Antioxidant and Cytoprotective Effects of Lotus (Nelumbo nucifera) Leaves Phenolic Fraction

Abstract

Phenolic rich ethyl acetate fraction (EAF) from lotus leaves was prepared and its bioactive components, antioxidant and cytoprotective effects were investigated. EAF showed high total phenolic content and flavonoid content and contained rutin (11,331.3±4.5 mg/100 g EAF), catechin (10,853.8±5.8 mg/100 g EAF), sinapic acid (1,961.3±5.6 mg/100 g EAF), chlorogenic acid (631.9±2.3 mg/100 g EAF), syringic acid (512.3±2.5 mg/100 g EAF), and quercetin (415.0±2.1 mg/100 g EAF). EAF exerted the IC50 of 4.46 μg/mL and 5.35 μg/mL toward DPPH and ABTS cation radicals, respectively, and showed strong reducing power, which was better than that of ascorbic acid, a positive control. Additionally, EAF protected hydroxyl radical-induced DNA damage indicated by the conversion of supercoiled pBR322 plasmid DNA to the open circular form and inhibited lipid peroxidation of polyunsaturated fatty acid in a linoleic acid emulsion. In cultured hepatocytes, EAF exerted a cytoprotective effect against oxidative stress by inhibiting intracellular reactive oxygen species formation and membrane lipid peroxidation. In addition, depletion of glutathione under oxidative stress was remarkably restored by treatment with EAF. The results suggest that EAF have great potential to be used against oxidative stress-induced health conditions.

Keywords: DNA damage; antioxidant; cytoprotection; lotus leaf.

Fig. 1

Electrophoretic pattern of pBR322 DNA in the presence of EAF (A), and the protection effect of EAF on hydroxyl radical-induced DNA damage (B). The bars with different letters (a–d) represent significant differences (P<0.05). Values are expressed as means±SD (n=3).

Fig. 2

Lipid peroxidation inhibition activity of EAF in a linoleic acid emulsion. The bars with different (a–d) letters represent significant differences (P<0.05). Values are expressed as means±SD (n=3).

Fig. 3

Effects of EAF on cytoprotection (A), intracellular ROS formation (B), membrane lipid peroxidation (C), and GSH level (D) in the cultured human hepatocytes under oxidative stress. The bars with different (a–d) letters represent significant differences (P<0.05). Values are expressed as means±SD (n=3).