Abstract
Mediterranean diet health benefits have been partially attributed to the dietary consumption of extra virgin olive oil (VOO). Most recent interest has focused on the biologically active phenolic compounds naturally present in VOO. Selected VOO from Italy were investigated for their phenolic profile and inhibitory activity against α-glucosidase and α-amylase, as well as angiotensin-converting enzyme (ACE). These enzymes have been linked to hyperglycemia-associated to hypertension. The total phenolic content (Folin-Ciocalteu) ranged from 109 to 250mg/kg of oil and was well correlated with the high-performance liquid chromatography (HPLC) data (r2=0.8533). The phenolic profile obtained by HPLC revealed the presence of 3,4-dihydroxyphenylethanol (3,4-DHPEA; 2.9±2mg/kg) and p-hydroxyphenylethanol (p-HPEA; 2.6±1.3mg/kg), as the main phenolic alcohols. Secoiridoids and their derivatives were also detected in high concentration in all samples, particularly 3,4-DHPEA-EDA (55±38mg/kg) and p-HPEA-EDA (42±14mg/kg). Vanillic acid (1.8±1.1mg/kg), vanillin (1.2±0.5mg/kg), p-coumaric acid (0.94±0.7mg/kg), apigenin (1.0±0.2mg/kg) and luteolin (2.4±0.5) were also identified. All samples demonstrated a stronger activity against α-glucosidase with respect to α-amylase. The sample that was richer in phenolics showed a half maximal inhibitory concentration of 184 and 258μg/mL against α-glucosidase and α-amylase, respectively. The same sample exhibited the highest activity against the ACE. In conclusion this in vitro study evidenced the hypoglycemic and ACE inhibitory activities of VOOs phenolic extracts. The multivariate statistical model pointed out that the effect of secoiridoids was more pronounced than flavonoids. PRACTICAL APPLICATIONS: In this study potential health benefits of extra virgin olive oil micronutrients (phenolic compounds) were confirmed through assays for the two major carbohydrate digestive enzymes, α-glucosidase and α-amylase as well as for the angiotensin I-converting enzyme. These enzymes have been linked to hyperglycemia-associated to hypertension that is a common condition especially in a late diabetic stage. The in vitro inhibitory activities that were encountered for these enzymes provide a strong biochemical rationale for further in vivo studies and dietary management strategy for patients affected by diabetes type 2 and/or hypertension. © 2011 Wiley Periodicals, Inc.