Inhibitory activity of phenolic compounds from Extra Virgin Olive Oils on the enzymes involved in diabetes, obesity and hypertension

Mediterranean diet health benefits have been partially attributed to thedietary consumption of extra virgin olive oil (VOO). Most recent interest hasfocused on the biologically active phenolic compounds naturally present inVOO. Selected VOO from Italy were investigated for their phenolic profileand inhibitory activity against a-glucosidase and a-amylase, as well asangiotensin-converting enzyme (ACE). These enzymes have been linked tohyperglycemia-associated to hypertension. The total phenolic content(Folin-Ciocalteu) ranged from 109 to 250 mg/kg of oil and was wellcorrelated with the high-performance liquid chromatography (HPLC)data (r2 = 0.8533). The phenolic profile obtained by HPLC revealed thepresence of 3,4-dihydroxyphenylethanol (3,4-DHPEA; 2.9 2 mg/kg) andp-hydroxyphenylethanol (p-HPEA; 2.6 1.3 mg/kg), as the main phenolicalcohols. Secoiridoids and their derivatives were also detected in high concentrationin all samples, particularly 3,4-DHPEA-EDA (55 38 mg/kg)and p-HPEA-EDA (42 14 mg/kg). Vanillic acid (1.8 1.1 mg/kg), vanillin(1.2 0.5 mg/kg), p-coumaric acid (0.94 0.7 mg/kg), apigenin(1.0 0.2 mg/kg) and luteolin (2.4 0.5) were also identified. All samplesdemonstrated a stronger activity against a-glucosidase with respect toa-amylase. The sample that was richer in phenolics showed a half maximal inhibitory concentration of 184 and 258 mg/mL against a-glucosidase anda-amylase, respectively. The same sample exhibited the highest activityagainst the ACE. In conclusion this in vitro study evidenced the hypoglycemicand ACE inhibitory activities of VOOs phenolic extracts. The multivariatestatistical model pointed out that the effect of secoiridoids was morepronounced than flavonoids.