Aim: The study was aimed to assess the ability of Borassus flabellifer haustorium methanolic extract (BHE) on de novo glutathione biosynthesis in normal and pro-oxidant exposed cells via Nuclear factor erythroid 2-related factor 2 (Nrf2) and haeme oxygenase-1 (HO1) signaling in 2,2'-Azobis(2-methylpropionamidine) di-hydrochloride (AAPH) induced cytotoxicity in normal intestinal epithelial cells (IEC-6 cells).
Methods: The in vitro antioxidant activity was determined in terms of radical scavenging and ex vivo hemolysis. The cytoprotective effect was studied using AAP H as the alkoxyl radical inducer in IEC-6 cell model. The mechanistic basis of protection is determined by Nrf2/HO1 expression using qPCR.
Results: In vitro screening observed DPPH, hydrogen peroxide and ABTS radical scavenging activity for the BHE; further, BHE also protected the oxidative hemolysis in the erythrocytes induced by AAPH. In IEC-6 cells, AAPH treatment significantly reduced the cell viability (p < 0.001) by inducing lipid peroxidation. Further, there observed a significant reduction in the activities of enzymes involved in the de novo glutathione biosynthesis (p < 0.01) and glutathione reductase in these cells. However, pretreatment with BHE (10, 25 and 50 µg/mL) dose-dependently protected from the cytotoxicity of AAPH-derived alkoxyl radicals (p < 0.05); besides, the de novo glutathione biosynthesis and regeneration of GSH from oxidized form was also increased in these cells. In corroboration with the biochemical parameters, the Nrf2/HO1 expression was upregulated by the BHE pretreatment concomitantly reducing the cellular lipid peroxidation products. The improvement glutathione biosynthesis was also observed in BHE alone treated cells.
Conclusion: The study indicated the potential of methanolic extract of Borassus flabellifer haustorium in enhancing the de novo glutathione biosynthesis in normal and pro-oxidant exposed cells by Nrf2/HO1 dependent manner, concomitantly mitigating the toxicity of AAPH-derived alkoxyl radicals in intestinal epithelial cells.
Keywords: Borassus flabellifer; Antioxidant activity; Cytoprotection; Glutathione metabolism; Haustorium extract; Nrf2 signaling.