# The Infestation of Olive Fruits by _Bactrocera oleae_ ([PERSON])
## 2 Results and Discussion
### Effect of Bactrocera oleae Infestation on the Phenolic Profile of VOO
On the contrary, the secoiridoid derivatives containing tyrosol suffered only slight decreases or even notable increases as in the case of _p_-HPEA-EA in cvs. Picual and Manzanilla. Interestingly, [PERSON] et al. [38] also reported that compounds derived from tyrosol, such as _p_-HPEA-EA, increased their content in cv. Istrska belica oils proportionally to the severity of the infestation. On the contrary, we previously found in _V. dahliae_-infected Picual olives that the average content of both the tyrosol and the hydroxytyrosol derivatives were around 20% lower than in the control oils [25]. As previously mentioned in Section 2.1 in relation to the different effect of the pathogenic fungus and _B. oleae_, the differences observed in terms of phenolic compounds could also be explained by the existence of different defense systems against both biotic stressor, pathogen, and pest. In order to explore the connection between VOO phenolics and _B. oleae_ infestation, Pearson's correlation coefficients were computed using the phenolic data of the oils from the three olive cultivars (Table S4). Significant negative correlation coefficients (_p_\(\leq\) 0.05) were found for most phenolic compounds. Thus, content of acetoxypinoresinol showed the highest negative correlation coefficient with the fruit infestation (r = \(-\)0.91), followed by tyrosol and hydroxytyrosol. The content of 3,4-DHPEA-EA displayed the highest coefficient among the secoiridoid compounds (r = \(-\)0.69). PCA analysis was applied to the same subset of phenolic compounds with statistically significant correlation coefficients (Table S3). The first and second principal components described 89% of the total variability (PC1 61.89% and PC2 27.29%). The PCA bi-plot shows the great influence of BO infestation on the phenolic profile of VOO (Figure 4). All control oils were clearly segregated and located in the left part of the plot (Figure 4B). The oils from cv. Hojibalca were located in the upper quadrant, associated to the flavones lutein and apigenin, which are more abundant in this olive cultivar. The oils from cvs. Picual and Manzanilla, having a quite similar phenolic distribution, were located in the lower left quadrant, associated to _p_-HPEA-EA and 3,4-DHPEA-EA (Figure 4A). Despite the obvious cultivar differences reflected in the left part of the quadrant, after the fly attack, the oils show very similar phenolic profiles that do not segregate the different cultivars, as shown in the right part of the plot (Figure 4B). As mentioned in the introductory section, it is generally accepted that the content of phenolic glucosides in olive fruit is the main factor determining the phenolic content of VOO. Accordingly, the lower phenolic content found in the oils of fruits infested by _B. oleate_ could be due to a lower phenolic content in these fruits. However, the analysis of secoiridoid glucosides of the three olive cultivars in this study did not show significant differences between the two groups. Figure 4: Principal component analysis of the main phenolic components of oils from non-infested (C) and infested (I) olive fruits (Picual, Manzanilla, and Hoijblanca). (**A**) vector distribution of the phenolic compounds. (**B**) distribution of cultivars-infestation status. differences between the phenolic content of healthy and infested Picual and Hojiblanca fruits, and even a significantly higher oleuropein and ligstroside contents were found in _B. oleae_-infested Manzanilla fruits compared to healthy fruits of the same cultivar (Table S5). The fact that the phenolic profiles of the fruits were not affected by the infestation but the content of phenolic compounds of the oils were drastically reduced suggests that _B. oleae_ infestation could alter the status of the hydrolytic and oxidative enzymatic activities acting during the olive oil extraction process.