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BACKGROUND: Along with aging, antioxidase activity decreases and oxygen-derived free radicals greatly accumulate, resulting in cellular senescence, or even cell death. This is manifested by hypomnesia and disordered metabolism of free radicals. Studies have reported that Longyanshen polysaccharidcs have the function of antioxidation and improved brain memory.OBJECTIVE: To observe the effects of Longyanshen polysaccharides on free radical metabolism in brain tissue to verify the anti-aging mechanisms in senescence accelerated-prime (SAMPS) mice. DESIGN, TIME AND SETTING: The randomized, controlled, biochemical experiment was performed in the Department of Pharmacology and Scientific Experimental Center of Guangxi Medical University (China) from September 2005 to January 2008.MATERIALS: Forty SAMP8 mice were randomized into four groups: SAMP8 control group, as well as low-, mid-, and high-dose polysaccharide, with 10 mice in each group. Ten senescence accelerated-resistant-prone (SAMR 1) mice served as the normal control group. Longyanshen polysaccharides, extracted from the medical plant Longyanshen, were supplied by the Department of Pharmacology, Guangxi Medical University. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malonaldehydc (MDA), nitric oxide (NO), and total protein test kitwere purchased from Nanjing Jiancheng Bioengineering Institute (China).METHODS: SAMP8 mice were used to establish a dementia animal model. SAMP8 and SAMRI control mice were administered 30 mL/kg saline. The low-, middle-, and high-dose polysaccharide groups were administered 45, 90, and 180 mg/kg Longyanshen polysaccharides, respectively. Each group was treated by intragastric administration, once daily, for 50 continuous days.MAIN OUTCOME MEASURES: One hour after the last administration, mouse brain tissues were collected, and retro orbital blood sampling was performed. Spectrophotometry was used to measure SOD and GSH-Px activity, as well as MDA and NO concentration in sera and brains of SAMP8 mice.RESULTS: SOD and GSH-Px activity decreased significantly, and MDA and NO concentration increased significantly, in SAMP8 control group brain tissues, compared with the SAMPI control group (P < 0.05). Compared with the SAMP8 control group, Longyanshen polysaccharide-treated groups exhibited enhanced SOD and GSH-Px activity, as well as decreased MDA and NO concentration, in serum and brain tissue (P < 0.05). Longyanshen polysaccharides exerted a similar effect on SOD, GSH-Px, MDA, and NO concentrations in serum and brain tissues of SAMP8 mice.CONCLUSION: Longyanshen polysaccharides scavenged free radicals effectively, reduced NO concentration and ameliorated NO toxicity, thereby influenced aging and stress, as well as improving memory capacity in the brain.