Neuroprotective Effect of Phyllanthus acidus L. on Learning and Memory Impairment in Scopolamine-Induced Animal Model of Dementia and Oxidative Stress: Natural Wonder for Regulating the Development and Progression of Alzheimer’s Disease

Nature is the best source of complementary and alternative medicine. The plant Phyllanthus acidus (PA) L. has been used traditionally in pain, inflammatory and oxidative stress related disorders. In this consequence, methanolic extract of PA (MEPA) was selected to explore the ability of this plant to enhance cognitive function, brain antioxidant enzymes and anti-acetylcholinesterase activity which can be used for the treatment of oxidative stress related disorders like Alzheimer’s disease (AD). The purpose of this study was to investigate the neuroprotective effect of MEPA on learning and memory impairment in scopolamine-induced rats of dementia and oxidative stress. Treatment with MEPA (i.e., 100 and 200 mg/kg b.w.) was investigated in scopolamine-treated Swiss albino male rats for 14 days and its neuroprotective effects were examined using Elevated Plus Maze (EPM) test, Passive Avoidance (PA) test, Novel Object Recognition (NOR) test, Morris Water Maze (MWM) test as well as level of antioxidant enzymes such as catalase (CAT), super oxide dismutase (SOD), glutathione reductase (GSR), glutathione-S-transferase (GST), reduced glutathione (GSH), glutathione peroxidase (GSH-Px), lipid peroxidation (TBARS) contents and acetylcholinesterase (AChE) activity in rat brain tissue homogenates. Administration of MEPA significantly (P < 0.05, P < 0.01; P < 0.01) decreased RTL (retention transfer latency) in rats on 7th and 14th day compared to the disease control and control group in the EPM test. In PA test the doses of MEPA suggestively (P < 0.05, P < 0.001; P < 0.05, P < 0.01) increased STL (step-through latency) in rats on 7th and 14th day with respect to disease control and control group. For NOR test administration of MEPA considerably (P < 0.01, P < 0.001; P < 0.01) increased the DI (discrimination index) in rats with respect to that of disease control and control group. The doses of MEPA markedly (P < 0.05, P < 0.01; P < 0.01) decreased EL (escape latency) and significantly (P < 0.01, P < 0.001; P < 0.05, P < 0.01) increased TSTQ (time spent in the target quadrant) on successive days as compared to that of disease control and control group in the acquisition trial of MWM test. In case of probe trial of MWM test MEPA administration considerably (P < 0.01; P < 0.05, P < 0.01) increased TSTQ and significantly (P < 0.05, P < 0.01; P < 0.05, P < 0.01) increased TSA (time spent in the annuli) in rats on successive days as compared to that of disease control and control group. MEPA administration significantly (P < 0.05, P < 0.01, P < 0.001; P < 0.05, P < 0.01) increased the level of CAT, SOD, GSR, GST GSH, GSH-Px and markedly (P < 0.01; P < 0.01, P < 0.001) decreased TBARS level through inhibiting lipid peroxidation as well as significantly (P < 0.01, P < 0.001; P < 0.05, P < 0.01, P < 0.001) decreasing AChE activity in rats brain compared to the disease control and control group. The present study demonstrates that MEPA showed the neuroprotective effect by improving cognitive functions and reduces oxidative stress by increasing the level of brain antioxidant enzymes as well as decreasing lipid peroxidation and acetylcholinesterase activity. Therefore, this plant extract can be used for enhancing learning, memory, antioxidant potentiality and anti-acetylcholinesterase activity in neurodegenerative disorders like AD.