Microwave-assisted extraction of antioxidant compounds from sunflower hulls

The objective was to determine the adequate conditions for the microwave-assisted extraction of antioxidant compounds from the seed hull of sunflower hybrids. The existence of genetic and environmental variability in the phenolic content obtained under the selected extraction conditions was also analyzed. The extractions were carried out at 70 °C-20 and 90 °C-10 min, using water as solvent and a power of 600 W. The total phenol, flavonoid and antioxidant activity were evaluated. The microwave extraction process at 90 °C-10 min gave significantly higher values of total phenol (407.13 ± 6.11–512.71 ± 23.54 mg gallic acid⋅100 g−1 hull), flavonoids (210.09 ± 6.15–297.64 ± 5.68 mg catechin⋅100 g−1 hull) and antioxidant activity (76.73 ± 4.40–110.80 ± 3.51 μmol TE⋅g−1 hull) than those obtained at 70 °C-20 min. The cultivation environment also significantly affected the antioxidant yield, with total phenol and flavonoid contents being significantly higher for the hybrids grown in Balcarce than for those from Tandil. A significant interaction between hybrids and cultivation environmental was also observed for the antioxidant activity, indicating that the environmental effects were not similar among hybrids. The results of this study provide valuable information related to giving added value to a residue of the oil industry.