential oils (EOs) were investigated for the antimicrobial, antibiofilm, and anti-quorum sensing activities on Escherichia. coli O157:H7, Escherichia coli O33, and Staphylococcus epidermidis ATCC 12228. All essential oils were isolated from plant material by using hydrodistillation and analyzed by GC-MS. The antimicrobial activity was performed by using the microdilution technique. Subinhibitory concentrations of each EO were assayed for biofilm inhibition in both bacterial strains. Quantification of violacein in Chromobacterium violaceum CV026 was performed for the anti-quorum sensing activity. The cytotoxicity activity of the EOs was evaluated on Vero cell line by using MTT method. Thymol-carvacrol-chemotype (I and II) oils from Lippia origanoides and Thymus vulgaris oil exhibited the higher antimicrobial activity with MIC values of 0.37-0.75 mg/mL. In addition, these EOs strongly inhibited the biofilm formation and violacein (QS) production in a concentration-dependent manner, highlighting thymol-carvacrol-chemotype (II) oil as the best candidate for further studies in antibiotic design and development against bacterial resistance.