## 1 Introduction
From this perspective, it may be important to explore the chemical variability of oregano EO composition and to understand the influence of this variability on its biological activities. One of the main sources of chemical variability in oregano EO is related to the genetic background of the plant. From this point of view, the species _Origanum vulgare_, native to and widespread in the Mediterranean region [18], encompasses many subspecies and hybrids, among which is the subspecies _Origanum heracleoticium_ [PERSON]. [PERSON] [19], which is one of the most common growing in Sicily [20]. Information is available on the phytochemistry of this subspecies [20; 21], but the biological activities of its EOs have not yet been investigated. On the contrary, no studies to the best of our knowledge have been conducted both on the chemical and biological features of the hybrid _Origanum vulgare ssp. viridulum_\(\times\)_Origanum vulgare ssp. hirthum_, introduced into cultivation in Sicily in the last decade. A lot of investigations have explored the intraspecific variability of the chemical composition of EOs from _Origanum vulgare_ species, while a remarkable variation has also been observed within each subspecies, bearing to noticeable differences in the chemical profile and, possibly, in the associated biological properties [20; 22]. Beyond genetic factors, this variability may also be due to environmental factors, such as, among others, geographical position [23] and altitude [24]. Regarding the chemical characterization of oregano EOs, very few data are available on the enantiomeric distribution of their main chiral compounds [25], even though this information may be useful not only for chemotaxonical characterization, but also for authenticity issues. Changes in enantiomeric distribution could also influence the biological activities of oregano EO [26]. In the present study, a detailed characterization of the chemical composition and biological activities of EOs obtained from plants of the subspecies _Origanum heracleoticum_ L. and the hybrid _Origanum vulgar ssp. viridulum_\(\times\)_Origanum vulgar ssp. hirthum_ is provided. The chemical characterization, besides their basic chemical profile, also included the determination of the enantiomeric distribution of chiral compounds present in their EOs and in their dried leaves and flowers. The study of their biological activities focused on antimicrobial, intestinal permeability and anti-inflammatory properties. To evaluate antimicrobial properties, different pathogen indicator strains were used, while the intestinal barrier integrity, reduction in pathogen adhesion and anti-inflammatory activity were evaluated in a widely used in vitro model of intestinal cells, the human Caco-2 cell line, differentiated on permeable filters. These conditions allowed for the reproduction of the environment of the intestinal mucosa, in which the epithelium separates the lumen from the inner body. A preliminary characterization carried out in our laboratory highlighted that the hybrid _Origanum vulgar ssp. viridulum_\(\times\)_Origanum vulgar ssp. hirthum_ was distinguished by a high content of carvacrol as the main EO constituent, thus allowing for a description of its EO as the carvacrol chemotype, whereas EOs from the subspecies _Origanum heracleoticum_ L. are known to belong to the thymol chemotype [20]. Thus, the aim of the present study was to provide detailed information on the chemical and biological properties of the EOs from these two genotypes to promote alternative and innovative applications in food and pharmaceutical products suited to their specific properties. In addition, the information collected may contribute to a deeper understanding of the influence of varying chemical profiles, such as those with carvacrol or thymol as predominant constituents, on the biological activities of oregano EOs.