This study was carried out to characterize the chemical composition of the essential oils from seven Eucalyptus species (E. griffithsii, E. hemiphloia, E. lesouefii, E. longicornis, E. pyriformis, E. viminalis, and E. wandoo), as well as their phytotoxic and antibacterial activities. The essential oils were analyzed by GC/MS and the potential in vitro phytotoxicity was evaluated against germination and radical elongation of Raphanus sativus, Lolium multiflorum, and Sinapis arvensis seeds. The antibiofilm activity was studied against both Gram-negative (Pseudomonas aeruginosa, Escherichia coli and Acinetobacter baumannii) and Gram-positive (Staphylococcus aureus and Listeria monocytogenes) bacteria. The inhibition of biofilm formation and its metabolism was determined at different times. Eucalyptol was the most abundant component in all essential oils studied (ranging from 40.8% for E. lesouefii EO to 73.6% for E. wandoo) except for that of E. pyriformis where it was present but at 15.1%. E. pyriformis was the most active against both germination and radical elongation of S. arvensis. The action of all essential oils proved to be highly effective in inhibiting the bacterial adhesion process of the five strains considered. In light of these results, these essential oils could have potential applications both in the agricultural and health fields.

The Eucalyptus genus (Myrtaceae) is characterized by a richness in essential oils (EO) with multiple biological activities. This study reports the chemical composition and the phytotoxic and antimicrobial activities of the EOs from Tunisian E.occidentalis, E.striaticalyx and E.stricklandii. The EOs were analyzed using GC/MS and their phytotoxicities were assessed against the germination and seedling growth of Sinapis arvensis, Trifolium campestre and Lolium rigidum. Antimicrobial activity was investigated against both Gram-negative (Pseudomonas aeruginosa, Escherichia coli and Acinetobacter baumannii) and Gram-positive (Staphylococcus aureus and Listeria monocytogenes) bacteria. The inhibition of biofilm formation and its metabolism was determined at different times. All EOs were rich in oxygenated monoterpenes (36.3–84.8%); the EO of E.occidentalis was rich in sesquiterpenes, both oxygenated and hydrocarbon (40.0% and 15.0%, respectively). Eucalyptol was the main constituent in all samples. The EOs showed phytotoxic activity on seed germination and seedling growth, depending both on chemical composition and weed. The EOs show a remarkable antibacterial potential resulting in a significant inhibition of the formation of bacterial biofilm and its metabolism, depending on the EO and the strain, with activity on the mature biofilm as well. Therefore, these Eucalyptus EOs could have potential applications both in the food and health fields.

Eucalyptus species are characterized by their richness in essential oils (EOs) with a great diversity of biological activities. This study reports the chemical composition and the phytotoxic and antibiofilm activities of the EOs of six Eucalyptus species growing in Tunisia: E. bicostata, E. gigantea, E. intertexta, E. obliqua, E. pauciflora and E. tereticornis. Four EOs were rich above all in oxygenated monoterpenes (25.3–91.4%), with eucalyptol as the main constituent. However, in the EOs of E. pauciflora and E. tereticornis, sesquiterpene hydrocarbons (28.8–54.0%) were the main class of constituents; piperitone was the main constituent of both EOs. The phytotoxicity of the EOs was tested against germination and radicle elongation of the weeds Sinapis arvensis and Lolium multiflorum and the crop Raphanus sativus, resulting in the different inhibition of seed germination and radicle elongation depending on both chemical composition and the seed tested, with remarkable phytotoxicity towards S. arvensis and R. sativus. Furthermore, almost all EOs showed antibacterial potential, resulting in significant inhibition of bacterial biofilm formation and the metabolism of Gram-positive (Staphylococcus aureus subsp. aureus and Listeria monocytogenes) and Gram-negative (Acinetobacter baumannii, Pseudomonas aeruginosa and Escherichia coli) bacterial strains, in addition to acting on mature biofilms. The EOs were inhibitory against all bacterial strains tested and usually reluctant to undergo the action of conventional antibiotics. Therefore, these EOs may be considered for applications both as herbicides and in food and health fields.

Anethum graveolens L. has been known as an aromatic, medicinal, and culinary herb since ancient times. The main purpose of this study was to determine the chemical composition, antibacterial, antibiofilm, and anti-quorum sensing activities of the essential oil (EO) obtained by hydro-distillation of the aerial parts. Twelve components were identified, representing 92.55% of the analyzed essential oil. Limonene (48.05%), carvone (37.94%), cis-dihydrocarvone (3.5%), and trans-carvone (1.07%) were the main identified constituents. Results showed that the obtained EO was effective against eight bacterial strains at different degrees. Concerning the antibiofilm activity, limonene was more effective against biofilm formation than the essential oil when tested using sub-inhibitory concentrations. The results of anti-swarming activity tested against P. aeruginosa PAO1 revealed that A. graveolens induced more potent inhibitory effects in the swarming behavior of the PAO1 strain when compared to limonene, with a percentage reaching 33.33% at a concentration of 100 µg/mL. The ADME profiling of the identified phytocompounds confirms their important pharmacokinetic and drug-like properties. The in-silico study using molecular docking approaches reveals a high binding score between the identified compounds and known target enzymes involved in antibacterial and anti-quorum sensing (QS) activities. Overall, the obtained results highlight the possible use of A. graveolens EO to prevent food contamination with foodborne pathogenic bacteria.

The complex taxonomy of Eucalyptus genus, the renewed interest in natural compounds able to combat microbial strains, the overuse of synthetic pesticides, the consequent request for alternative control methods were the reasons for this research. The essential oils (Eos) of Eucalyptus bosistoana, Eucalyptus melliodora, Eucalyptus odorata, Eucalyptus paniculata, Eucalyptus salmonopholia, and Eucalyptus transcontinentalis were analyzed by GC/MS and their potential phytotoxic activity was evaluated against the germination and radicle elongation of Sinapis arvensis, Raphanus sativus and Lolium multiflorum. The antibiofilm activity was assayed against both Gram-positive (Staphylococcus aureus and Listeria monocytogenes) and Gram-negative (Pseudomonas aeruginosa, Escherichia coli, and Acinetobacter baumannii) bacteria. Monoterpenoids were the most representative constituents in all EOs and eucalyptol was the dominant component except in E. melliodora EO, in which p-cymene was the most abundant. In phytotoxic assays, the EOs from E. odorata and E. paniculata were the most active against germination and radical elongation of the tested seeds. Finally, the Eucalyptus EOs proved their capacity to effectively inhibit the adhesion process of all five pathogen strains, with percentages often reaching and exceeding 90%. These Eucalytpus EOs could have possible employments in the food, health and agricultural fields.

The cultivation of different species of Eucalyptus has recently expanded in Liguria (Italy) due to the growing demand of the North European floricultural market. Eucalyptus tree branches are cut and selected for their quality, resulting in large amounts of waste biomass to be disposed of. The aim of our study was to evaluate the phytotoxic and antimicrobial activities of essential oils (EOs) from pruning wastes of E. cinerea (EC) and E. nicholii (EN), for potential applications in agriculture. Phytochemical analyses showed eucalyptol (1,8-cineole) as the major component in both EOs, but the EO yield of EN was higher than that of EC, in agreement with a significantly higher oil gland density on EN leaves. EOs from both species showed phytotoxicity on both weeds tested, but no significant inhibition on horticultural crop seed germination, except for Raphanus sativus. The EO from EC showed the strongest antibacterial activity, while the EO from EN showed the strongest antifungal activity. Concluding, EOs from Eucalyptus pruning may be used as possible alternatives to synthetic herbicides and pesticides, acting as antimicrobial and antifungal agents, thus representing a safe strategy for crop management programs.

In this work, we aimed to study the chemical composition of the essential oils from bulbs and leaves of two cultivars of Allium sativum L. and two of A. ampeloprasum L. var. holmense. Moreover, we investigated their activity against four common bacterial strains responsible for food contamination (Listeria monocytogenes, Escherichia coli, Acinetobacter baumannii, and Staphylococcus aureus) by formation of biofilms. The susceptibility of bacterial biofilms was evaluated by crystal violet assay, whereas the metabolic changes occurring in the bacterial cells were ascertained through the MTT test. The essential oils were characterized by the presence of most characteristic components, although with different composition between the species and the cultivars. The essential oils inhibited the capacity of the pathogenic bacteria to form biofilms (up to 79.85 against L. monocytogenes) and/or acted on their cell metabolism (with inhibition of 68.57% and 68.89% against L. monocytogenes and S. aureus, respectively). The capacity of the essential oils to act against these foodborne bacteria could suggests further ideas for industrial applications and confirms the versatility of these essential oils as food preservatives.

This work aimed to evaluate the chemical composition of the essential oils (EOs) of two cultivars of Allium sativum and their antibiofilm activity against the food pathogens Acinetobacter baumannii, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus. The crystal violet assay ascertained the susceptibility of the bacterial biofilms, while the MTT assay let to evaluations of the metabolic changes occurring in the bacterial cells within biofilms. Their chemical composition indicated some sulfuric compounds (i.e., allicin, diallyl disulfide, and allyl propyl disulfide), and decene as some of the main components of the EOs. The aerial parts and bulbs’ EOs from the two cultivars showed chemical differences, which seemed to affect the antibiofilm activity. The EOs from aerial parts of ‘Bianco del Veneto’ inhibited the biofilm formation of L. monocytogenes and E. coli (60.55% and 40.33%, respectively). In comparison, the ‘Staravec’ EO inhibited the cellular metabolism of E. coli (62.44%) and S. aureus (51.52%) sessile cells. These results indicate their possible use as preserving agents in the food industry and suggest their potential exploitation in the development of new formulations to avoid or limit nosocomial infections.