# Effect of Selected _Trichoderma_ Strains and Metabolites on Olive Drupes
## 4 Discussion
In downstream data analysis steps, fragment ions are matched with precursor ions based on mass and retention time [63]. In this study, an untargeted metabolomic approach was used to evaluate phenolic profiles for olive drupes. The analysis of chromatograms led to the putative identification of 13 differentially accumulated compounds among all treatments. Oleeuropein (the main secoriidoid) and luteolin (the main flavonoid) concentration increased in treated samples compared to control. Metabolomic profiles of olive drupes following the application of M10, KV906, T22, and metabolite HA were grouped separately. This result may indicate that the olive plants have a similar response when inoculated with _Trichoderma_ fungi and treated with their metabolites [51]. However, the identified differential metabolites were not always common to all treatments (Figure 1). The targeted metabolomics method estimated the effects of each biological treatment on the phenolic' levels in the olive's drupes. Four more representative phenolic classes (flavonoids, secoriidoids, simple phenols, and oleosides) were considered. Following the treatments, an increase in the oleeuropein's content and a decrease in the oleeuropein's precursors (11-methyl ester and ligstroside) concentrations were determined, demonstrating the ability of _Trichoderma_ and its metabolites to interact with the enzyme \(\beta\)-glucosidase [64] responsible for this biotransformation (Figure 5) [65]. About flavonoids, an improvement of the flavone luteolin's level (except in olive drupes obtained from plants treated by T22) and a decrease in the flavonoid rutin's concentration (except in olive drupes obtained from plants treated by 6 PP) were observed in all tested samples (Table 4), indicating the ability of the treatments (except T22 and 6 PP) to affect principally the flavone synthase activity rather than flavonol synthase (Figure 6). Finally, the levels' variation of oleuropein and luteolin in olive drupes after the bio-treatment was studied in detail. Oleeuropein and luteolin were used as indicators of the secoriidoids and flavonoids variation, respectively. Oleeuropein acts in _Olea europaea_ as signaling molecule to protect the plant against UV-B radiation [67]. It has beneficial properties on human health, preventing cancer, cardiovascular diseases, inflammatory and oxidant damage [68]. Luteolin avoids oxidative and inflammatory processes with important implications for preventing neurodegenerative, cancer, and cardiovascular diseases and fortifying the immune system [69, 70]. All _Trichoderma_ spores and metabolites treatments affected the secoriidoid oleuropein and flavonoid luteolin levels (in some cases,they were less abundant in treated plants) and generally influenced the flavonoids more than secoriridoids production. The biological treatment (6 PP, GV41, and T22) improved the deuropein content, while the luteolin levels were higher after 6 PP, GV41, M10, HA, and KV906 treatments confirming a different interaction capacity of the bioteatments with the enzymes involved in the two biosynthetic pathways. Figure 5: Oleuropein biosynthesis. Figure 6: Flavonoid’s biosynthesis [66].