Abstract:

This paper reports the results obtained for the ultrasonic-assisted extraction and antioxidant activity in vitro of
flavonoids from fresh okras. The extraction process was optimized using response surface methodology. The evaluation of
antioxidant activity was carried out by reducing power, hydroxyl, superoxide anion and DPPH radical scavenging assays
in comparison to VC. The optimum extraction conditions were determined as 250 W, 1:25 (g/mL), 21 min, 75 ℃ and
50% for ultrasonic power, solid-to-solvent ratio, extraction time, temperature and ethanol concentration, respectively. The
experimentally observed yield of flavonoids under the optimized conditions was 4.85% on average, which approximated
the predicted value of 4.88%, showing the reliability of the optimized process. In hydroxyl, superoxide anion and DPPH
radical scavenging assays, the IC50 of the flavonoids extracted from okra were 6.00, 3.28 and 2.98 mg/mL, and the maximum
scavenging rates were 31.49%, 64.40% and 62.22%, respectively. Moreover, strong reducing power was observed. These
results support strong antioxidant activity in vitro for okra flavonoids.

Key words: okra, flavonoids, ultrasound-assisted extraction, response surface methodology, antioxidant activity