3.1.2. Antioxidant Activity

The chelating activity percentages obtained using two different methods, are also shown in Table 2. ABTS + radical cation assay and the DPPH free radical scavenging method were used. The capacity of P, HYT-L and RA to scavenge the ABTS + radical was higher than 80%, while the chelating activity of HYT-F, NOVS, and NOS was of 79.62%, 70.61% and 70.17%, respectively. On the other hand, scavenging ability of P was also the highest by measuring the stability of the DPPH radical, 92.55%. The chelating activity of HYT-L, NOVS, NOS, RA, and HYT-F ranged from 89% to 78%. Thus, the extracts with greatest chelating capacity were those obtained from pomegranate, hydroxytyrosol and rosemary, which is related with their high content of phenols, such as, punicalagin, hydroxytyrosol and rosmarinic compounds (carnosic acid, carnosol, and rosmarinic acid), respectively.

**Table 2.** Total phenolic content (TPC) of natural extracts (mg GAE/g) and their antioxidant activity by measuring their ABTS, and DPPH radical scavenging activity, together to their ORACHP, and FRAP (μM TE/g).


GAE: Gallic acid equivalents; SD: Standard deviation; Superscript letters indicate significant differences (*p* < 0.05) between natural extracts. P: Pomegranate extract, RA: Rosemary extract rich in Rosmarinic Acid; NOS: Rosemary extract rich in diterpenes; NOVS: Rosemary extract rich in diterpenes and with lecitin as emulsifier; HYT-L: Hydroxytyrosol extract obtained from olive leaf; HYT-F: Hydroxytyrosol extract obtained from olive fruit.

The hydrophilic antioxidant capacity of the natural extracts obtained by measuring the oxygen radical absorbance is shown in Table 2. However, in this case, the extract with the greatest antioxidant activity was HYT-L (147.46 μM TE/g), followed by P (146.39 μM TE/g), HYT-F (140.54 μM TE/g), RA (123.2 μM TE/g), NOVS (49.16 μM TE/g) and NOS (45.18 μM TE/g). As it can be appreciated, a grea<sup>t</sup> significant difference (*p* < 0.05) exists among rosmarinic extracts (NOS and NOVS) rich in diterpenes (carnosic acid and carnosol) and RA rich in rosmarinic acid, together with P, HYT-L and HYT-F. This fact could be explained by lipophilic activity of NOS and NOVS, because of this measurement is carried out in a hydrophilic system. In this way, the rest of extracts are watersoluble, as P, as well as HYT-L, HYT-F and RA present dual affinities, both to polar and non-polar solvents.

The efficiency of the natural plant extracts to reduce Fe+++ to Fe++ as a antioxidant power measured is also presented in Table 2 expressed in μM Trolox Equivalents (TE)/g. Obtained data showed as that all the extracts have a good and similar ferric reducing antioxidant power, ranging from 73.8 μM TE/g (RA) to 61.3 μM TE/g (P). The order of antioxidant activity using this method was RA > NOVS > HYT-F > HYT-L > NOS > P. All the extracts had high levels of reducing power, which indicated the presence of some compounds that are electron donors and could react with free radicals to convert them into more stable products.
