## 3 Results and Discussion
### Influence on VOOs Quality and Composition
#### 3.2.5 Phenolic Compounds and Antioxidant Capacity  
Table 7 shows the profile of phenolic compounds in VOOs obtained from olive fruits harvested from rainfed olive trees and irrigated at different watering regimes. Coratina oils, produced from the olive fruits harvested in 2019 and in 2020 from the trees grown on the ameliorate karst soil in Croatia, were characterized by very high concentrations of phenolic compounds (more than 1000 mg/kg). In both years of our study, watering regimes applied did not significantly affect the concentration of total phenolic compounds (TPC) determined as well as the concentration of seciridoids. The lack of difference between T\({}_{3}\) (100% EtC treatment) and deficit irrigation treatments (T\({}_{1}\), T\({}_{2}\)) in TPC indicated that similar content could be achieved with less demand in the water supply. [PERSON] et al. [49] also did not find differences in TPC or phenolic profiles between oil from rainfed treatment and oil from waste water irrigated treatments (20 and 40% ETc) of Chemlali olive trees grown in Tunisia. However, [PERSON] et al. [45] found different effects of irrigation in two consecutive years: in one-year an increased water value during irrigation decreased the TPC value, while in the second year of investigation there were no significant differences found among rainfed, RDI, 100% and 125% ETc treatments for TPC levels. The effect of irrigation on TPC in oil could depend on irrigation levels but also on the specific cultivar [45; 47]. Nevertheless, the reduction of TPC levels was mostly reported in irrigated treatments compared to the rainfed conditions [9; 15; 54; 55]. [PERSON] et al. [47] reported that oils from Frantoio cv. olive trees with a higher water status showed a lower concentration of phenolic compounds. Higher concentration of phenolic content in rainfed oil samples could be due to plant stress responses and defence mechanisms due to severe conditions involving water deficit [9]. Water deficit could activate the phenylalanine ammonia lyase (PAL) enzyme involved in the polyphenols biosynthetic pathway, which could be one of the reasons for the increase in concentration of some particular polyphenols in olive oils in response to water stress during drought [9; 46]. In both years of our investigation, there were no severe drought conditions in September, just before fruit harvesting (Figure 1) and that is probably one of the reasons for no significant difference among watering treatments in TPC and secoridoids. The rain event prior to harvesting increases the fruit water content, which reduce dissolution of phenolic compounds in the oil and have marked impact on olive oil phenolic content [18]. Regarding the concentration of secoridoids, contradictory data can be found in the literature. [PERSON] et al. [9] have found a slight increase in some important secoridoids (ligstrostride aglycon) in olive oil after irrigation, compared with oils obtained from rainfed Chemlali trees. On the contrary, most authors [15; 16; 56] have found that the level of secoridoids diminished as the water level during irrigation increased. [PERSON] et al. [15] reported the highest level of secoridoids in rainfed olive oils in two consecutive crop seasons. Conversely, the concentration of simple phenols increased in all irrigated treatments, especially in the T\({}_{3}\) treatment, due to increased concentration of hydroxytyrosol and tyrosol (Table 7). However, [PERSON] et al. [9] reported that these phenolic alcohols were negatively affected by the irrigation of Chemlali olive trees in Tunisia. [PERSON] et al. [16] found that concentrations of tyrosol were similar for all irrigation treatments (full, deficit, complementary) in Frantoio olive oil, while changes of hydroxytyrosol due to irrigation regimes applied were not the same in each of three years of investigation. Phenolic acids decreased in treatments with irrigation in 2019, especially in T\({}_{3}\), while in 2020 that decrease was not significant (Table 7). [PERSON] et al.