Neuroprotective effects of Peltophorum pterocarpum leaf extract against hydrogen peroxide induced oxidative stress and cytotoxicity

Abstract Background Peltophorum pterocarpum is a plant from the family of Leguminosae and a tropical tree found in South East Asia region. The leaves of the plant is rich in anti-oxidant polyphenols. Traditionally this plant was used to cure intestinal disorders and as a relief for sprain, bruise, muscular pain and sores and for pain during child birth. Since oxidative stress is a major contributing factor towards neurodegenerative diseases the leaves of this plant was explored for its neuroprotective properties. Method In this study, we report the neuroprotective properties of the ethanolic extract of Peltophorum pterocarpum leaf against oxidative stress induced cell death by H2O2, in an in vitro model of neuronally differentiated IMR32 neuroblastoma cells. Hydrogen peroxide was used as an inducer for oxidative stress. Cell viability was determined using MTT assay, apoptosis studies were carried out using Annexin V-FITC and Caspase 3 assays, mitochondrial membrane potential was examined using JC1 staining. The oxidative stress induced by H2O2 was determined by quantifying the intracellular reactive oxygen species production using DCF-DA staining. Mitogen activated protein kinase signaling pathway of the neuroprotective effect of PTE was also elucidated since oxidative stress activates this pathway signaling. Results Peltophorum pterocarpum leaf extract did not exhibit any cytotoxicity to differentiated IMR32 cells at the tested concentration of 7.8 μg/ml till 250 μg/ml. Pre-treatment of differentiated IMR32 with Peltophorum pterocarpum leaf extract prior to exposure to 300 μM hydrogen peroxide significantly ameliorated neuronal cell death and apoptosis in a dose-dependent manner. Hydrogen peroxide induced oxidative stress caused the reduction of mitochondrial membrane potential in differentiated IMR32 cells. Peltophorum pterocarpum leaf extract conferred neuroprotection to differentiated IMR32 by increasing the mitochondrial membrane potential in a dose-dependent manner which was significantly higher at 125 μg/ml and 250 μg/ml. PTE pre-treatment attenuated the increase of intracellular reactive oxygen species induced by hydrogen peroxide in a dose-dependent manner up till concentration of 125 μg/ml. Western blot analysis on mitogen activated protein kinases (MAPKs) revealed that neuroprotection of Peltophorum pterocarpum leaf extract against hydrogen peroxide induced cytotoxicity was achieved by complete inhibition of the activation of phospho-p-38 phosphorylation and attenuation of phospho-ERK1/2. Conclusion This study thus suggests that Peltophorum pterocarpum leaf extract has neuroprotective activity against oxidative-stress induced neuronal cell death