Effect of harvest on the agronomic, mineral and antioxidant profile of three oregano species (<i>Origanum onites</i> L., <i>Origanum vulgare</i> L. ssp. <i>hirtum</i>, and <i>Origanum acutidens</i> (Hand.-Mazz.) Ietswaart)

This study primarily aims to examine the variations in plant characteristics, micro- and macronutrient levels, heavy metal content, and antioxidant properties (2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)), along with antioxidant compounds such as phenolics and flavonoids, across different oregano species cultivated under identical ecological conditions. <i>Origanum vulgare</i> demonstrated the highest fresh (292.25 g/plant) and dry herbage yield (153.34 g/plant). The antioxidant activity varied significantly depending on the oregano species and harvest time. <i>Origanum acutidens</i> showed the highest DPPH radical scavenging activity during the early flowering stage. Conversely, <i>Origanum onites</i> L. displayed the lowest antioxidant activities, as measured by DPPH assay, during the same developmental phase. <i>O. vulgare</i> exhibited the strongest ABTS activity (0.997 mg TE/g dry weight (DW)) in the early flowering stage. Antioxidant activity in <i>O. onites</i> tended to decrease from pre-flowering to full flowering across all assays. Total phenolic content followed a similar trend, with <i>O. vulgare</i> reaching a maximum value at early flowering. Total flavonoid content was highest in <i>O. acutidens</i> during later development stages. The most abundant macronutrients, based on their average values of different harvest times, were calcium (Ca), potassium (K), magnesium (Mg), and phosphorus (P), respectively. The micro, macronutrient, and heavy metal content varied significantly between oregano species and across harvest periods within the same species. Heavy metal levels in oregano samples generally fell below WHO safety limits, except for cobalt (Co) and Chromium (Cr). Multivariate statistical techniques, including principal component analysis (PCA) and correlation analysis, were utilized to elucidate the interrelationships among oregano species, plant characteristics, antioxidant capacity, and mineral composition, thereby providing a comprehensive assessment of the factors governing oregano's qualitative and nutritional characteristics. These findings emphasize the critical role of oregano species and harvest timing in determining plant growth, antioxidant characteristics, and nutritional properties.