Subcritical ethanol extraction of flavonoids from Moringa oleifera leaf and evaluation of antioxidant activity

- A large scale subcritical ethanol extraction was conducted to extract flavonoids.
- An optimal condition of extraction was proposed.
- The extraction process was energy-saving.
- The extracts showed strong antioxidant ability.
- HPLC-MS analysis was performed to identify the flavonoids.

A large-scale process to extract flavonoids from Moringa oleifera leaf by subcritical ethanol was developed and HPLC-MS analysis was conducted to qualitatively identify the compounds in the extracts. To optimize the effects of process parameters on the yield of flavonoids, a Box-Behnken design combined with response surface methodology was conducted in the present work. The results indicated that the highest extraction yield of flavonoids by subcritical ethanol extraction could reach 2.60% using 70% ethanol at 126.6 °C for 2.05 h extraction. Under the optimized conditions, flavonoids yield was substantially improved by 26.7% compared with the traditional ethanol reflux method while the extraction time was only 2 h, and obvious energy saving was observed. FRAP and DPPH assays showed that the extracts had strong antioxidant and free radical scavenging activities.