Modeling phase separation and droplet size of W/O emulsions with oregano essential oil as a function of its formulation and homogenization conditions

Oregano Essential Oil Micro- and Nanoencapsulation With Bioactive Properties for Biotechnological and Biomedical Applications

Due to the preservative, antioxidant, antimicrobial, and therapeutic properties of oregano essential oil (OEO), it has received an emerging interest for biotechnological and biomedical applications. However, stability and bioactivity can be compromised by its natural volatile and hydrophobic nature, and by external factors including light, heat, or oxygen. Therefore, micro- and nanoencapsulation are being employed to guarantee oregano oil protection from outside aggressions and to maximize its potential. Oregano oil encapsulation is an interesting strategy used to increase its stability, enhance its bioactivity, and decrease its volatility. At the same time, the versatility that micro- and nanocarriers offer, allows to prepare tailored systems that can provide a controlled and targeted release of the encapsulated principle, influence its bioactive activities, or even provide additional properties. Most common materials used to prepare these carriers are based on lipids and cyclodextrins, due to their hydrophobic nature, polymers due to their versatility in composition, and hybrid lipid-polymer systems. In this context, recently developed micro- and nanocarriers encapsulating oregano oil with applications in the biotechnological and biomedical fields will be discussed.

Essential oils microemulsions prepared with high-frequency ultrasound: physical properties and antimicrobial activity

Essential oils (EOs) have demonstrated antimicrobial activity against bacteria due to the effects of their major components. The direct application of EOs may present a rapid volatilization of its components and can decrease their effectiveness. Encapsulation by means of emulsification can provide protection to lipid compounds on a microscale. The aim of this study was to characterize microemulsions of cinnamon essential oil (CEO), oregano essential oil (OEO), and rosemary essential oil (REO) prepared by high-frequency ultrasound and evaluate their antimicrobial activities against Escherichia coli and Listeria monocytogenes. The microemulsions (oil-in-water, O/W) of EOs were prepared using high-frequency ultrasound, applying a wave amplitude of 84 µm for 15 min (REO and CEO) or 30 min (OEO). The antimicrobial activity was determined by inoculating 10⁸ CFU/mL of bacteria. Nonsurvival of the bacteria was confirmed by plate count in tryptic soy agar, determining the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). The microemulsions exhibited droplet size diameters of 1.98 to 5.46 µm, showing high encapsulation efficiencies (79.91-81.97%) and low separation rates (2.50-6.67%). The MIC and MBC for the microemulsions for both bacteria were 20-75% less than values obtained for the non-encapsulated EOs. This study demonstrates that high-frequency ultrasound is a suitable technique for obtaining stable microemulsions to deliver natural antimicrobials that can be applied to control bacteria of high relevance in food safety.

New Tricks for Old Guys: Recent Developments in the Chemistry, Biochemistry, Applications and Exploitation of Selected Species from the Lamiaceae Family

Lamiaceae is one of the largest families of flowering plants comprising about 250 genera and over 7,000 species. Most of the plants of this family are aromatic and therefore important source of essential oils. Lamiaceae are widely used as culinary herbs and reported as medicinal plants in several folk traditions. In the Mediterranean area oregano, sage, rosemary, thyme and lavender stand out for geographical diffusion and variety of uses. The aim of this review is to provide recent data dealing with the phytochemical and pharmacological studies, and the more recent applications of the essential oils and the non-volatile phytocomplexes. This literature survey suggests how the deeper understanding of biomolecular processes in the health and food sectors as per as pest control bioremediation of cultural heritage, or interaction with human microbiome, fields, leads to the rediscovery and new potential applications of well-known plants.