Antitumor agents. 261. 20(S)-protopanaxadiol and 20(s)-protopanaxatriol as antiangiogenic agents and total assignment of (1)H NMR spectra

Differential antiangiogenic and anticancer activities of the active metabolites of ginsenoside Rg3

Background

Epimers of ginsenoside Rg3 (Rg3) have a low bioavailability and are prone to deglycosylation, which produces epimers of ginsenoside Rh2 (S-Rh2 and R-Rh2) and protopanaxadiol (S-PPD and R-PPD). The aim of this study was to compare the efficacy and potency of these molecules as anti-cancer agents.

Methods

Crystal violet staining was used to study the anti-proliferatory action of the molecules on a human epithelial breast cancer cell line, MDA-MB-231, and human umbilical vein endothelial cells (HUVEC) and compare their potency. Cell death and cell cycle were studied using flow cytometry and mode of cell death was studied using live cell imaging. Anti-angiogenic effects of the drug were studied using loop formation assay. Molecular docking showed the interaction of these molecules with vascular endothelial growth factor receptor-2 (VEGFR2) and aquaporin (AQP) water channels. VEGF bioassay was used to study the interaction of Rh2 with VEGFR2, in vitro.

Results

HUVEC was the more sensitive cell line to the anti-proliferative effects of S-Rh2, S-PPD and R-PPD. The molecules induced necroptosis/necrosis in MDA-MB-231 and apoptosis in HUVEC. S-Rh2 was the most potent inhibitor of loop formation. In silico molecular docking predicted a good binding score between Rh2 or PPD and the ATP-binding pocket of VEGFR2. VEGF bioassay showed that Rh2 was an allosteric modulator of VEGFR2. In addition, SRh2 and PPD had good binding scores with AQP1 and AQP5, both of which play roles in cell migration and proliferation.

Conclusion

The combination of these molecules might be responsible for the anti-cancer effects observed by Rg3.

Minor protopanaxadiol type sapogenins from the alkali hydrolysate of stems-leaves of Panax notoginseng

Two new protopanaxadiol type sapogenins, (3β,12β)-3,12,20-trihydroxydammar-24-en-26-al (1) and (3β,12β)-3,12,20-trihydroxydammar-24-en-26-oic acid (2), were isolated from the alkali hydrolysate of stems-leaves of Panax notoginseng, along with seven known analogues (3-9). Their structures were elucidated by spectroscopic analyses and single-crystal X-ray diffraction. Compound 2 and the known sapogenins 5-8 displayed weak to moderate inhibition of NO production in LPS-induced RAW264.7 macrophages with IC50 values from 44.5 to 143.6 μM, respectively.

Inclusion complex of 20(S)-protopanaxatriol with modified β-cyclodextrin: Characterization, solubility, and interaction with bovine serum albumin

20(S)-protopanaxatriol (PPT) is one of the ginsenosides isolated from Panax ginseng which have many pharmaceutical activities. However, the poor water solubility of PPT restrict its applications. Herein, a novel bridged-bis-[6-(3,3'-(ethylenedioxy) bis (propylamine))-6-deoxy-β-cyclodextrin] (EDBA-bis-β-CD) was designed and synthesized, and the inclusion complex (IC) of EDBA-bis-β-CD with PPT was successfully prepared in the solid state, and characterized by UV, ¹H NMR, 2D ROESY, FT-IR, XRD and SEM and molecular modelling methods. The continuous variation method analysis indicated that the stoichiometry of the IC was 1:1. UV-vis spectral analysis demonstrated the binding constant K_s was 995.94 M^-1, and the solubility study showed that the solubility of PPT improved 290 times. The interaction of the IC with bovine serum albumin (BSA) was investigated via fluorescence spectroscopy. The results indicated that fluorescence quenching of BSA by IC was static quenching. Thermodynamic studies showed that van der Waals forces and hydrogen bonding play significant roles in interaction. The esterase-like activity of BSA in the presence of IC showed that it reduce the esterase activity of BSA in a competitive manner. Furthermore, molecular docking and molecular dynamics simulations for EDBA-bis-β-CD/PPT and BSA/IC systems were generated to provide information on the stability and the forces in the binding.

Ginseng in vascular dysfunction: A review of therapeutic potentials and molecular mechanisms

Vascular dysfunction can lead to a variety of fatal diseases, including cardiovascular and cerebrovascular diseases, metabolic syndrome, and cancer. Although a large number of studies have reported the therapeutic effects of natural compounds on vascular-related diseases, ginseng is still the focus of research. Ginseng and its active substances have bioactive effects against different diseases with vascular dysfunction. In this review, we summarized the key molecular mechanisms and signaling pathways of ginseng, its different active ingredients or formula in the prevention and treatment of vascular-related diseases, including cardiac-cerebral vascular diseases, hypertension, diabetes complications, and cancer. Moreover, the bidirectional roles of ginseng in promoting or inhibiting angiogenesis have been highlighted. We systematically teased out the relationship between ginseng and vascular dysfunction, which could provide a basis for the clinical application of ginseng in the future.

Inhibitory effects of Paris saponin I, II, Ⅵ and Ⅶ on HUVEC cells through regulation of VEGFR2, PI3K/AKT/mTOR, Src/eNOS, PLCγ/ERK/MERK, and JAK2-STAT3 pathways

Rhizoma Paris is a popular Chinese medicine in clinics. It contains four main saponins which are its major bioactive compounds. These saponins are Paris saponin I, II, VI and VII (PSI, PSII, PSVI and PSVII, respectively). Up to now, the research using HUVEC cells to evaluate the anti-angiogenic activity of four saponins is blank. The purpose of this study was to evaluate the anti-angiogenic properties (also known as angiotoxicity) of the four saponins in Rhizoma Paris on vascular endothelial cells-HUVEC cells, and to investigate the underlying mechanism, which has not been studied before. In this study, MTT assay, Lactate dehydrogenase (LDH) assay, wound healing experiments, transwell cell invasion assay, tubule formation experiment, DAPI staining, AV-PI double staining, and cell cycle analysis were used to determine the effects of Paris saponins. The results showed that, with increases in concentrations of PSI, PSII, PSVI and PSVII, the viability of HUVEC cells decreased significantly. In addition, four saponins dose-dependent enhanced LDH release and inhibited HUVEC cell migration, invasion, and angiogenesis. In terms of mechanism, PSI significantly inhibited protein expression in multiple signaling pathways. In particular, with the VEGF2 as the target, it activate the downstream PI3K / AKT / mTOR, SRC / eNOS, P38, PLCγ / ERK / MERK and JAK2/STAT3 signaling pathways. In conclusion, PSI, PSII, PSVI and PSVII can inhibit endothelial cell proliferation, migration and invasion, block endothelial cell cycle, induce endothelial cell apoptosis, act on protein expression in several anti-angiogenic signaling pathways, and finally inhibit angiogenesis in vitro. This study provides further data support for the clinical application of Paris saponins as antiangiogenic drugs.

Dammarane-type leads panaxadiol and protopanaxadiol for drug discovery: Biological activity and structural modification

Based on the definite therapeutic benefits, such as neuroprotective, cardioprotective, anticancer, anti-diabetic and so on, the Panax genus which contains many valuable plants, including ginseng (Panax ginseng C.A. Meyer), notoginseng (Panax notoginseng) and American ginseng (Panax quinquefolius L.), attracts research focus. Actually, the biological and pharmacological effects of the Panax genus are mainly attributed to the abundant ginsenosides. However, the low membrane permeability and the gastrointestinal tract influence seriously limit the absorption and bioavailability of ginsenosides. The acid or base hydrolysates of ginsenosides, 20 (R,S)-panaxadiol and 20 (R,S)-protopanaxadiol showed improved bioavailability and diverse pharmacological activities. Moreover, relative stable skeletons and active hydroxyl group at C-3 position and other reactive sites are suitable for structural modification to improve biological activities. In this review, the pharmacological activities of panaxadiol, protopanaxadiol and their structurally modified derivatives are comprehensively summarized.

Formulation and Characterization of Novel Dry Suspension and Dry Emulsion of 20(S)-Protopanaxadiol

To improve the absorption of poorly water-soluble 20(S)-protopanaxadiol (20(S)-PPD), novel 20(S)-PPD-loaded redispersible dry suspension and dry emulsion were developed in this study. 20(S)-PPD dry suspension (PPD-DS) was prepared by enabling drug fully dispersed with suspending agent Avicel CL611 and solubilizer Poloxamer 188. 20(S)-PPD dry emulsion (PPD-DE) was prepared by employing oleic acid as oil phase, Cremophor RH-40 as surfactant, and n-butyl alcohol as co-surfactant. Both PPD-DS and PPD-DE were evaluated for their physicochemical characterization after being dispersed in distilled water. The in vivo pharmacokinetics was evaluated by UPLC-MS/MS. The droplet size of PPD-DS and PPD-DE was in the scope of 1446-1653 nm and 652.8-784.5 nm. The sedimentation volume ratios of PPD-DS and PPD-DE were both at value of 1. The zeta potential of PPD-DS and PPD-DE were from - 53.7 to - 70.4 mV and - 27.5 to - 34.5 mV, respectively, which indicated stable systems. PPD-DS and PPD-DE both achieved dramatically enhanced aqueous solubility and higher perfusion of 20(S)-PPD in rats' intestine. Although statistically, no oral bioavailability enhancements of 20(S)-PPD were achieved in PPD-DE and PPD-DS, there were some improvements in the pharmacokinetic behaviors. Especially, PPD-DS could be a promising drug delivery carrier for 20(S)-PPD with the advantages of long-term stability, dosing flexibility, and the convenience of administering to infants and to those who have difficulty swallowing tablets or capsules.

Production of ginsenoside aglycone (protopanaxatriol) and male sterility of transgenic tobacco co-overexpressing three Panax ginseng genes: PgDDS, CYP716A47, and CYP716A53v2

Background

Protopanaxatriol (PPT) is an aglycone of ginsenosides, which has high medicinal values. Production of PPT from natural ginseng plants requires artificial deglycosylation procedures of ginsenosides via enzymatic or physicochemical treatments. Metabolic engineering could be an efficient technology for production of ginsenoside sapogenin. For PPT biosynthesis in Panax ginseng, damarenediol-II synthase (PgDDS) and two cytochrome P450 enzymes (CYP716A47 and CYP716A53v2) are essentially required.

Methods

Transgenic tobacco co-overexpressing P. ginseng PgDDS, CYP716A47, and CYP716A53v2 was constructed via Agrobacterium-mediated transformation.

Results

Expression of the three introduced genes in transgenic tobacco lines was confirmed by Reverse transcription-polymerase chain reaction (RT-PCR). Analysis of liquid chromatography showed three new peaks, dammarenediol-II (DD), protopanaxadiol (PPD), and PPT, in leaves of transgenic tobacco. Transgenic tobacco (line 6) contained 2.8 μg/g dry weight (DW), 7.3 μg/g DW, and 11.6 μg/g DW of PPT, PPD, and DD in leaves, respectively. Production of PPT was achieved via cell suspension culture and was highly affected by auxin treatment. The content of PPT in cell suspension was increased 37.25-fold compared with that of leaves of the transgenic tobacco. Transgenic tobacco was not able to set seeds because of microspore degeneration in anthers. Transmission electron microscopy analysis revealed that cells of phloem tissue situated in the center of the anther showed an abnormally condensed nuclei and degenerated mitochondria.

Conclusion

We successfully achieved the production of PPT in transgenic tobacco. The possible factors deriving male sterility in transgenic tobacco are discussed.

Transcriptome analysis of 1- and 3-year-old Panax notoginseng roots and functional characterization of saponin biosynthetic genes DS and CYP716A47-like

MAIN CONCLUSION

Transcriptome analysis revealed high expression of saponin biosynthetic genes may account for highly accumulated saponins in 3-year-old Panax notoginseng roots and DS and CYP716A47 - like were functionally verified by transgenic tobacco. Panax notoginseng is a well-known traditional medical herb that contains bioactive compounds known as saponins. Three major dammarene-type triterpene saponins including R1, Rb1, and Rg1 were found to be highly accumulated in the roots of 3-year-old plants when compared to those of 1-year-old plants. However, the underlying cellular mechanism is poorly understood. In this study, transcriptome analysis revealed that most genes involved in saponin biosynthesis in P. notoginseng roots augmented during their growth periods. The analysis of the KEGG pathway indicated that the primary metabolism, cell growth, and differentiation were less active in the roots of 3-year-old plant; however, secondary metabolisms were enhanced, thus providing molecular evidence for the harvesting of P. notoginseng roots in the 3rd year of growth. Furthermore, the functional role of DS and CYP716A47-like, two of the candidate genes involved in saponin biosynthesis isolated from P. notoginseng, were verified via overexpression in cultivated tobacco. Approximately, 0.325 µg g-1 of dammarenediol-II and 0.320 µg g-1 of protopanaxadiol were recorded in the dry leaves of transgenic tobacco overexpressed with DS and both DS and CYP716A47-like, respectively. This study provides insights into the molecular mechanisms for saponin accumulation in P. notoginseng roots during its growth period and paves a promising way to produce dammarenediol-II and protopanaxadiol via transgenic techniques.

20(S)-Protopanaxadiol enhances angiogenesis via HIF-1α-mediated VEGF secretion by activating p70S6 kinase and benefits wound healing in genetically diabetic mice

Impaired angiogenesis is one of the crucial factors that impede the wound healing process in diabetic foot ulcers (DFUs). In this study, we found that 20(S)-protopanaxadiol (PPD), an aglycone of ginsenosides in Panax notoginseng, stimulated angiogenesis and benefited wound healing in genetically diabetic mice. In HUVECs, PPD promoted cell proliferation, tube formation and VEGF secretion accompanied by increased nuclear translocalization of HIF-1α, which led to elevated VEGF mRNA expression. PPD activated both PI3K/Akt/mTOR and Raf/MEK/ERK signaling pathways in HUVECs, which were abrogated by LY294002 and PD98059. Furthermore, these two pathways had crosstalk through p70S6K, as LY294002, PD98059 and p70S6K siRNA abolished the angiogenic responses of PPD. In the excisional wound splinting model established in db/db diabetic mice, PPD (0.6, 6 and 60 mg ml⁻¹) accelerated wound closure, which was reflected by a significantly reduced wound area and epithelial gaps, as well as elevated VEGF expression and capillary formation. In addition, PPD activated PI3K/Akt/ERK signaling pathways, as well as enhanced p70S6K activity and HIF-1α synthesis in the wounds. Overall, our results revealed that PPD stimulated angiogenesis via HIF-1α-mediated VEGF expression by activating p70S6K through PI3K/Akt/mTOR and Raf/MEK/ERK signaling cascades, which suggests that the compound has potential use in wound healing therapy in patients suffering from DFUs.

Endothelium-independent vasorelaxant effect of 20(S)-protopanaxadiol on isolated rat thoracic aorta

AIM

Ginsenosides are considered to be the major pharmacologically active ginseng constituents, whereas 20(S)-protopanaxadiol [20(S)-PPD] is the active metabolite of ginsenosides in gut. In this study we investigated the effect of 20(S)-PPD on isolated rat thoracic aortas as well as its vasorelaxant mechanisms.

METHODS

Aortic rings with or without endothelium were prepared from Wistar rats and suspended in organ-chambers. The changes in tension of the preparations were recorded through isometric transducers connected to a data acquisition system. The aortic rings were precontracted with phenylephrine (PE, 1 μmol/L) or high-K⁺ (80 mmol/L).

RESULTS

Application of 20(S)-PPD (21.5-108.5 μmol/L) caused concentration-dependent vasodilation of endothelium-intact aortic rings precontracted with PE or high-K⁺, which resulted in the EC₅₀ values of 90.4 or 46.5 μmol/L, respectively. The removal of endothelium had no effect on 20(S)-PPD-induced relaxation. The vasorelaxant effect of 20(S)-PPD was also not influenced by the preincubation with β-adrenergic receptor antagonist propranolol, or with ATP-sensitive K⁺ channel blocker glibenclamide, voltage-dependent K⁺ channel blocker 4-AP and inward rectifier K⁺ channel blocker BaCl₂, whereas it was significantly attenuated by the preincubation with Ca²⁺-activated K⁺ (BK_Ca) channel blocker TEA (1 mmol/L). Furthermore, the inhibition of NO synthesis, cGMP and prostacyclin pathways did not affect the vasorelaxant effect of 20(S)-PPD. In Ca²⁺-free solution, 20(S)-PPD (108.5 μmol/L) markedly decreased the extracellular Ca²⁺-induced contraction in aortic rings precontracted with PE or high-K⁺ and reduced PE-induced transient contraction. Voltage-dependent Ca²⁺ channel antagonist nifedipine inhibited PE-induced contraction; further inhibition was observed after the application of receptor-operated Ca²⁺ channel inhibitor SK&F 96365 or 20(S)-PPD.

CONCLUSION

20(S)-PPD induces vasorelaxation via an endothelium-independent pathway. The inhibition of voltage-dependent Ca²⁺ channels and receptor-operated Ca²⁺ channels and the activation of Ca²⁺-activated K⁺ channels are probably involved in the relaxation.

Anticancer Activities of Protopanaxadiol- and Protopanaxatriol-Type Ginsenosides and Their Metabolites

Recently, most anticancer drugs are derived from natural resources such as marine, microbial, and botanical sources, but the low success rates of chemotherapies and the development of multidrug resistance emphasize the importance of discovering new compounds that are both safe and effective against cancer. Ginseng types, including Asian ginseng, American ginseng, and notoginseng, have been used traditionally to treat various diseases, due to their immunomodulatory, neuroprotective, antioxidative, and antitumor activities. Accumulating reports have shown that ginsenosides, the major active component of ginseng, were helpful for tumor treatment. 20(S)-Protopanaxadiol (PDS) and 20(S)-protopanaxatriol saponins (PTS) are two characteristic types of triterpenoid saponins in ginsenosides. PTS holds capacity to interfere with crucial metabolism, while PDS could affect cell cycle distribution and prodeath signaling. This review aims at providing an overview of PTS and PDS, as well as their metabolites, regarding their different anticancer effects with the proposal that these compounds might be potent additions to the current chemotherapeutic strategy against cancer.

Chemical transformation of ginsenoside Re by a heteropoly acid investigated using HPLC-MSn/HRMS

The mechanism and pathway of heteropoly acid-derived chemical transformation of ginsenoside Re are investigated using multistage tandem mass spectrometry and high-resolution mass spectrometry.

Conformational studies of dammarane-type triterpenoids using computational and NMR spectroscopic methods

Natural triterpenoids are of great interest to researchers of various fields as they possess diverse physicochemical and biological properties. In medicinal chemistry, detailed information about the chemical structures of bioactive triterpenoids often helps find new lead compounds. Herein, the low-energy structures of (20S)-protopanaxadiol and (20S)-protopanaxatriol, the aglycones of various triterpenoid saponins found in Panax ginseng, and their (20R)-epimers have been predicted by the geometry optimization of the conformers extracted from molecular dynamics simulations with the self-consistent-charge density functional tight-binding method. By performing quantum mechanical calculations on the low-energy conformers, we have estimated the NMR chemical shifts of the compounds, which display good agreement with the most recently reported experimental values within an expected range of errors. Our results indicate that theoretical estimation of the NMR parameters of a relatively large molecule with a molecular mass of 500 is feasible.

Recent advances in ginseng as cancer therapeutics: a functional and mechanistic overview

Cancer is one of the leading causes of death worldwide. Ginseng, a key ingredient in traditional Chinese medicine, shows great promise as a new treatment option. As listed by the U.S. National Institutes of Health as a complementary and alternative medicine, its anti-cancer functions are being increasingly recognized. This review covers the mechanisms of action of ginsenosides and their metabolites, which can modulate signaling pathways associated with inflammation, oxidative stress, angiogenesis, metastasis, and stem/progenitor-like properties of cancer cells. The emerging use of structurally modified ginsenosides and recent clinical studies on the use of ginseng either alone or in combination with other herbs or Western medicines which are exploited as novel therapeutic strategies will also be explored.

A nanoparticulate drug-delivery system for 20(S)-protopanaxadiol: formulation, characterization, increased oral bioavailability and anti-tumor efficacy

As with many other hydrophobic anticancer agents, 20(S)-protopanaxadiol (PPD) has a very low oral bioavailability. In this study, a precipitation-combined ultrasonication technique was used to prepare PPD nanosuspensions. The mean particle size of the nanosuspensions was approximately 222 ± 12 nm, the drug payload achieved 50% after lyophilization and the maximum PPD concentration can reach 100 mg/ml, which is over 30 000 times the solubility of PPD in aqueous solution (3 μg/ml). After oral administration, the C_max and AUC_last values of PPD nanosuspensions were approximately 3.66-fold and 3.48-fold as those of PPD coarse suspensions, respectively. In contrast to the free drug solution, PPD nanosuspensions showed higher in vitro anti-tumor activity against HepG-2 cells (an IC₅₀ value of 1.40 versus 5.83 μg/ml at 24 h, p < 0.01). The in vivo study in H22-tumor-bearing mice demonstrated that PPD nanosuspensions showed good anti-tumor efficacy with an inhibition rate of 79.47% at 100 mg/kg, while 50 mg/kg of cyclophosphamide was displayed as positive control, and the inhibition rate was 87.81%. Considering the highest drug payload, oral bioavailability reported so far, significant anti-tumor efficacy and excellent safety of encapsulated drugs, PPD nanosuspensions could be used in potential effective strategies for anticancer therapy; further investigation is ongoing.

Pro-angiogenic activity of notoginsenoside R1 in human umbilical vein endothelial cells in vitro and in a chemical-induced blood vessel loss model of zebrafish in vivo

OBJECTIVE

This study aimed at investigating whether notoginsenoside R1 (R1), a unique saponin found in Panax notoginseng could promote angiogenic activity on human umbilical vein endothelial cells (HUVECs) and elucidate their potential molecular mechanisms. In addition, vascular restorative activities of R1 was assessed in a chemically-induced blood vessel loss model in zebrafish.

METHODS

The in vitro angiogenic effect of R1 was compared with other previously reported angiogenic saponins Rg1 and Re. The HUVECs proliferation in the presence of R1 was determined by cell proliferation kit II (XTT) assay. R1, Rg1 and Re-induced HUVECs invasion across polycarbonate membrane was stained with Hoechst-33342 and quantified microscopically. Tube formation assay using matrigelcoated wells was performed to evaluate the pro-angiogenic actions of R1. In order to understand the mechanism underlying the pro-angiogenic effect, various pathway inhibitors such as SU5416, wortmannin (wort) or L-Nω-nitro- L-arginine methyl ester hydrochloride (L-NAME), SH-6 were used to probe the possible involvement of signaling pathway in the R1 mediated HUVECs proliferation. In in vivo assays, zebrafish embryos at 21 hpf were pre-treated with vascular endothelial growth factor (VEGF) receptor kinase inhibitor II (VRI) for 3 h only and subsequently post-treated with R1 for 48 h, respectively. The intersegmental vessels (ISVs) in zebrafish were assessed for the restorative effect of R1 on defective blood vessels.

RESULTS

R1 could stimulate the proliferation of HUVECs. In the chemoinvasion assay, R1 significantly increased the number of cross-membrane HUVECs. In addition, R1 markedly enhanced the tube formation ability of HUVECs. The proliferative effects of these saponins on HUVECs were effectively blocked by the addition of SU5416 (a VEGF-KDR/Flk-1 inhibitor). Similarly, pre-treatment with wort [a phosphatidylinositol 3-kinase (PI3K)-kinase inhibitor], L-NAME [an endothelial nitric oxide synthase (eNOS) inhibitor] or SH-6 (an Akt pathway inhibitor) significantly abrogated the R1 induced proliferation of HUVECs. In chemicallyinduced blood vessel loss model in zebrafish, R1 significantly rescue the damaged ISVs.

CONCLUSION

R1, similar to Rg1 and Re, had been showed pro-angiogenic action, possibly via the activation of the VEGF-KDR/Flk-1 and PI3K-Akt-eNOS signaling pathways. Our findings also shed light on intriguing pro-angiogenic effect of R1 under deficient angiogenesis condition in a pharmacologic-induced blood vessels loss model in zebrafish. The present study in vivo and in vitro provided scientific evidence to explain the ethnomedical use of Panax notoginseng in the treatment of cardiovascular diseases, traumatic injuries and wound healing.

Dammarane triterpenes from the leaves of Panax ginseng enhance cellular immunity

In our search for immune stimulating materials from natural source, bioassay-guided fractionation of a methanol extract of Panax ginseng leaves led to the isolation of three dammarane triterpenes (1-3), including two previously unknown compounds 27-demethyl-(E,E)-20(22),23-dien-3β,6α,12β-trihydroxydammar-25-one (1) and 3β,20(S)-dihydroxydammar-24-en-12β,23β-epoxy-20-O-β-D-glucopyranoside (2). Their structures were elucidated on the basis of spectroscopic methods, chemical transformation, and by the comparison with those of literature data. Compounds 1-3 significantly increased interleukin-12 expression in LPS-activated mouse peritoneal macrophage at a concentration of 100 ng/mL. Furthermore, compound 1 strongly increased the Th1 response-mediated cytokine IL-2, and decreased Th2 response-mediated cytokines IL-4 and IL-6 expression at 100 ng/mL on ConA-activated splenocytes. This study indicated that compound 1 showed a better effect on cellular immunity, and provided new chemical entities as promising lead compounds for the treatment of cellular immunity-related diseases.

Chemical Diversity of Panax ginseng, Panax quinquifolium, and Panax notoginseng

The major commercial ginsengs are Panax ginseng Meyer (Korean ginseng), P. quinquifolium L. (American ginseng), and P. notoginseng (Burk.) FH Chen (Notoginseng). P. ginseng is the most commonly used as an adaptogenic agent and has been shown to enhance physical performance, promote vitality, increase resistance to stress and aging, and have immunomodulatory activity. These ginsengs contain saponins, which can be classified as dammarane-type, ocotillol-type and oleanane-type oligoglycosides, and polysaccharides as main constituents. Dammarane ginsenosides are transformed into compounds such as the ginsenosides Rg3, Rg5, and Rk1 by steaming and heating and are metabolized into metabolites such as compound K, ginsenoside Rh1, protoand panaxatriol by intestinal microflora. These metabolites are nonpolar, pharmacologically active and easily absorbed from the gastrointestinal tract. However, the activities metabolizing these constituents into bioactive compounds differ significantly among individuals because all individuals possess characteristic indigenous strains of intestinal bacteria. To overcome this difference, ginsengs fermented with enzymes or microbes have been developed.

Characterization of metabolites of 20(S)-protopanaxadiol in rats using ultra-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry

In this study, ultra-performance liquid chromatography (UPLC)/quadrupole-time-of-flight mass spectrometry (QTOF-MS) was applied to the rapid analysis of 20(S)-protopanaxadiol (PPD) metabolites in rats after oral administration, enabling the structural characterization of 23 metabolites in plasma, bile, urine, and feces. 16 of these, including M1-M5, M9, and M11-M15, have not been previously reported. The results also indicated that demethylation, dehydration, dehydrogenation, oxidation, deoxidation, and glucuronidation were the major metabolic reactions of PPD in vivo. This study provides important information about the metabolism of PPD which will be helpful for fully understanding its mechanism of action. Furthermore, structural modification of PPD in vivo may aid in obtaining new chemical derivatives for pharmacological screening.

Enhanced oral absorption of 20(S)-protopanaxadiol by self-assembled liquid crystalline nanoparticles containing piperine: in vitro and in vivo studies

Background

20(S)-protopanaxadiol (PPD), similar to several other anticancer agents, has low oral absorption and is extensively metabolized. These factors limit the use of PPD for treatment of human diseases.

Methods

In this study, we used cubic nanoparticles containing piperine to improve the oral bioavailability of PPD and to enhance its absorption and inhibit its metabolism. Cubic nanoparticles loaded with PPD and piperine were prepared by fragmentation of glyceryl monoolein (GMO)/poloxamer 407 bulk cubic gel and verified using transmission electron microscopy and differential scanning calorimetry. We evaluated the in vitro release of PPD from these nanoparticles and its absorption across the Caco-2 cell monolayer model, and subsequently, we examined the bioavailability and metabolism of PPD and its nanoparticles in vivo.

Results

The in vitro release of PPD from these nanoparticles was less than 5% at 12 hours. PPD-cubosome and PPD-cubosome loaded with piperine (molar ratio PPD/piperine, 1:3) increased the apical to basolateral permeability values of PPD across the Caco-2 cell monolayer from 53% to 64%, respectively. In addition, the results of a pharmacokinetic study in rats showed that the relative bioavailabilities of PPD-cubosome [area under concentration–time curve (AUC)_0–∞] and PPD-cubosome containing piperine (AUC_0–∞) compared to that of raw PPD (AUC_0–∞) were 166% and 248%, respectively.

Conclusion

The increased bioavailability of PPD-cubosome loaded with piperine is due to an increase in absorption and inhibition of metabolism of PPD by cubic nanoparticles containing piperine rather than because of improved release of PPD. The cubic nanoparticles containing piperine may be a promising oral carrier for anticancer drugs with poor oral absorption and that undergo extensive metabolism by cytochrome P450.

Acylated protopanaxadiol-type ginsenosides from the root of Panax ginseng

Six new protopanaxadiol-type ginsenosides, named ginsenosides Ra(4) -Ra(9) (1-6, resp.), along with 14 known dammarane-type triterpene saponins, were isolated from the root of Panax ginseng, one of the most important Chinese medicinal herbs. The structures of the new compounds were determined by spectroscopic methods, including 1D- and 2D-NMR, HR-MS, and chemical transformation as (20S)- 3-O-{β-D-6-O-[(E)-but-2-enoyl]glucopyranosyl-(1→2)-β-D-glucopyranosyl}-20-O-[β-D-xylopyranosyl-(1→4)-α-L-arabinopyranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (1), (20S)-3-O-[β-D-6-O-acetylglucopyranosyl-(1→2)-β-D-glucopyranosyl]-20-O-[β-D-xylopyranosyl-(1→4)-α-L-arabinopyranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (2), (20S)-3-O-{β-D-6-O-[(E)-but-2-enoyl]glucopyranosyl-(1→2)-β-D-glucopyranosyl}-20-O-[β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (3), (20S)-3-O-{β-D-6-O-[(E)-but-2-enoyl]glucopyranosyl-(1→2)-β-D-glucopyranosyl}-20-O-[α-L-arabinopyranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (4), (20S)-3-O-{β-D-4-O-[(E)-but-2-enoyl]glucopyranosyl-(1→2)-β-D-glucopyranosyl}-20-O-[α-L-arabinofuranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (5), (20S)-3-O-{β-D-6-O-[(E)-but-2-enoyl]glucopyranosyl-(1→2)-β-D-glucopyranosyl}-20-O-[α-L-arabinofuranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (6). The sugar moiety at C(3) of the aglycone of each new ginsenoside is butenoylated or acetylated.

Dammarenediol-II production confers TMV tolerance in transgenic tobacco expressing Panax ginseng dammarenediol-II synthase

Panax ginseng is one of the famous medicinal plants. Ginsenosides, a class of tetracyclic triterpene saponins, are mainly responsible for its pharmacological activity. Most ginsenosides are composed of dammarenediol-II aglycone with various sugar moieties. Dammarenediol-II synthase is the first enzyme in the biosynthesis of ginsenosides. Here, we report that transgenic tobacco expressing the P. ginseng dammarenediol-II synthase gene (PgDDS) produced dammarenediol-II, and conferred resistance to Tobacco mosaic virus (TMV). Upon infection with TMV, lesions developed more rapidly in transgenic tobacco plants, and their size was smaller than those of wild-type plants. Transgenic tobacco plants showed a low level of both the viral titer and mRNA accumulation of TMV coat protein (CP) compared with the wild type. The production of dammarenediol-II in transgenic tobacco stimulated the expression of tobacco pathogenesis-related genes (PR1 and PR2) under both virus-untreated and -treated conditions. When the leaves of wild-type plants were inoculated with a mixture of TMV and dammarenediol-II, the leaves exhibited a reduced viral concentration and TMV-CP expression than those receiving TMV treatment alone. When the leaves of P. ginseng were infected with TMV, transcription of PgDDS was significantly increased. Transgenic P. ginseng plants harboring a β-glucuronidase (GUS) gene driven by the PgDDS promoter were constructed. The GUS expression was activated when the transgenic ginseng plants were treated with TMV. These results indicate that the medicinally important dammarenediol-II can be ectopically produced in tobacco, and the production of dammarenediol-II in tobacco plants allows them to adopt a viral defense system.

The in vitro structure-related anti-cancer activity of ginsenosides and their derivatives

Panax ginseng has long been used in Asia as a herbal medicine for the prevention and treatment of various diseases, including cancer. The current study evaluated the cytotoxic potency against a variety of cancer cells by using ginseng ethanol extracts (RSE), protopanaxadiol (PPD)-type, protopanaxatriol (PPT)-type ginsenosides fractions, and their hydrolysates, which were prepared by stepwise hydrolysis of the sugar moieties of the ginsenosides. The results showed that the cytotoxic potency of the hydrolysates of RSE and total PPD-type or PPT-type ginsenoside fractions was much stronger than the original RSE and ginsenosides; especially the hydrolysate of PPD-type ginsenoside fractions. Subsequently, two derivatives of protopanaxadiol (1), compounds 2 and 3, were synthesized via hydrogenation and dehydration reactions of compound 1. Using those two derivatives and the original ginsenosides, a comparative study on various cancer cell lines was conducted; the results demonstrated that the cytotoxic potency was generally in the descending order of compound 3 > 20(S)-dihydroprotopanaxadiol (2) > PPD (1) > 20(S)-Rh2 > 20(R)-Rh2 ≈ 20(R)-Rg3 ≈ 20(S)-Rg3. The results clearly indicate the structure-related activities in which the compound with less polar chemical structures possesses higher cytotoxic activity towards cancer cells.

Dammarane-type saponins from steamed leaves of Panax Notoginseng

Four new dammarane-type triterpenoid saponins, namely notoginsenosides SFt₁-SFt₄ (1–4) were isolated from the steamed leaves of Panax notoginseng (Burk.) F. H. Chen (Araliaceae), together with 17 known saponins. Their structures were established on the basis of detailed spectroscopic analyses and acidic hydrolysis. The known ginsenosides Rk2 and Rh3 were obtained from P. notoginseng for the first time. All of these new saponins showed no in vitro cytotoxicity against five human cancer cell lines (HL-60, SMMC-7712, A-549, MCF-7, and SW480).

20(S)-Protopanaxadiol, a metabolite of ginsenosides, induced cell apoptosis through endoplasmic reticulum stress in human hepatocarcinoma HepG2 cells

20(S)-Protopanaxadiol (PPD), a metabolite of ginsenosides, has been demonstrated to possess cytotoxic effects on several cancer cell lines. The molecular mechanism is, however, not well understood. In this study, we have shown that PPD inhibits cell growth and induces apoptosis in human hepatocarcinoma HepG2 cells. PPD-treated cells showed a massive cytoplasmic vacuolization and a dramatic change of endoplasmic reticulum (ER) morphology. The induction of ER stress is associated with the upregulation of ER stress-associated genes and proteins. PPD activates the unfolded protein response (UPR) through the phosphorylation of PERK and eIF2α, the splicing of XBP1 mRNA, and the cleavage of AFT6. PPD also induces the intrinsic and extrinsic apoptotic pathways. It activates DR5, caspase-8, -9, -3, and promotes the cleavage of PARP while it downregulates Bcl-2, Bcl-x(L) and mitochondrial membrane potential. Knockdown of one of the three UPR limbs by specific siRNAs did not affect PPD-induced apoptosis, which was however, significantly suppressed by the downregulation of CHOP. Western blot analysis showed that PPD-stimulated downregulation of Bcl-2 protein, increase of DR5 protein, activation of caspase-8 and cleavage of PARP were significantly inhibited in CHOP siRNA-transfected cells. Taken together, we have identified ER as a molecular target of PPD and our data support the hypothesis that PPD induces HepG2 cell apoptosis through the ER stress pathway.

Synthesis of protopanaxadiol derivatives and evaluation of their anticancer activities

Protopanaxadiol (PPD), an aglycon of ginseng saponins, has shown anticancer activity in earlier studies. Here, we have reported the semisynthesis of nine PPD derivatives with acetyl substitutions. Subsequently, the antiproliferative effects of these nine analogs on different human cancer cell lines have been investigated. Compounds 1, 3, and 5 showed more significant and more potent antiproliferative activity compared with PPD and other derivatives. A flow cytometric assay indicated that compounds 1, 3, and 5 arrested cell cycle progression in the G1 phase and significantly induced apoptosis of cancer cells.

Identification of 20(S)-protopanaxadiol metabolites in human liver microsomes and human hepatocytes

20(S)-Protopanaxadiol (PPD, 1) is one of the aglycones of the ginsenosides and has a wide range of pharmacological activities. At present, PPD has progressed to early clinical trials as an antidepressant. In this study, its fate in mixed human liver microsomes (HLMs) and human hepatocytes was examined for the first time. By using liquid chromatography-electrospray ionization ion trap mass spectrometry, 24 metabolites were found. Four metabolites were isolated, and their structures were elucidated as (20S,24S)-epoxydammarane-3,12,25-triol (2), (20S,24R)-epoxydammarane-3,12,25-triol (3), (20S,24S)-epoxydammarane-12,25-diol-3-one (4), and (20S,24R)-epoxydammarane-12,25-diol-3-one (5) based on a detailed analysis of their spectroscopic data. The predominant metabolic pathway of PPD observed was the oxidation of the 24,25-double bond to yield 24,25-epoxides, followed by hydrolysis and rearrangement to form the corresponding 24,25-vicinal diol derivatives (M6) and the 20,24-oxide form (2 and 3). Further sequential metabolites (M2-M5) were also detected through the hydroxylation and dehydrogenation of 2 and 3. All of the phase I metabolites except for M1-1 possess a hydroxyl group at C-25 of the side chain, which was newly formed by biotransformation. Two glucuronide conjugates (M7) attributed to 2 and 3 were detected in human hepatocyte incubations, and their conjugation sites were tentatively assigned to the 25-hydroxyl group. The findings of this study strongly suggested that the formation of the 25-hydroxyl group is very important for the elimination of PPD.

American ginseng: potential structure-function relationship in cancer chemoprevention

Ginseng has a prominent position on the list of best-selling herbal products in the world, and its main active constituents are thought to be ginsenosides. Compared with the long history of use and widespread research on Asian ginseng, studies of American ginseng are relatively limited, especially regarding cancer chemoprevention. In recent studies of American ginseng, steaming or heating altered the ginsenoside profile and thereby increased anticancer effects. Yet the ginsenoside structures and their activities have not been systematically elucidated. In this commentary, we introduce the different ginsenosides in American ginseng, both the naturally occurring compounds and those resulting from steaming or biotransformation. We briefly review American ginseng's reported anticancer effects and their mechanisms of action, and explore the possible structural-function relationship with a focus on sugar molecules, hydroxyl groups and stereoselectivity in ginsenosides. Understanding these relationships may produce insights into chemical and pharmacological approaches for enhancing the chemopreventive effects of ginsenoside and for developing novel anticancer agents.

Characterization of metabolism and in vitro permeability study of notoginsenoside R1 from Radix notoginseng

As a main and characteristic constituent in Radix notoginseng, the fate of notoginsenoside R1 (NGR1) in human is largely unknown. The present study investigated, for the first time, NGR1 metabolism by human intestinal bacteria and liver subcellular fractions, and permeability properties of NGR1 and resultant metabolites on a Caco-2 model. Samples were qualitatively analyzed using HPLC-MS/MS and quantitatively determined using HPLC-UV. When incubated with pooled human intestinal bacteria anaerobically, NGR1 showed biphasic elimination: an insignificant decrease in the first 8 h followed by a rapid elimination during 8-48 h. Four metabolites, three unambiguously identified as ginsenosides Rg1, F1 and 20(S)-protopanaxatriol formed via stepwise deglycosylation, and one tentatively assigned as a dehydrogenated protopanaxatriol with transformation occurring at the tetracyclic triterpenoid skeleton, were produced sequentially. Rg1 and F1 were formed transiently at low apparent velocities, while 20(S)-protopanaxatriol was the major metabolite with a formation rate close to the rate of NGR1 elimination and a low elimination rate. NGR1 remained intact in human liver S9 or microsomes over 1 h. Transport study of NGR1 and its metabolites revealed an ascending permeability order with stepwise deglycosylation. Taken together, the results revealed a determinant role of intestinal bacteria in the overall disposition and potential bioactivity of NGR1 in human.

Chemical constituents from seeds of Panax ginseng: structure of new dammarane-type triterpene ketone, panaxadione, and hplc comparisons of seeds and flesh

A new dammarane-type triterpene ketone, panaxadione, was isolated from the seeds of Panax ginseng C. A. MEYER (Araliaceae) together with two dammarane-type and lupane-type triterpenes, an aromatic oligoglycoside, three sterol glycosides, and three dammarane-type triterpene oligoglycosides (ginsenosides Rd, Re, and Rg(2)). The structure of a new compound was elucidated on the basis of physicochemical evidence. The relative contents of major ginsenosides in the seeds were compared with those of the flesh parts of young and mature fruits.

Determination of 20(S)-ginsenoside Rh1 and its aglycone 20(S)-protopanaxatriol in rat plasma by sensitive LC-APCI-MS method and its application to pharmacokinetic study

Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) method has been developed for the measurement of the concentrations of 20(S)-ginsenoside Rh1 and its aglycone 20(S)-protopanaxatriol in rat plasma with panaxatriol as internal standard. The method involved single liquid-liquid extraction of both 20(S)-ginsenoside Rh1 and 20(S)-protopanaxatriol from plasma samples with n-butanol. The limit of quantification (LOQ) was 5 ng mL(-1) for both compounds. The method was validated within the linear range 5-2000 ng.mL(-1) for both compounds. The correlation coefficient for the calibration regression line was 0.999 or better. Intra-day and inter-day accuracy were better than 15%. The method has been successfully used for the pharmacokinetic studies in rats. After intravenous administrations, the mean retention times of 20(S)-ginsenoside Rh1 and 20(S)-protopanaxatriol were 17.1 +/- 2.0 min and 3.46 +/- 0.33 h, respectively.