Abstract

The aim of this study was to demonstrate the influence of the genotype on the inhibition of glycogen phosphorylase a (GPa), activity carried out by ethanolic extracts (EETs) obtained from Ugni molinae (Myrtaceae) leaves. Methodology: GPa (85 ng) activity was measured in the direction of glycogen synthesis by the release of phosphate from glucose-1-phosphate at 22 °C in 100 mL of buffer containing 50 mM Hepes (pH 7.2), 100 mM KCl, 2.5 mM EGTA, 2.5 mM MgCl2, 0.5 mM glucose-1-phosphate, and 1 mg/mL glycogen. Phosphate will be measured at 620 nm, 20 min after the addition of 150 mL of 1 M HCl containing 10 mg/mL ammonium molybdate and 0.38 mg/mL malachite green. The significance of the results was determined by Tukey test. The results show that there are significant differences at the fifty inhibitory concentrations (IC50) of the GPa between leaves of different genotype. Of the ten genotypes evaluated, the EET of the 19-1 genotype showed the highest inhibitory effect on GPa (IC50 = 1.03 μg/mL). By contrast, the EET of 19-1 ha genotype had the lowest effect (IC50 = 3.53 μg/mL). Differences in the triterpenoids profile between genotypes could explain the results obtained.