Antioxidant Activity of Lotus Leaf Fractions with Different Polarities and the Effect of Acid Hydrolysis on the Effective Fraction
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Abstract:
The aim of this study was to identify and further improve the antioxidant activity of the effective fraction in lotus leaves. Lotus leaf fractions were prepared by systematic solvent extraction, and antioxidant activity was measured to identify the effective antioxidant fraction, which was then hydrolyzed by using hydrochloric acid. The results showed that among all fractions with different polarities, the low-polar fraction (ethyl acetate fraction) showed the strongest antioxidant activity in terms of percentage of hydroxyl radicals and superoxide anions scavenged and total antioxidant capacity. Therefore, this fraction was identified as the effective antioxidant fraction of lotus leaf. The antioxidant capacity of the effective fraction was significantly improved by hydrochloric acid hydrolysis (P < 0.05 or P < 0.001). Compared with the effective fraction before hydrolysis, the total reducing power, percentage of 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenged, ferric-reducing antioxidant power (FRAP, OD593), total antioxidant power (OD695nm), and percentage of hydroxyl radicals scavenged of the post-hydrolytic fraction showed an improvement by 48.5%, 58.22%, 64.3%, 22.15%, and 100.48%, respectively. The percentage of superoxide anion radicals scavenged showed an improvement from 42.43% ± 1.23% to 44.97% ± 0.22%. The results demonstrated that the active antioxidants of lotus leaf comprised of mainly low-polar compounds in the effective fraction (ethyl acetate fraction), and hydrochloric acid hydrolysis was an effective approach to improve the antioxidant capacity of this fraction. This study provides a basis for further research and development of functional foods by using lotus leaf.
