Impact of ultrasound pretreatment with different solvents on the antioxidant activity, phenolic and flavonoid compounds of the St. John’s wort (Hypericum perforatum L.) extract

In this study, the effect of ultrasound pretreatment (at 40 kW power, for 20 min) with single partial solvent including water and ethanol and two partial solvents containing water/ethanol in the form of 30% (water): 70% (ethanol) and 60% (water): 40% (ethanol), were considered on the extraction efficiency, total phenolic and flavonoid compounds, as well as the free radical inhibition rate of the St. John’s wort (Hypericum perforatum L.) extract. In order to analyze the data, a completely randomized design was used in three replications, and the comparison of means was done by Duncan's multi-range test, at the probability level of α=1%, and using SPSS 14. Based on the results, the highest amount of extraction efficiency (18.3 %), total phenolic (0.295 mg GAE/g dw) and flavonoid (0.105 mg QE/g dw) compounds and the inhibition rate of free radicals (84.21 %) was measured in the samples pre-treated with ultrasound along with two partial solvents [30% (water): 70% (ethanol)] and the lowest amount of extraction efficiency (4.21%), total phenolic (0.051mg GAE/g dw) and flavonoid (0.0115 mg QE/g dw) compounds as well as free radical inhibition rate (47.53 %) was specified in water (100 %) solvent.