The impact of temperature and ultrasound on the polyphenols extraction and antioxidant activity of Mozafati, Sayer, and Kabkab date byproduct varieties

In this study, the effect of ultrasound and temperature at three different levels—30, 50, and 70 °C on the amount of phenolic compounds and antioxidant properties of the extract obtained from the byproducts of three date byproducts—Kabkab, Mozafati, and Sayer were evaluated. In order to conduct a comprehensive assessment of antioxidant activities, three methods including DPPH and H2O2 radical scavenging activities, and ion chelating ability were employed. The Pierson analysis was used to examine the correlation between polyphenolic compounds and antioxidant activities. According to the results, the use of ultrasound treatment enhanced the amount of extracted polyphenols and flavonoids in all date varieties. Furthermore, the polyphenol and flavonoid contents were found to increase up to 50°C during extraction, but subsequently decreased. The highest amount of polyphenols and flavonoids was achieved using the ultrasound treatment in 50° C in Sayer variety, 4.64 ± 0.07 mg Gallic acid/g and 0.326 ± 0.0112 mg quercetin/g, respectively. DPPH and H2O2 radical scavenging activities were increased after ultrasound treatment at 50°C but then decreased (P<0.05). Maximum H2O2 scavenging activity was observed in Mozafati variety. The iron chelating ability decreased after extraction with ultrasound treatment at 30° C and then increased significantly (P<0.05) until reached the maximum amount of 40.433 ± 0.802% in Sayer variety. Results showed a strong correlation between polyphenols and flavonoids with antioxidant activities. Therefore, the antioxidant properties of the tested date byproducts are likely to derive from their polyphenolic content, making them an economical source of these bioactive compounds.