Ultrasonic-assisted extraction (UAE) of American ginseng polysaccharides (AGP) was investigated using response surface methodology. Three-factor-three-level Box-Behnken design was employed to optimize the ultrasonic power, extraction time and ratio of water to raw material to obtain a high AGP yield. The analysis of variance and response surface plots indicated that ultrasonic power was the most important factor affecting the extraction yield. The optimal conditions were ultrasonic power 400 W, extraction time 71 min, and ratio of water to raw material 33 mL g-1. Under these conditions, the yield of AGP was 8.09%, which was agreed closely to the predicted value. Gas chromatography (GC) analysis showed that AGP was composed of arabinose, rhamnose, galactose, glucose, and galacturonic acid. Fourier transform infrared spectra revealed the general characteristic absorption peaks of AGP. In addition, AGP exhibited good immunostimulating activities by up-regulating the production of nitric oxide and cytokines. Compared with hot water extraction, UAE required shorter extraction time and gave a higher extraction yield, without changing the structure and immunostimulating activity of AGP. The results indicated that UAE could be an effective and advisable technique for the large scale production of plant polysaccharides.

Ginsenosides Rg1, Rb1, R1, Rd, and Re are major constituents of Panax notoginseng, a famous traditional Chinese medicinal herb, which has both stimulative and inhibitory effects on the central nervous system (CNS). The monoamine hypothesis proposes that depression is a result of the depletion of 5-hydroxytryptamine (5-HT), norepinephrine (NE) and dopamine (DA) in addition to the activation of monoamine oxidase in the CNS. The purpose of this study was to determine whether P. notoginseng Saponin (PNS) has an antidepressant activity. We investigated the antidepressant-like activities of Rg1, Rb1, R1, Rd, and Re in mice, using two animal models of depression. In addition, we analyzed the neurochemicals by the chronic unpredictable mild stress test. Our results showed that Rb1, Rd, and Re treatment at 10 mg kg-1 significantly reduced the duration of immobility in both the tail suspension and forced swimming tests. Rb1, Rd, and Re increases in 5- HT and NE levels at 10 mg kg-1 in both the frontal cortex and hippocampus. Dopamine levels increased in the hippocampus and the striatum. Moreover, 5-hydroxyindoleacetic acid (5-HIAA) levels were found increased in the hippocampus. These findings suggest that the antidepressant effects of Rb1, Rd, and Re may be related to the increase in 5-HT and NE in the CNS, and through the alterations in the synthesis or metabolism of dopamine.