Chenopodium ambrosioides (L.) is a medicinal and aromatic plant widely used in the Moroccan traditional medicine for its important pharmacological properties. In order to contribute to the valorization of this plant, the current study aimed at evaluating, for the first time, the variation in the yield, chemical composition, and insecticidal and phytotoxic activities of C. ambrosioides essential oil (CAEO) isolated from leaves and inflorescences. The results obtained showed that the CAEO yields vary significantly according to the distilled plant part, with 0.75 ± 0.15% for the leaves and 1.2 ± 0.34% for the inflorescences. CAEO profiling showed quantitative more than qualitative differences. Leaf CAEO was rich in δ-3-carene (61.51%), followed by p-cymene (14.67%) and 1,2:3,4-diepoxy-p-menthane (6.19%). However, inflorescence CAEO was dominated by the same compounds but with variable levels (δ-3-Carene: 44.29%; 1,2:3,4-diepoxy-p-menthane: 19.46%; and p-cymene: 17.85%). The CAEOs from the leaves and inflorescences showed a very interesting inhibiting effect on the germination and growth of the three species used, namely Medicago sativa, Linum rusitatissimum, and Raphanus sativus. However, there was no significant difference between these CAEOs. Similarly, for the insecticidal activity, CAEOs exhibited an important and similar toxicity against Tribolium confusum adults with LD₅₀ of 4.30 and 4.46 μL/L of air and LD₉₀ of 6.51 and 9.62 μL/L air for toxicity by fumigation, while values for contact toxicity on filter paper were 0.04 and 0.05 μL/cm² for LD₅₀ and 0.08 and 0.09 μL/cm² for LD₉₀.

Antimicrobial resistance is a growing global challenge, rendering many standard treatments ineffective. Essential oils (EOs) of cinnamon (Cinnamomum aromaticum Nees) and clove (Syzygium aromaticum (L.) Merr. et Perry) may offer an alternative solution due to their high antimicrobial properties and their abilities to fight resistant pathogens. This study evaluates the antimicrobial activity of these two EOs, and their synergistic potential when combined with two antibiotics (ciprofloxacin and vancomycin) and two antifungals (fluconazole and amphotericin B) against various bacterial and yeasts strains. The antimicrobial activities of each EO were evaluated by agar diffusion and broth microdilution assays, while the synergetic effects with antimicrobials were determined by calculating the fractional inhibitory concentration index (FICI) using the checkerboard method. The chemical composition of the EOs was analyzed using Gas Chromatography-Mass Spectrometry (GC-MS). The identification of individual components in the EOs was achieved by comparing their mass spectra with the NIST MS Search database and by correlating their retention times with those of known standards. GC-MS analysis revealed that the main constituents of S. aromaticum EO were eugenol (71.49%) and β-caryophyllene (23.43%), while C. aromaticum EO were dominated by cinnamaldehyde (47,04%) and cinnamyl acetate (18.93%). Antimicrobial activity showed that cinnamon EO exhibits highest effectiveness against all tested strains, with inhibition zones (IZ) ranging from 16.99 mm to 53.16 mm, and minimum inhibitory concentrations (MIC) and minimum microbicidal concentrations (MMC) ranging from 0.039 mg/mL to 0.156 mg/mL. However, for clove EO, the IZ ranged from 9.31 mm to 29.91 mm, with MIC and MMC values from 0.313 mg/mL to 1.25 mg/mL. In combination with antibiotics (ciprofloxacin and vancomycin), the studied EOs showed promising synergistic effects with reduction up to 128-fold. As regards antifungals (amphotericin B, and fluconazole), the synergistic effects were recorded with MIC gains up to 32-fold. Our findings demonstrate that the EOs from C. aromaticum and S. aromaticum exhibit significant broad-spectrum antimicrobial activity against diverse yeast and bacterial strains. This highlights their potential as bases for the development of novel plant-based antimicrobial agents. Importantly, the observed synergistic effects of these EOs with conventional antibiotics support their integration into medical treatments as a strategy to address microbial resistance. Future research should aim to elucidate the mechanisms underlying these synergistic actions, optimize their application, and enhance their therapeutic efficacy.

Lavandula is a genus of small herbs and sub-shrubs belongs to the Lamiaceae family, one of the most economically important plant families, which includes approximately 236 genera and nearly 7200 species. The Lavandula genus contains about 34 species widely distributed globally, mainly in the Mediterranean region, and used from ancient time to cure diverse diseases. The essential oils (EOs) obtained from species of this genus are widely used in perfumery, cosmetics, food processing, as well as in aromatherapy products due to their multiple biological properties. This chapter reports the traditional uses, chemical composition, and biological activities of EOs extracted from Lavandula species growing wild and/or cultivated in Morocco. The chemical composition of Moroccan Lavandula EOs is mainly composed of monoterpenes. The majority of EOs extracted from lavender are characterized by a high antimicrobial power, especially those with a richness in phenolic compounds, particularly carvacrol. Some species have been reported to have a very powerful anti-oxidant effect, while others have an important acaricidal or/and insecticidal activities.