## 3 Results and Discussion  
### Antioxidant Capacity  
#### 3.1.1 Oregon  
All methanolic extracts from \(O\). _vulgare_ showed an antioxidant capacity (Table 3). The samples presented a similar scavenging ability in both the DPPH radical assay and FRAP assay, ranging between 0.4476 and 0.6029 mmol TE/g DW and 1354.86 and 1932.33 umol Fe\({}^{2+}\)/g DW, respectively. Likewise, the oregano extracts showed comparable phenolic contents, ranging between 1639.71 mg GAE/g DW for BPGV10423 and 2660.86 mg GAE/g DW for BPGV11408. This similarity between samples could indicate that, despite the different locations and consequently different climatic conditions, the high antioxidant potential of oregano is ensured. Only two samples of oregano were statistically different. Oregano BPGV11408, collected in Santarem, showed the highest TPC and the highest antioxidant capacity, with a significant difference (\(p<0.05\)), while the oregano from Portalegre (BPGV10423) showed a significantly lower TPC and lower ferric reducing antioxidant power (\(p<0.05\)). These results could be related to temperature, since Santarem was the location with the highest average temperature during the months of April to June, showing that the oregano may have increased the production of the phenolic content as a response to heat-induced stress, since these compounds are involved in the defense mechanism towards different abiotic stresses [21; 22]. Also, Portalegre and Braganga were the districts with a lower rainfall volume during this period and correspond to the samples with a lower antioxidant capacity in FRAP and DPPH radical assays (BPVG10423 and BPVG11267). This may indicate that oregano under drought stress decreases the content of phenolic compounds. These findings are similar to those reported by [PERSON] et al. [22], which concluded that water stressed plants decrease the concentration of phenolics and antioxidant activity assessed by the DPPH radical assay.  
Considering BPGV10442, the multiplication of the original BPGV10442 did not influence the antioxidant capacity or TPC of the oregano extract (\(p>0.05\)).  
Compared with other studies, our oregano samples showed the highest TPC. For example, [PERSON] et al. [23] reported a lower amount of TPC (ranging from 20.3 to 35.5 mg GAE/g DW) in seven accessions of oregano belonging to three subspecies (_virens, vulgare_, and _gracile_) collected in Iran. A higher TPC was found by [PERSON] et al. [24] (ranging from 79.5 mg to 147 mg GAE/g DW) in 42 accessions of _O. vulgare_ from Germany National GeneBank, but below our TPC. More recently, on a Greek Island, the oregano collected by [PERSON] et al. [25] showed a higher TPC (362.1 mg GAE/g DW) using Ultrasound-Assisted Extraction, but it was not comparable to our results due to a different extraction method. These unrelated results may suggest that several factors, such as extraction methods, environmental parameters, and post-harvesting conditions, may affect plant metabolism and, consequently, the expression of phenolic compounds [26; 27].  
Previously, [PERSON] et al. [28] reported a lower antioxidant capacity of _O. virens_ from Madeira Island (0.0011 mmol TE/g DW by a DPPH radical assay). This might be related to the use of \(n\)-hexane as the extraction solvent and the use of activated carbon to remove chlorophylls, which might have co-extracted other compounds with antioxidant activity.