Lipoprotein lipase activation by red ginseng saponins in hyperlipidemia model animals.

The effect of ginseng saponins isolated from red ginseng (a steamed and dried root of Panax ginseng) has been studied in a cyclophosphamide (CPM)-induced hyperlipidemia model in fasted rabbits. In this model, chylomicrons and very low density lipoprotein (VLDL) accumulation was known to occur as a result of reduction in lipoprotein lipase (LPL) activity in the heart and heparin-releasable heart LPL. Oral administration of ginseng saponins at a dose of 0.01 g/kg for 4 weeks was found to reverse the increase in serum triglycerides (TG) and concomitant increase in cholesterol produced by CPM treatment, especially in chylomicrons and VLDL. In addition, ginseng saponins treatment led to a recovery in postheparin plasma LPL activity and heparin-releasable heart LPL activity, which were markedly reduced by CPM treatment. In rats given 15% glycerol/15% fructose solution, postheparin plasma LPL activity declined to two third of normal rats, whereas ginseng saponins reversed it to normal levels. In the present study we first demonstrated that ginseng saponins sustained LPL activity at a normal level or protected LPL activity from being decreased by several factors, resulting in the decrease of serum TG and cholesterol.     

Comparison of synthetic saponin cholesterol absorption inhibitors in rabbits: evidence for a non-stoichiometric, intestinal mechanism of action

The hypocholesterolemic activities of pamaqueside and tiqueside, two structurally similar saponins, were evaluated in cholesterol-fed rabbits. The pharmacological profiles of the saponins were virtually identical: both dose-dependently decreased the intestinal absorption of labeled cholesterol 25-75%, increased fecal neutral sterol excretion up to 2.5-fold, and decreased hepatic cholesterol content 10-55%. High doses of pamaqueside (>5 mg/kg) or tiqueside (>125 mg/kg) completely prevented hypercholesterolemia. Decreases in plasma and hepatic cholesterol levels were strongly correlated with increased neutral sterol excretion. Ratios of neutral sterol excreted to pamaqueside administered were greater than 1:1 at all doses, in opposition to the formation of a stoichiometric complex previously suggested for tiqueside and other saponins. Ratios in tiqueside-treated rabbits were less than unity, a reflection of its lower potency. Pamaqueside-treated rabbits exhibited a more rapid decline in plasma cholesterol concentrations than control animals fed a cholesterol-free diet, indicating that the compound also inhibited the absorption of biliary cholesterol. Intravenous administration of pamaqueside had no effect on plasma cholesterol levels despite plasma levels twice those observed in rabbits given pamaqueside orally.These data indicate that pamaqueside and tiqueside induce hypocholesterolemia by blocking lumenal cholesterol absorption via a mechanism that apparently differs from the stoichiometric complexation of cholesterol hypothesized for other saponins.     

The influence of saponins on cell membrane cholesterol

We studied the influence of structurally different saponins on the cholesterol content of cellular membranes. Therefore a cell culture model using ECV-304 urinary bladder carcinoma cells was developed. To measure the cholesterol content we used radiolabeled ³H-cholesterol which is chemically and physiologically identical to natural cholesterol. The cells were pre-incubated with ³H-cholesterol and after a medium change, they were treated with saponins to assess a saponin-induced cholesterol liberation from the cell membrane. In another experiment the cells were pre-incubated with saponins and after a medium change, they were treated with ³H-cholesterol to assess a saponin-induced inhibition of cholesterol uptake into the cell membrane. Furthermore, the membrane toxicity of all applied saponins was analyzed using extracellular LDH quantification and the general cytotoxicity was analyzed using a colorimetric MTT-assay and DNA quantification. Our results revealed a correlation between membrane toxicity and general cytotoxicity. We also compared the results from the experiments on the saponin-induced cholesterol liberation as well as the saponin-induced inhibition of cholesterol uptake with the membrane toxicity. A significant reduction in the cell membrane cholesterol content was noted for those saponins who showed membrane toxicity (IC₅₀ <60 μM). These potent membrane toxic saponins either liberated ³H-cholesterol from intact cell membranes or blocked the integration of supplemented ³H-cholesterol into the cell membrane. Saponins with little influence on the cell membrane (IC₅₀ >100 μM) insignificantly altered the cell membrane cholesterol content. The results suggested that the general cytotoxicity of saponins is mainly dependent on their membrane toxicity and that the membrane toxicity might be caused by the loss of cholesterol from the cell membrane.We also analyzed the influence of a significantly membrane toxic saponin on the cholesterol content of intracellular membranes such as those of endosomes and lysosomes. In these experiments ECV-304 cells were either incubated with ³H-cholesterol or with ³H-cholesterol and 5 μM saponin. After isolation of the endosomes/lysosomes their ³H-cholesterol content was measured. A significant influence of the saponins on the cholesterol content of endosomal/lysosomal membranes was not detected.     

Acyl-CoA: cholesterol acyltransferase inhibitory activity of ginseng sapogenins, produced from the ginseng saponins.

Ginseng sapogenins were produced from ginseng saponins, isolated from Korean ginseng roots. Ginseng saponins very mildly inhibited acyl-CoA:cholesterol acyltransferase (ACAT) in vitro, however, the sapogenins showed strong inhibitory activity on microsomal ACAT. Therefore, the sapogenins will be one of key ingredients of ginseng affected a lowering of the serum total cholesterol level.     

Cholesterol-independent membrane disruption caused by triterpenoid saponins

The membrane-disrupting activity of 15 triterpenoid saponins, obtained from Chinese plants of the genus Aralia, was investigated using phosphatidylcholine liposomes with and without cholesterol. The permeability of the membrane was examined by monitoring the induced fluorescent dye release from the liposome. On the basis of the obtained results, the structure-activity relationship among glucuronides of oleanolic acid was discussed. This takes into account particularly the variation in the carboxyl function. Namely, the saponins could induce a permeability change on liposomal membrane without cholesterol when they are glycosylated at both C-3 and C-28 of the oleanolic acid. There also exists a great similarity in the time-course curves for dye-release within such saponins, reflecting their similar action with the lipid bilayer membrane. The saponins glycosylated only at C-3 could also exhibit the same activity with somewhat different action profiles when the glucuronic acid is esterified, while those with the free glucuronic acid required cholesterol in the liposomes to induce permeability change thereof.     

Interaction of sea cucumber saponins with multilamellar liposomes

The effect of three sea cucumber saponins, echinoside A, bivittoside D and holothurin A, on multilamellar liposomes was investigated. An ideal osmotic behavior of liposomes was described as a linear relationship between the reciprocal $\text{3}\text{2}\text{s}$ power of absorbance at 450 nm and the osmotic gradient across the membrane. Sea cucumber saponins at concentrations below critical micelle concentration (CMC) disturbed this linear relationship in liposomes composed of egg phosphatidylcholine, phosphatidic acid and cholesterol. Cholesterol-free liposomes were not susceptible to these saponins. Results of optical measurements were consistent with those of transmission electron microscopy, which showed saponin-induced changes in liposomal structure. The lytic activity of sea cucumber saponins on liposomes depended on their chemical structure.These results suggest that sea cucumber saponins as monomers can interact with liposomes and that cholesterol serve as a principal binding site for the sea cucumber saponins.     

乌拉尔甘草根的结构与皂苷类成分积累关系研究

应用植物解剖学、组织化学定位和植物化学方法,对不同发育阶段的乌拉尔甘草根中的皂苷类成分的积累变化规律进行了研究,为进一步揭示甘草药材质量形成的内在机制并指导优质甘草栽培提供理论依据.结果表明:(1)乌拉尔甘草中皂苷类成分主要存在于根的韧皮薄壁细胞和射线细胞中,韧皮部中皂苷含量高于木质部和根皮,而且根的次生生长与皂苷类成分的积累具有一定的相关性.(2)不同生长年限的乌拉尔甘草根中的总皂苷含量存在差异,3年生甘草根中总皂苷含量高于2年生和1年生甘草根.     

Induction and Characterization of Adventitious Roots Directly from the Explants of <Emphasis Type="Italic">Panax notoginseng</Emphasis>

Adventitious roots from leafstalks and lateral roots were obtained directly from explants of Panax notoginseng. The lateral root explants were more sensitive to the induction of adventitious roots using indole-3-butyric acid. HPLC analysis of saponins extracted from the adventitious roots indicated that several protopanaxatriol saponins were present but ginsenoside Rd was missing, compared with the saponins extracted from the raw herbs. The dry weight of primary adventitious root culture of Panax notoginseng increased 5.25 times during multiplication in a classical shaking-flask system, suggesting that it is a culture system with great potential for scale-up. Revisions requested 13 July 2005; Revisions received 1 September 2005     

牛膝根的结构发育与三萜皂苷积累的关系

应用植物解剖学、组织化学定位及植物化学技术,研究了不同发育时期牛膝根的结构特征与三帖皂苷积累的关系。结果表明:牛膝根的初生结构和次生结构类似于一般双子叶植物,其根的加粗主要是由于三生结构的发生和分化。第一圈额外形成层产生于次生韧皮部外侧的薄壁组织细胞和射线细胞,以后的每一圈由前一圈向外衍生的薄壁组织细胞产生。额外形成层无纺锤状原始细胞和射线原始细胞之分,在切向纵切面上呈叠生排列。三生维管束以离心方式排成整齐的同心环状,由薄壁结合组织将其彼此分开,其圈数与额外形成层的圈数是一致的,随着根的个体发育而不断增加。在根的初生结构中,三萜皂苷主要分布于中柱鞘、初生韧皮部及初生韧皮部和初生木质部之间的薄壁组织细胞内;在根的次生结构中,主要分布于次生韧皮部及栓内层的薄壁组织细胞内。当三生结构形成后,除次生韧皮部及栓内层细胞外,在额外形成层和三生维管束韧皮部细胞内均有皂苷类物质积累。三生结构在牛膝根中占主要地位,是三萜皂苷积累与分布的主要场所。在牛膝根的生长发育过程中,三萜皂苷元齐墩果酸的百分含量呈“S”型曲线增长,其根的增长、加粗、三生维管束圈数、三萜皂苷总量及根中干重的积累量都在出苗后约120天达到高峰,此时应为牛膝根的最佳采收期。     

卵叶远志营养器官的结构及远志皂苷的组织化学定位和含量测定

应用植物解剖学、组织化学定位和高效液相色谱法,研究了卵叶远志各营养器官的结构、远志皂苷积累分布状态及含量变化。结果表明．卵叶远志的根包括周皮和次生维管组织两部分．周皮发达,次生韧皮部较厚,韧皮薄壁细胞为其主要成分。次生木质部中导管和纤维发达,导管分布密度较大。茎包括表皮、皮层、维管柱三部分,在皮层与韧皮部之间具有一圈排列紧密的厚壁细胞．推测这圈厚壁细胞具有质外体屏障作用．可保护茎组织免受干旱的伤害。叶为异面叶。根茎的结构表现为旱生特点。组织化学显示远志皂苷在根中分布在次生韧皮部和栓内层：在茎中分布在表皮、皮层和次生韧皮部细胞中：在叶中则分布在叶肉组织和表皮中。根的次生韧皮部为皂苷积累储存的主要场所。高效液相测定结果显示营养器官中都有远志皂苷元的积累．根中的含量高．茎叶中含量较低．说明卵叶远志地上部分也有药用价值。根据不同发育时期根和茎叶中皂苷元的动态变化趋势．建议在5月份（花果期）进行卵叶远志的采收。     

Membranotropic effect of some triterpene glycosides possessing immunostimulating properties

The peculiarities of the interaction between cell membrane lipids and triterpene glycosides from holothurians Apostichopus japonicus S. and Cucumaria japonica (holotoxin A1 and cucumarioside A2-2, respectively) were studied in comparison with plant saponins from Quillaja saponaria, known as hemolytic, adjuvant, and structure-forming components of immunostimulating complexes. Similar to Quillaja saponins, the sea glycosides, holotoxin A1 and cucumarioside A2-2 were shown to possess a high hemolytic activity (2.6 and 3 microg/ml, respectively) and sterol-depending membranotropic effect mediated by the formation of nonbilayer sterol-lipid-glycoside complexes. At the same time, cucumarioside A2-2 bound exogenic cholesterol only in the presence of membrane lipids, such as phosphatidylcholine or monogalactosyldiacylglycerol, in contrast to Quillaja saponins and holotoxin A1, which bound cholesterol in the molar ratios 1:2 and 1:8, respectively. Moreover, in all cases, tree-component complexes containing cholesterol, lipid, and glycoside exhibited a lower hemolytic activity compared with two-component sterol-glycoside complexes. It was concluded that the hydrophobic medium of cell membranes performs a potentiative role in the effective interaction between triterpene glycosides and "sterol receptors". A method for decreasing the toxicity of membranotropic holothurian glycosides possessing the immunomodulating properties was suggested.     

The susceptibility of cholesterol-depleted erythrocytes to saponin and sapogenin hemolysis

The assumption that complex formation between erythrocyte membrane cholesterol and saponins or sapogenins is the cause for their hemolytic activity, was tested by measuring the susceptibility of cholesterol-depleted erythrocytes towards these hemolysins. For some of the hemolysins cholesterol depletion caused inhibition of hemolysis, for others an augmentation. The results suggest that cholesterol does not serve as a specific binding site for these hemolysins.     

Effect of dietary saponins from Quillaja saponaria L. on fatty acid composition and cholesterol content in muscle Longissimus dorsi of lambs

The purpose of this study was to evaluate the effects of increasing levels of saponins from Quillaja saponaria on fatty acid (FA) composition and cholesterol content in muscle Longissimus dorsi of lambs. A total of 24 Barbarine lambs were assigned to four dietary treatments: control diet (C) consisting of oat hay ad libitum and 400 g of concentrate (80% barley, 17.5% soybean meal and 2.5% vitamin and mineral supplement); C diet plus 30 ppm of Q. saponaria L. (QS30); C diet plus 60 ppm of Quillaja (QS60); C diet plus 90 ppm of Quillaja (QS90). Saponin supplementation reduced the concentration of C14:1 cis-9 (P = 0.001) and of its desaturation index (P = 0.002). None of the FA intermediates of ruminal biohydrogenation (BH) was affected by Quillaja saponin supplementation (P > 0.05). The concentration of C20:4n-6 was higher in the meat of animals receiving 60 ppm of Quillaja than C and QS30 groups. Supplementing 60 ppm of Quillaja reduced the ratio between α-linolenic and linoleic acids compared with the C group (P = 0.023). We did not find any significant effect of Quillaja saponins on muscle cholesterol level. Further investigations are necessary to assess the metabolic fate of saponins in the rumen and to understand whether there is an effect of saponin on Δ9-desaturase enzyme activity, ruminal BH and cholesterol metabolism in ruminants. Supplementing up to 90 ppm of Quillaja saponins did not produce detrimental effects on the overall meat FA profile.     

Incorporation of [4-14C] cholesterol into steryl derivatives and saponins of oat (Avena sativa L.) plants

Sterols from both green and etiolated oat plants (Avena sativa) contain sitosterol, stigmasterol, cholesterol, ⁷-stigmastenol, ⁷-cholestenol and campesterol. In the saponin fraction avenacosides A and B and 26-desgluco-avenacosides A and B were detected. Etiolated plants incorporated [4-¹⁴C] cholesterol into steryl derivatives (esters, glycosides and acylated glycosides) and also into all of the 4 saponins. [4-¹⁴C] sitosterol, however, is incorporated only into steryl derivatives, but not in saponins. From this it is concluded that cholesterol, but not sitosterol is the in vivo precursor of oat saponins.Abbreviations GLC gas liquid chromatography - I.D. inner diameter - TMS trimethylsilyl - dpm decompositions per minute     

Mannosylated saponins based on oleanolic and glycyrrhizic acids. Towards synthetic colloidal antigen delivery systems

Immunostimulatory saponin based colloidal antigen delivery systems show promise as adjuvants for subunit vaccines. For this reason, allyl oleanolate was glycosylated at the 3-position using trichloroacetimidate donors to give monodesmodic saponins following deprotection. Bisdesmodic saponins were synthesized by double glycosylation at the 3- and 28-positions of oleanolic acid. When formulated together with cholesterol and phospholipids, ring-like, helical and rod-like nanostructures were formed depending on the saponin concentrations used. As an indication of adjuvant activity, the ability of these formulations, and the saponins by themselves, to induce dendritic cell maturation was measured, but no significant activity was observed.     

Molecular Complexes of Ivy Triterpene Glycosides with Cholesterol

Russian Journal of Bioorganic Chemistry - The paper reports preparation of molecular complexes of cholesterol with dominant triterpene saponins from members of the ivy genus Hedera L. (Araliaceae...     

紫菀根的结构与主要药用成分积累研究

为揭示紫菀根的结构、主要药用成分积累部位和含量,用石蜡切片法研究不同发育阶段根的结构、组织化学法定位三萜皂苷和黄酮类成分的积累部位、HPLC法测定根中紫菀酮、槲皮素和山奈酚的含量。结果表明,紫菀根的初生结构包括表皮、皮层和维管柱。次生结构包括外皮层、皮层和维管组织,其中分泌道位于皮层内侧,数量与韧皮部束一致,随着根的增粗,中央分化出髓部。三萜皂苷成分在韧皮部和皮层内侧积累较多;黄酮类成分积累于皮层和髓部。紫菀根下部的紫菀酮含量高于上部,槲皮素和山萘酚仅为上部的1/3。因此,建议加工时保留下部细根,实现资源综合利用。     

北柴胡营养器官中主要化学成分的组织化学定位及其含量比较

应用植物解剖学、组织化学定位和植物化学方法,研究了北柴胡各营养器官中柴胡皂苷和黄酮类化合物的积累分布状态及其含量变化。结果表明,柴胡皂苷在根中分布在中柱鞘和次生韧皮部中;在茎中主要分布在表皮、棱角处的厚角组织以及位于皮层和髓中的分泌道的上皮细胞中;在叶中,则分布在表皮细胞和整个叶肉组织中。而黄酮类化合物在茎中分布在表皮、棱角处的厚角组织、皮层、髓射线和髓鞘细胞中;在叶中,则主要分布在表皮和位于上下表皮内的厚角组织中。同时,北柴胡中柴胡总皂苷在根、茎、叶中的含量的变化规律为根>叶>茎;而总黄酮在根、茎、叶中的含量的变化规律为叶>茎>根;且在叶中含量相当高,从而为北柴胡的综合利用提供依据,对合理利用药材和保护北柴胡资源也有一定意义。     

Hemolytic mechanism of dioscin proposed by molecular dynamics simulations

Saponins are a class of compounds containing a triterpenoid or steroid core with some attached carbohydrate modules. Many saponins cause hemolysis. However, the hemolytic mechanism of saponins at the molecular level is not yet fully understood. In an attempt to explore this issue, we have studied dioscin—a saponin with high hemolytic activity—through extensive molecular dynamics (MD) simulations. Firstly, all-atom MD simulations of 8 ns duration were conducted to study the stability of the dioscin–cholesterol complex and the cholesterol–cholesterol complex in water and in decane, respectively. MM-GB/SA computations indicate that the dioscin–cholesterol complex is energetically more favorable than the cholesterol–cholesterol complex in a non-polar environment. Next, several coarse-grained MD simulations of 400 ns duration were conducted to directly observe the distribution of multiple dioscin molecules on a DPPC-POPC-PSM-CHOL lipid bilayer. Our results indicate that dioscin can penetrate into the lipid bilayer, accumulate in the lipid raft micro-domain, and then bind cholesterol. This leads to the destabilization of lipid raft and consequent membrane curvature, which may eventually result in the hemolysis of red cells. This possible mechanism of hemolysis can well explain some experimental observations on hemolysis.     

Enhanced triterpene saponin biosynthesis and root nodulation in transgenic barrel medic (Medicago truncatula Gaertn.) expressing a novel β-amyrin synthase (AsOXA1) gene

Triterpene saponins are a group of bioactive compounds abundant in the genus Medicago , and have been studied extensively for their biological and pharmacological properties. In this article, we evaluated the effects of the ectopic expression of AsOXA1 cDNA from Aster sedifolius on the production of triterpene saponins in barrel medic ( Medicago truncatula Gaertn.). AsOXA1 cDNA encodes β-amyrin synthase, a key enzyme involved in triterpene saponin biosynthesis. One of the four transgenic lines expressing AsOXA1 accumulated significantly larger amounts of some triterpenic compounds in leaf and root than did control plants. In particular, the leaf exhibited significantly higher levels of bayogenin, medicagenic acid and zanhic acid. The amounts of medicagenic acid and zanhic acid, which represent the core of the M. truncatula leaf saponins, were 1.7 and 2.1 times higher, respectively, than the amounts extracted from the control line. In root, the production of bayogenin, hederagenin, soyasapogenol E and 2β-hydroxyoleanolic acid was increased significantly. The increase in the total amounts of triterpenic compounds observed in the leaves of transgenic lines correlated with the AsOXA1 expression level. Interestingly, the plants expressing AsOXA1 showed, under different growth conditions, improved nodulation when compared with the control line. Nodulation enhancement was also accompanied by a significant change in the soyasapogenol B content. Our results indicate that the ectopic expression of AsOXA1 in barrel medic leads to a greater accumulation of triterpene saponins and enhanced root nodulation.