*3.2. Monovarietal Olive Oil Phenolic Content*

This research focused on three of the main active constituents of olive polyphenols, i.e., tyrosol, hydroxy-tyrosol and oleacein (3,4-DHPEA-EDA), and on the TPC of monovarietal oils. In general, the concentration and the main trend of these compounds varied among the analyzed cultivars. For example, tyrosol content was higher in cultivar Tortiglione than in Dritta and Gentile dell'Aquila with no significant changes (*p* > 0.05) during ripening, while it significantly increased in Sardinian cultivars and in two of the Apulian genotypes, i.e., Bambina and Oliva Rossa. An opposite trend was observed in cultivar Cima di Melfi, that showed a significant drop in tyrosol content at complete maturity of drupes (Table 3; Figure 2A).

**Table 3.** Phenolic compounds and total phenolic content (TPC) detected in VOOs of all the analyzed cultivars from fruits at different ripening stages (T2 = turning drupes, T3 = almost dark drupes, T4 = fully dark drupes).



**Table 3.** *Cont.*

Data are means (*n* = 3) ± standard deviation. Different letters for each parameter and region indicate significant differences according to one-way ANOVA followed by Fisher's LSD post-hoc test (*p* = 0.05).

**Figure 2.** Trend of variation in some polyphenolic compound contents in VOOs of the analyzed genotypes, during three developmental stages of olive fruits (T2, T3, T4). (**A**) Tyrosol; (**B**) hydroxy-tyrosol; (**C**) oleacein (3,4-DHPEA-EDA); (**D**) total phenol content (TPC).

> Hydroxy-tyrosol concentration was the lowest among the three studied compounds, generally showing its highest amount in two time-points, that is at T2 and T4. Among all

the analyzed cultivars, two Sardinian cultivars (Semidana and Sivigliana) had the highest hydroxy-tyrosol content, with values of about 0.9 and 1.2 mg kg−<sup>1</sup> olive oil, respectively. In particular, in Sivigliana cultivar, this compound first decreased when drupes were in advanced stage of ripening (T3) and then significantly increased at the end of fruit maturation. An exception to this behavior was recorded for cultivars Oliva Rossa and Corsicana, whose hydroxy-tyrosol contents were slightly higher at T3 (Table 3; Figure 2B).

The concentration of oleacein generally decreased with maturity stage in all the considered cultivars, with the only exception of Cima di Melfi and Gentile dell'Aquila, that showed a more evident and significant increase in this compound in fully ripe fruits (Table 3; Figure 2C). Cultivars Dritta and Bambina were the genotypes with the lowest amount of 3,4-DHPEA-EDA in their oils. Bambina VOO was already known for its particular phenolic pattern, which shows a significant contribution of flavonoids and a lesser amount of secoiridoid derivatives [49].

Finally, changes in the total phenol content (TPC) were generally recorded in most of the cultivars. Indeed, the concentration of total phenols was almost constant during drupe maturation or slightly increasing at the last stage of fruit ripening (T4), except for the Abruzzo cultivar Tortiglione and the Apulian cultivar Oliva Rossa, that showed a drastic and significant drop in the total phenol content in comparison with the first stage of fruit ripening (T4 vs. T2) (Table 3; Figure 2D). Sardinian cultivars showed, on the other hand, a slight but significant decrease in TPC at the T4 sampling. Anyway, the oils obtained from these cultivars, together with oils derived from most of the Apulian genotypes, were the ones with the highest and most stable amount of total phenols during all stages of fruit ripening.
