Determination of Bioactive Potential in a Semi-domesticated Population of Oregano (Lippia graveolens Kunth) with Organic Fertilization

Mexican oregano (Lippia graveolens Kunth) is an aromatic species of high culinary and medicinal relevance. In Mexico, more than 40 taxa with characteristic aroma and flavor are commercially recognized as oregano, with L. graveolens being the most widely distributed and economically important. Despite its relevance, few domesticated or semi-domesticated cultivars exist, and wild populations remain the main source of raw material, raising concerns regarding sustainability and quality standardization. The essential oil and oleoresins of L. graveolens possess recognized bioactivity, including antioxidant, antifungal, antibacterial, and anti-inflammatory properties, largely attributed to phenolic compounds such as thymol and carvacrol. Given the increasing global demand for natural bioactives and functional foods, optimizing cultivation practices is essential to enhance both the yield and phytochemical quality of this species. This study evaluated the effect of organic fertilization (0, 5, 10, and 15 t ha⁻¹ of vermicompost) on the phenolic profile, flavonoid content, and antioxidant capacity of oregano oleoresin obtained from a semi-domesticated population across three harvests. The highest phenolic concentration (≈500 mg GAE g⁻¹ extract) and greatest antioxidant activity (ABTS > 3.5 × 10⁵ µmol TE g⁻¹ extract) were observed at the 5 t ha⁻¹ dose during the second harvest. Flavonoid content peaked in the third harvest (480–620 mg QE g⁻¹ extract), whereas the unfertilized control exhibited the highest DPPH activity in the first harvest. Overall, the results indicate that vermicompost dosage and harvest timing substantially influence the functional quality of L. graveolens. Moderate organic fertilization, particularly 5 t ha⁻¹, enhances the biosynthesis of bioactive secondary metabolites, underscoring its potential for sustainable production systems.