Volatile and non-volatile phenolics as quality determinants of oregano (Origanum sp.) cultivated in the temperate zone of Central Europe

Plants rich in phenolics are known for their remarkable biological activity, especially antimicrobial and antioxidant activities. Among them, the genus Origanum (Lamiaceae) has gained particular attention because of its interesting chemical composition, reflected in a dominance of phenolics in the volatile and non‐volatile fractions. The volatile fraction (essential oil) is characterized by a significant content of phenolic monoterpens (carvacrol, thymol), as well asnon-volatiles like phenolic acids (i.a. rosmarinic, lithospermic acids) and flavonoids. In accordance with such chemical compositions, Origanum plants demonstrate various activities, and are widely used in the pharmaceutical industry, as a food preservative and flavouring, and most importantly, as a culinary herb. This altogether leads to the significant economic importance of Origanum species, gathered under the common name ‘oregano’. However, Origanum taxonomy is highly complex, e.g., O.vulgare includes six subspecies, each chemically polymorphic, especially in essential oil composition and rosmarinic acid content. Among them, O. vulgare ssp. hirtum is considered the most valuable due to its pure carvacrol chemotype. Nevertheless, many varieties, landraces, and forms are available for stakeholders. The subtle morphological differences between Origanum taxa often lead to misidentification, which is problematic since each subspecies is typically associated with a distinct chemotype that determines its biological activity. Such confusion may result in incorrect assessments regarding the properties and standardization of oregano raw materials. So far, oregano cultivations have been located mainly within warmer climates. However, due to global warming, these plants may also be cultivated in the temperate zone of Central Europe. In this study, selected Origanum species and subspecies (O. vulgare ssp. hirtum, O. vulgare ssp. virens, and O. syriacum) grown in Poland were evaluated for their morphological and chemical characteristics. Particular emphasis was placed on essential oil and phenolic acid profiles, with carvacrol and rosmarinic acid contents as key quality markers, determined by GC-MS and HPLC.