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Panax quinquefolium (American ginseng) is a perennial understory herb that has been widely used as a medicinal plant in China and other countries. Autotoxicity has been reported to be one of the major problems hindering the consecutive cultivation of American ginseng. However, the potential autotoxic compounds produced by the root of American ginseng are less well known. Here, we report the isolation and characterization of five groups of autotoxic compounds from aqueous extracts of the fibrous roots of American ginseng. Ether extracts of the water-soluble compounds were further analyzed and separated into seven fractions. Among them, the most autotoxic fraction (Fraction V) was subjected to GC/MS analysis, and 44 compounds were identified. Based on literature information, 14 individual compounds were selected and their autotoxic effects on seedling growth were further tested. The results revealed that, of these 14 compounds, 9 phenolic compounds significantly reduced the growth of seedlings in a concentration-dependent manner, while 5 aliphatic compounds showed modest inhibition at all three concentrations tested. Furthermore, we verified the existence of the autotoxic compounds in the plow layer soil of commercially cultivated American ginseng fields, and the concentration of these compounds as determined by HPLC analysis was in line with the concentration determined to be bioactive. Taken together, our study established a functional link between the compounds produced by American ginseng and their autotoxic effects.

Polo-like kinases (PLKs) family has long been known to be critical for cell cycle and recent studies have pointed to new dimensions of PLKs function in the nervous system. Our previous study has verified that the levels of PLK3 in the brain are severely downregulated in prion-related diseases. However, the associations of PLKs with prion protein remain unclear. In the present study, we confirmed that PrP protein constitutively interacts with PLK3 as determined by both in vitro and in vivo assays. Both the kinase domain and polo-box domain of PLK3 were proved to bind PrP proteins expressed in mammalian cell lines. Overexpression of PLK3 did not affect the level of wild-type PrP, but significantly decreased the levels of the mutated PrPs in cultured cells. The kinase domain appeared to be responsible for the clearance of abnormally aggregated PrPs, but this function seemed to be independent of its kinase activity. RNA-mediated knockdown of PLK3 obviously aggravated the accumulation of cytosolic PrPs. Moreover, PLK3 overexpression in a scrapie infected cell line caused notable reduce of PrP(Sc) level in a dose-dependent manner, but had minimal effect on the expression of PrP(C) in its normal partner cell line. Our findings here confirmed the molecular interaction between PLK3 and PrP and outlined the regulatory activity of PLK3 on the degradation of abnormal PrPs, even its pathogenic isoform PrP(Sc). We, therefore, assume that the recovery of PLK3 in the early stage of prion infection may be helpful to prevent the toxic accumulation of PrP(Sc) in the brain tissues.

In China, about 40% of traditional Chinese medicine (TCM) comes from cultivation in agrarian systems. The cropland is fundamental to the productions of medicinal plants, and the sustainable soil management is essential for sustainable using of the TCM resources, furthermore it affects the local economies of the medicinal plant production regions and the sustainable development of TCM agriculture. In this paper, the concept of the sustainable use of TCM cropland was discussed and the problems on sustainable soil management in China were analyzed from the aspects of resources and quality. The research advances in sustainable use of the medicinal plants cropland were reviewed from the aspects of continuous cropping obstacles, faming systems and degraded soil remediation. The strengthening research fields in the further were suggested.

To provide evidence for establishing an efficient method of growing Panax quinquefolium by rotation of crops.Four-year old P. quinquefolium was cultivated in water and soil cultures. Biological assays were conducted with the aqueous extracts of P. quinquefolius, Fructus Perillae and roots of Coix lacryma-jobi. P. quinquefolium was cultivated in the soil where purple Perilla frutesens and C. lacryma-jobi were grown previously. The effects of rotation were determined.The stems, leaves and fibrous roots of Panax quinquefolium contained allelopathic substances. When the concentration of the allelopathic substances exceeded 1g per kg soil, P. quinquefolius could not grow. On the other hand, when the concentration of allelopathic substances fell below 0.2 g per kg soil, the rate of seedling growth was decreased by 25%. When P. quinquefolius was cultivated in the soil in which purple Perilla frutesens had previously grown, or in the soil supplemented with Fructus Perillae, the rates of seedling growth and the yield were raised by 26.8% and 11.5% tively, in comparison with the controls.Rotation of Panax quinquefolium and Perilla frutesens was shown to be a good way for the cultivation of the former. During the growing process, application of Fructus Perillae to the soil could further enhance the growth and of Panax quinquefolium.

To provide basis of environmental factors of genuine crude drug, Salvia miltiorrhiza root.On-the-spot investigation and indoor chemical analysis were made to study the physicochemical properties of growing soil and content of inorganic elements of S. miltiorrhiza, and obtained data were analysed with SPSS 10.0 software.S. miltiorrhiza root of high harvest area accumulated Cu and Zn. In soil principal component analysis, no principal component was obvious. So the drug has good adaptability in ecological environment of soil.Ecological environment of soil isn't leading factor in forming genuine crude S. miltiorrhiza.

To provide basis for environmental factors of genuine crude Chinese angelica.On-the-spot investigation and indoor chemical analysis were made to study the physicochemical properties of cultivated soil of Chinese angelica.The physical properties and the organic matte and mineral nutrition of cultivated soil of Chinese angelica are best in Min County, Gansu Province. The ecological environment is the leading factor in forming genuine crude Chinese angelica.