Beyond Thymol and Carvacrol: Characterizing the Phenolic Profiles and Antioxidant Capacity of Portuguese Oregano and Thyme for Food Applications

Oregano (Origanum vulgare L.) and thyme (Thymus mastichina L.) are popular aromatic plants used in the culinary sphere and are known for their antioxidant capacity. This study investigates the variability in the antioxidant capacity and phenolic profiles, focusing on flavonoids and phenolic acids, of oregano and thyme accessions from the Portuguese Bank of Plant Germplasm. The antioxidant capacity was assessed by measurements using the ferric-ion-reducing antioxidant power and DPPH radical scavenging activity assays, Total Phenolic Content, and individual phenolic compounds. Oregano extracts presented the highest total phenolic content (~2152 mg GAE/g DW), while thyme extracts showed the highest ferric-reducing antioxidant powers. However, both aromatic plants (~0.58 mmol TE/g DW) presented similar DPPH radical scavenging capacities. Rosmarinic acid was the major phenolic compound in methanolic extracts from oregano and thyme, but higher amounts were found in thyme (23.11 to 40.45 mg/g DW). The accessions of oregano and thyme showed statistical differences in the phenolic content and antioxidant capacity. This study provides valuable insights into the phenolic profile of Portuguese oregano and thyme, which could constitute potential sources of natural antioxidants and bioactive compounds, to be used by the food industry as natural food additives.