Microwave-assisted extraction (MAE) conditions using polynomial design for improving antioxidant phytochemicals in Berberis asiatica Roxb. ex DC. leaves

Microwave-assisted extraction condition is of great importance for increasing recovery of phytochemicals with lesser time and solvent consumption. In this regard, the advanced microwave extraction technique was applied for the first time for improving polyphenolic antioxidants in Berberis asiatica leaves using polynomial design. A combination of first and second order polynomial designs was used at different levels using Plackett-Burman and Box-Behnken design and a total of 29 experiments were conducted for determination of optimal extraction condition for polyphenolics. Under optimal extraction condition [microwave power - 500 W, sample to solvent ratio - 1:45 (g/ml) and methanol concentration - 60%], total phenolics (132.63 mg GAE/g), total flavonoids (31.36 mg QE/g), total tannins (145.17 mg TAE/g), ABTS (34.46 mM AAE/g), FRAP (708.07 mM AAE/g) and DPPH (34.12 mM AAE/g) antioxidant activities was recorded near close with predicted values. The extract also showed DNA and erythrocyte damage protective activity and reveals the presence of 12 phenolic compounds during high-performance liquid chromatography among which 4 compounds were reported first time from this species. Chlorogenic acid and catechin were found in higher concentration as compared with other phenolic compounds. The present study provides the potential of harnessing maximum antioxidant phytochemicals from the Berberis asiatica leaves using microwave-assisted extraction condition.