Nelumbo nucifera leaves protect hydrogen peroxide-induced hepatic damage via antioxidant enzymes and HO-1/Nrf2 activation

Abstract

Naturally occurring phenolic compounds are widely found in plants. Here, the phenolic composition and hepatoprotective effect of the butanolic extract (BE) from Nelumbo nucifera leaves against H₂O₂-induced hepatic damage in cultured hepatocytes were investigated. BE showed high total phenol and flavonoid contents, and major phenolic compounds are quercetin, catechin, ferulic acid, rutin, and protocatechuic acid by HPLC analysis. BE effectively scavenged 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis(3-ethylbenzthiazoline)-6-sulfonic acid (ABTS) cation radicals (IC₅₀ values of 5.21 μg mL⁻¹ for DPPH and 6.22 μg mL⁻¹ for ABTS⁺) and showed strong reducing power. Pretreatment of BE prior to 650 μM H₂O₂ exposure markedly increased cell viability and suppressed H₂O₂-induced intracellular reactive oxygen species generation and AAPH-induced cell membrane lipid peroxidation. In addition, BE up-regulated intracellular glutathione levels under normal and oxidative stress conditions. Notably, the hepatoprotective effect of BE was directly correlated with the increased expression of superoxide dismutase-1 (SOD-1) by 0.62-fold, catalase (CAT) by 0.42-fold, and heme oxygenase-1 (HO-1) by 2.4-fold. Pretreatment of BE also increased the nuclear accumulation of Nrf2 by 8.1-fold indicating that increased SOD-1, CAT, and HO-1 expressions are Nrf2-mediated.