Effects of lotus-derived constituents on learning and memory activity of scopolamine-induced mice

Abstract

Various reactive oxygen species (ROS), such as singlet oxygen (1O2), superoxide radical, hydrogen peroxide, and hydroxyl radical, are generated as by-products during the aerobic metabolisms in cells. If the production of free radicals exceed the antioxidant capacity of a living system, free radicals not only attack to cells enzymes and DNA, protein, and lipid, but also cause numerous disorders such as brain dysfunction immune system decline, heart disease, or Alzheimers disease. Antioxidants can prevent oxidative damages, increased intakes from the diet will also reduce the risks of numerous diseases. An assessment was made of the antioxidant activity of the constituents derived from Indian lotus, Nelumbo nucifera Gaertner (Nelumbonaceae), using 2,2-diphenyl-1-picrylhydrazyl assay. Results were compared with those of a commonly used antioxidant ascorbic acid. The biologically active constituents were determined to be the simple benzoic acid 3,4-dihydroxy benzoic acid and the flavone luteolin from the roots and the flavonol isoquercetin from the leaves. Based on fifty percent inhibition concentration (IC50), 3,4-dihydroxy benzoic acid (10.90 µM) was the most antioxidant compound and was ≈5 times more active than ascorbic acid (58.19 µM). The antioxidant activity of luteolin and ascorbic acid did not differ significantly. IC50 of isoquercetin was 123.23 μM. In addition, the Morris water maze is used for examining the effects of luteolin and tacrine on the learning and memory activity of scopolamine-induced cognitive impairment mice. The scopolamine-treated group (0.5 mg/kg, i.p.) exhibited longer latency time than the saline-treated control group during the 5 days. However, luteolin (20 mg/kg) or tacrine (10 mg/kg) plus scopolamine-treated groups showed significantly shorter latency time than the scopolamine-treated group during the experimental period. Results of distance to platform was similar with those of latency time. Further studies will warrant possible applications of luteolin as potential antioxidant products for the eradication from oxidative stress and increasing learning and memory.