Total phenol content and antioxidant activity of water solutions of plant extracts

Water solutions of extracts were investigated for total phenol content, flavonoid content and antioxidant activity. Susceptibility to degradation of water solutions of plant extracts, under light and in the dark, during storage at room temperature was investigated in order to determine their stability prior to their application for fortification of food products. Large dispersion of total phenol (TP) content in the investigated model solutions of selected extracts (olive leaves, green tea, red grape, red wine, pine bark PE 5:1, pine bark PE 95 %, resveratrol), ranging from 11.10 mg GAE/100 mL to 92.19 mg GAE/100 mL was observed. Consequently, large dispersion of total flavonoids (TF) content (8.89 mg to 61.75 mg CTE/100 mL) was also observed. Since phenols have been mostly responsible for antioxidant activity of extracts, in most cases, antioxidant activity followed the TP content. That was proven by estimation of correlation coefficient between the total phenol content and antioxidant activity. Correlation coefficients between investigated parameters ranged from 0.5749 to 0.9604. During storage of 5 weeks at room temperature loss of phenols and flavonoids occurred. Antioxidant activity decreased with the decrease of TP and TF content. Degradations of phenols and flavonoids were more pronounced in samples stored at light.