The involvement of phenolic-rich extracts from Galician autochthonous extra-virgin olive oils against the α-glucosidase and α-amylase inhibition

Abstract

‘Brava’ and ‘Mansa de Figueiredo’ extra-virgin olive oils (EVOOs) are two varieties identified from north-western Spain. A systematic phenolic characterization of the studied oils was undertaken by LC-ESI-IT-MS. In addition, the role of dietary polyphenols from these EVOOs has been evaluated against the inhibition of key enzymes (α-glucosidase and α-amylase) in the management of diabetes mellitus (DM). Oleuropein and ligstroside derivatives comprised 83% and 67% of the total phenolic compounds in ‘Brava’ and ‘Mansa de Figueiredo’ EVOOs, respectively. The main secoiridoids from oleuropein were DOA (3,4-DHPEA-EDA, 59 and 22 mg kg−1, respectively) and the main isomer of OlAgl (3,4-DHPEA-EA, 74 and 23 mg kg−1). The main secoiridoids from ligstroside were D-LigAgl (p-HPEA-EDA or oleocanthal, 23 and 167 mg kg−1) and the main isomer of LigAgl (p-HPEA-EA, 214 and 114 mg kg−1). For α-glucosidase, both EVOO extracts displayed stronger inhibitory activity (IC50 values of 60 ± 8 and 118 ± 9 μg mL−1, respectively) than the commercial inhibitor acarbose (IC50 = 356 ± 21 μg mL−1). Nevertheless, for α-amylase, only ‘Brava’ extracts showed anti-α-amylase capacity. A daily VOO intake lower than the requirements of EFSA seem to be enough to reach both 50% for α-glucosidase and 25% for α-amylase inhibition. These findings support the potential health benefits derived from Galician EVOOs that might be probably linked to the outstanding high concentration levels of phenolic acids and flavonoids.