Bioactivity and phenolic composition from natural fermented table olives

Abstract

In the present work, the phenolic composition, and antioxidant and antimicrobial properties of twenty-four samples of naturally fermented table olives from the northeast of Portugal were evaluated. The analysis of phenolic composition was performed by HPLC/DAD, and ten compounds were identified, hydroxytyrosol, verbascoside derivate and hydroxytyrosol glycol being the most abundant. Total phenolic content varied between 2.37 and 64.17 μg mg⁻¹ of extract. The IC₅₀ values from the antioxidant activity methods tested varied between 0.30 and 1.66 mg mL⁻¹ for reducing power, and between 0.13 and 0.83 mg mL⁻¹ for DPPH. The results obtained in the antioxidant activity were extremely significantly correlated with the main phenolic compounds as well as with the total phenolic content. A principal component analysis allowed grouping the samples according to their phenolic composition and antioxidant potential. Table olive extracts were able to inhibit some pathogenic microorganisms, mainly Gram-positive bacteria. Higher antimicrobial inhibition was recorded in the extracts rich in phenolic compounds and higher antioxidant potential.