Synergistic Effect of Cloves (Syzygium aromaticum), Thyme (Thymus vulgaris) and Lemon (Citrus limon) Blended Essential Oils Optimized by Mixture Design for Improving the Antioxidant Activity

Background: Combining various essential oils (EOs) for developing pharmaceutical formulations has been the focus of attention in recent years. Objectives: This study aimed to determine the antioxidant effect of the combination of three Eos obtained from clove (Syzygium aromaticum L.), lemon peel (Citrus limon L.), and thyme (Thymus vulgaris L.) by using mixture design. Methods: The EOs of lemon peel (EOL), clove (EOC), and thyme (EOT) as well as their combination were analyzed using a gas chromatograph with flame ionization detector (GC/FID). The antioxidant activities of the EOs from EOL, EOC, and EOT as well as their combination were measured adopting DPPH assay. The construction and statistical analysis of the experiment were designed using the NemrodW (LPRAI, version 2000) software. Results: EOL, EOC, and EOT were found capable of neutralizing DPPH radical. EOC was distinguished by its strongest antiradical activity with IC50=15.02±0.02 µg/mL. EOT had an IC50=29.20±0.12 µg/mL while EOL had 188.69±0.95 µg/mL. The positive standard BHT was detected to be IC50=24±0.02 µg/ mL. The optimal, combinative mixture of essential oils may have been determined based on these isoresponse curves which allowed fixing the ideal combinations of ingredient in terms of quantity to obtain an EO mixture possessing appreciable and optimal antioxidant characteristics. The predicted antioxidant properties determined by the mixing plan model were retained and the experiments were carried out respecting the contents of proposed ingredients of 25.7% EOT, 32.3% EOL, and 41.9% EOC equivalent to 15.42 mg, 19.38 mg and 25.14 mg, respectively. This resulted in arriving at an essential oil mixture with an experimental IC50=11.023±0.145 µg/mL which was similar to those of the predicted antioxidant properties with an order of 10.907±0.212 µg/mL and a non-significant difference of P<0.05, based on which the validity of the proposed mixing plan model was determined. The combined EO was also found to be rich in eugenol (32.35±1.13%), thymol (25.49±0.03%), and limonene (21.30±0.02%). Conclusion: Statistical planning and the development of utility profiles for mixtures of essential oils may have been used to predict the optimal composition as well as to determine their antioxidant profile

A comparative assessment of antifungal activity of essential oils of five medicinal plants from Tunisia

The leaf essential oil yields of clementine, cypress, rosemary, tea, and thyme were 0.22, 0.87, 1.46, 1.20, and 0.72%, respectively, based on the dry weight of the plant material. The leaf essential oils of rosemary, tea, and thyme contained the highest levels of oxygenated monoterpenes (60.14-91.70%). Rosemary and tea leaf essential oils were rich in 1,8-cineole (49.98% and 57.55%, respectively), and they have potent antifungal activity against Alternaria alternata strain (MIC = 5000 μg/ml). Thyme was rich in carvacrol (78.54%) and had a MIC of 6000 μg/ml against A. alternata strain. Clementine leaf essential oil was characterized by the predominance of monoterpene hydrocarbons (88.65%), and it possessed a weak antifungal activity against A. alternata (MIC = 8000 μg/ml). Cypress leaf essential oil was characterized by the predominance of oxygenated sesquiterpenes (60.67%), having an antifungal activity of 8000 μg/ml

Effect of Emulsifiers and Wall Materials on Particle Size Distribution and Stability of the Blended Essential Oils Nanoemulsions

In the present work, microencapsulation of the essential oil blend (thyme + clove + lemon peel) was successfully used to produce a product that can be used as food additives or in the pharmaceutical industry for the manufacture of a food supplement or so-called nutraceutical of plant origin. The characterization of the powder of the microcapsules made it possible to observe that the essential oil was incorporated successfully into the coating matrix designed by the wall material which is maltodextrin and which represented a barrier allowing the protection of the active principle as well as the controlling its release and retaining the properties of the encapsulated essential oil for a long time. This powder of microcapsules of mixture of essential oils can also be used successfully for medical purposes in capsules in order to remedy certain pathology, in particular for its antioxidant, antibacterial and anti-inflammatory properties. &nbsp

Phenological stage effect on phenolic composition and repellent potential of Mentha pulegium against Tribolium castaneum and Lasioderma serricorne

Objective: To elucidate for the first time the phenological stage effect on polyphenol, flavonoid and proanthocyanidin contents of pennyroyal (Mentha pulegium) as well as their antioxidant capacities and insecticidal potentials against Tribolium castaneum and Lasioderma serricorne. Methods: Crude methanol extracts from pennyroyal (Mentha pulegium) aerial parts were evaluated for their antiradical, reducing power activities and repellent potentials against selected coleopteran insects during different phenological stages. Results: Phenolic contents of pennyroyal aerial parts and their antioxidant effects were significantly dependent on maturity stage of the plant. The maximum of phenol production was reached during the full flowering stage. Apigenin was the major phenol in Mentha pulegium with an amount of 6.01 mg/g of dry vegetable matter during this period. Nevertheless, at fructification stage, the highest antioxidant activity was not related to high phenolic content. The repulsive effect of pennyroyal extract showed that Lasioderma serricorne was more susceptible to pennyroyal extract than Tribolium castaneum with corresponding median repellent dose values of 0.124 and 0.006 mg/mL respectively. Moreover, great differences in insect repulsion depending on extract concentrations, exposure time and developmental stage was observed. For the lowest concentration (0.125 mg/mL), the repellent effect against Tribolium reached its maximum (90%) during the fructification stage (after 24 h of exposure) while this repellent effect was 80% during the vegetative stage. Conclusions: Due to the strong insecticidal potential of pennyroyal extracts, this study highlights the therapeutic properties of this plant and encourages its use as a safer, environmental-friendly and efficient insecticide in food industry