TITLE:
Effects of Arsenic Treatments on Saponin Content and Heterogeneity Extracted from Rhizome and Main Root of Panax notoginseng Plants Grown in Shaded Field
AUTHORS:
Yanqun Zu, Jinjin Sun, Ni Ma, Qiang Min, Guangquan Feng, Jiong Wu, Yuan Li
KEYWORDS:
Panax notoginseng, Saponin, As, Squalene Synthase, Gene Expression
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.4 No.7,
July
22,
2016
ABSTRACT: 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 bothrhizomes 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.