Effects of Arsenic Treatments on Saponin Content and Heterogeneity Extracted from Rhizome and Main Root of Panax notoginseng Plants Grown in Shaded Field
Effects of Arsenic Treatments on Saponin Content and Heterogeneity Extracted from Rhizome and Main Root of Panax notoginseng Plants Grown in Shaded Field
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DOI：
10.4236/gep.2016.47003
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发表时间：
2016-07
期刊：
影响因子：
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通讯作者：
Y. Zu;Jinjing Sun;N. Ma;Q. Min;G. Feng;Jiong Wu;Yuan Li
中科院分区：
文献类型：
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作者：
Y. Zu;Jinjing Sun;N. Ma;Q. Min;G. Feng;Jiong Wu;Yuan Li
污染是影响三七质量安全的重要因素之一。皂苷是三七中具有重要药用价值的化合物之一。土壤砷对三七生产皂苷的影响目前所知甚少。研究了土壤中不同浓度砷处理对三七总皂苷含量和异质性的影响，并探讨了其作用机制。采用0、20、80、140、20和260 mg/kg浓度的砷（As (V)）作为砷酸钠（Na3AsO4）处理三七植株。这些实验植物在温室的荫蔽条件下生长。植物分别在旺盛的营养生长和果实成熟阶段收获。测定了不同砷处理对三七皂苷与人参皂苷混合物中皂苷含量、单体异质性、角鲨烯合成酶酶活性和基因表达水平的影响。结果表明：(1)从最低浓度到最高浓度，处理植株的根茎和主根的砷含量均在三七优质品的标准范围内。果实成熟期除主根外，其余组织中三七皂苷含量均高于《中国药典》规定的标准含量5%；(2) 20 mg/kg砷处理后，根茎和主根总皂苷含量分别增加3.5% ~ 183.9%。最高As浓度为260 mg/kg时，三七总皂苷含量显著下降，角鲨烯合成酶酶活性和基因表达水平降低；(3) As处理下，根状茎和主根中Rb1/Rg1比值降低，(Rb1 + Rg1)/R1比值升高。综上所述，低砷浓度（20 ~ 80 mg/kg）处理能显著提高三七皂苷含量。然而，高浓度砷处理有不良反应。三七皂苷的合成受到抑制，丙二醇转化为丙三醇的过程中断，导致三七皂苷含量较低，单体混合物较不均匀。最高砷浓度260 mg/kg处理后，角鲨烯合成酶的基因表达和酶活性均受到抑制，导致根茎和主要根组织中皂苷含量显著降低。
As contamination is one of important factors to Panax notoginseng quality and safety. Saponin is one of important compounds with the medicinal values of P. notoginseng. The impact of soil As on production of saponin of P. notoginseng knew very little. This study was performed to determine content and heterogeneity of saponins from P. notoginseng and its mechanisms upon treatments with different concentration levels of As in soil. Plants of P. notoginseng were treated with arsenic [As (V)] at 0, 20, 80, 140, 20 and 260 mg/kg concentration levels which were supplied as sodium arsenate (Na3AsO4). These experimental plants were grown in shade condition in a greenhouse. Plants were harvested at vigorous vegetative growth and fruit ripening stages, separately. Effects of As treatments on saponin content, and heterogeneity of monomers in the mixtures of notoginesenosides and ginsenosides, enzymatic activity and gene expression level of squalene synthetase were determined for rhizome and main root tissues. Results show that：(1) Of all the As treatments from the lowest to the highest concentration levels, the As content in both rhizome and main roots from As-treated plants was within the standard level for superior products derived from P. notoginseng. The content of notoginsenosides from all tissues except the main roots at fruit ripening stage, was 5% higher than the standard level specified in the Chinese Pharmacopoeia; (2) The treatment of As at 20 mg/kg led to an 3.5% - 183.9% increases in total notoginesenosides content in rhizome and main roots, respectively. Treatments with the highest As concentration at 260 mg/kg resulted in a significant decline in total notoginsenosides content, and lower enzymatic activity and gene expression levels of squalene synthetase; (3) Under As treatment conditions, the ratio of Rb1/Rg1 decreased but the ratio of (Rb1 + Rg1)/R1 increased in both rhizomes and main roots. Conclusively, this study demonstrated that low As concentration (20 - 80 mg/kg) treatments resulted in higher notoginsenoside content in P. notoginseng. However, treatments with high As concentrations had an adverse effect. The repression in the synthesis of notoginsenoside and interruption of the conversion process from propanaxadiol into propanaxatriol are responsible for more heterogeneous monomer mixtures and low notoginsenoside content. For plants treated with the highest As concentration of 260 mg/kg, both gene expression and enzymatic activities of squalene synthetase were greatly repressed thus leading to a significantly low saponin content in rhizome and main root tissues.