Natalija Bulaš, Klara Kraljić, Elda Vitanović, Maja Jukić Špika
Abstract
β-glucosidase plays a central role in the metabolism of the olive fruit by hydrolyzing secoiridoid glucosides and releasing aglycones, which strongly influence the phenolic profile of olives and thus also the virgin olive oil. These phenolic compounds, especially aglycones, are highly valued for their antioxidant, anti-inflammatory and general health-promoting properties, as well as for their contribution to the sensory quality and oxidative stability of virgin olive oil. However, the activity of β-glucosidase can be affected by external factors, including fungicides used in olive cultivation. Copper-based fungicides are still widely used and effective for disease control, but their intensive use has raised concerns about environmental impact and food quality. One possible consequence of copper accumulation in olive tissue is the interaction with endogenous enzymes that influence the formation of phenolic compounds. Understanding how copper ions affect β-glucosidase activity is therefore crucial for assessing their broader effects on olive fruit metabolism..
This study investigated the inhibitory effects of different copper salts at a range of concentrations on β-glucosidase activity. Enzyme activity was determined using p-nitrophenyl-β-D-glucopyranoside as a substrate, allowing for quantitative assessment of inhibition. Results revealed a clear concentration- dependent inhibition of β-glucosidase activity by copper salts. Increasing copper concentrations consistently led to stronger inhibition of the enzyme, confirming that copper ions directly interfere with the catalytic mechanism. IC50 estimations suggest that the extent of inhibition depends not only on concentration but also on the chemical form of copper.
These results emphasize the need to better understand the role of copper in olive cultivation, as its impact on β-glucosidase activity may ultimately shape the phenolic composition of virgin olive oil. Such knowledge can guide the reduction of copper inputs and support the transition towards more sustainable plant protection practices.
