Quality characteristics and antioxidant activity of onion peel extracts by extraction methods

Abstract

This study was conducted to evaluate the antioxidant activities and the quality characteristics of 70% ethanol extracts from onion peels with different extraction methods (autoclave extraction, AE; low temperature high pressure extraction, LTPE; reflux extraction, RE; and stirrer extraction, SE). The yields of AE, LTPE, RE and SE were 9.00%, 5.39%, 13.21% and 12.41%, respectively. The total polyphenol and flavonoid contents in the AE were significantly higher than in the other extracts. The DPPH radical scavenging abilities with a concentration of 100 mg% (w/v) were : AE, 28.9%; RE, 26.07%; LTPE, 24.35%; and SE, 19.53%. The ABTS radical scavenging ability and the nitrite scavenging activity showed the same tendency as that of the DPPH radical scavenging ability. The angiotensin –converting enzyme (ACE) inhibitory activities of the LTPE and AE were higher than those of the RE and SE. The α-Glucosidase inhibitory activity of the RE was higher than that of the extracts with other extraction methods. The nitrite scavenging activities with a concentration of 10 mg/mL were: AE. 33.97%; RE, 35.47%; LTPE, 21.86%; and SE, 21.71%. The ferrous ion chelating activity of the LTPE (54.73%) was significantly higher than that of the other extracts. These results suggest that AE is the superior method for the enhancement of anti-oxidant activity, and onion peel can be used as a natural antioxidant material for health foods and can be a good ingredient of functional foods.

Antioxidant and Immune Stimulating Effects of Allium cepa Skin in the RAW 264.7 Cells and in the C57BL/6 Mouse Immunosuppressed by Cyclophosphamide

“…OS extract in DPPH radical scavenging activity showed significant increase in a dose dependent manner. Previous research reported that DPPH radical scavenging activity of OS ethanolic extract was 28.39% at 1 mg/mL [ 27 ], while it was 46.89% at the same concentration in our study. OS extracts produced by ethanol, hot water, and subcritical water showed the different DPPH radical scavenging activities with 72.25%, 49.68%, and 64.72%, respectively [ 22 ].…”

“…ABTS radical scavenging activity of OS increased in a dose-dependent manner. ABTS radical scavenging activity of OS ethanolic extraction was 33.29% in 1 mg/mL [ 27 ]. The high contents of total polyphenol in Indian OS cultivars showed the high antioxidant activities in DPPH and ABTS assays [ 13 ].…”