Synthesis and anti-tumor evaluation of novel 25-hydroxyprotopanaxadiol analogs incorporating natural amino acids

Amino Acid Derivatives of Ginsenoside AD-2 Induce HepG2 Cell Apoptosis by Affecting the Cytoskeleton

AD-2 (20(R)-dammarane-3β, 12β, 20, 25-tetrol, 25-OH-PPD) was structurally modified to introduce additional amino groups, which can better exert its anti-tumor effects in MCF-7, A549, LoVo, HCT-116, HT -29, and U-87 cell lines. We investigated the cellular activity of 15 different AD-2 amino acid derivatives on HepG2 cells and the possible mechanism of action of the superior derivative 6b. An MTT assay was used to detect the cytotoxicity of the derivatives. Western blotting was used to study the signaling pathways. Flow cytometry was used to detect cell apoptosis and ghost pen peptide staining was used to identify the changes in the cytoskeleton. The AD-2 amino acid derivatives have a better cytotoxic effect on the HepG2 cells than AD-2, which may be achieved by promoting the apoptosis of HepG2 cells and influencing the cytoskeleton. The derivative 6b shows obvious anti-HepG2 cells activity through affecting the expression of apoptotic proteins such as MDM2, P-p53, Bcl-2, Bax, Caspase 3, Cleaved Caspase 3, Caspase 8, and NSD2. According to the above findings, the amino acid derivatives of AD-2 may be developed as HepG2 cytotoxic therapeutic drugs.

Insight on structural modification, biological activity, structure-activity relationship of PPD-type ginsenoside derivatives

Ginsenosides, characterized by triterpenoid, are one of the active components of ginseng. Among them, PPD-type ginsenosides have potent and diverse pharmacological activities, while the effective applications and clinical studies are limited by the poor stability, water solubility and oral bioavailability. In this review, we have attempted to demonstrate the structural-activity relationship of chemical modifications on the dammarane-type skeleton and the C-17 side chain, noting that certain structurally modified derivatives exhibit satisfactory pharmacological activity. This review will provide ideas for the design and synthesis of novel PPD derivatives, and valuable help for the further study of PPD derivatives to make it realize clinical application.

Application of Amino Acids in the Structural Modification of Natural Products: A Review

Natural products and their derivatives are important sources for drug discovery; however, they usually have poor solubility and low activity and require structural modification. Amino acids are highly soluble in water and have a wide range of activities. The introduction of amino acids into natural products is expected to improve the performance of these products and minimize their adverse effects. Therefore, this review summarizes the application of amino acids in the structural modification of natural products and provides a theoretical basis for the structural modification of natural products in the future. The articles were divided into six types based on the backbone structures of the natural products, and the related applications of amino acids in the structural modification of natural products were discussed in detail.

Design and synthesis of diosgenin derivatives as apoptosis inducers through mitochondria-related pathways

Diosgenin (DSG) has attracted attention recently as a potential anticancer therapeutic agent due to its profound antitumor activity. To better utilize DSG as an antitumor compound, two series of DSG-amino acid ester derivatives (3a-3g and 7a-7g) were designed and synthesized, and their cytotoxic activities against six human cancer cell lines (K562, T24, MNK45, HepG2, A549, and MCF-7) were evaluated. The results obtained showed that a majority of derivatives exhibited cytotoxic activities against these six human tumor cells. Structure-activity relationship analysis revealed that the introduction of l-tryptophan to the C-3 position of DSG and the C-26 position of derivative 5 was the preferred option for these compounds to display significant cytotoxic activities. Among them, compound 7g exhibited significant cytotoxicity against the K562 cell line (IC₅₀ = 4.41 μM) and was 6.8-fold more potent than diosgenin (IC₅₀ = 30.04 μM). Further cellular mechanism studies in K562 cells elucidated that compound 7g triggered mitochondrial-related apoptosis by increasing the generation of intracellular reactive oxygen species (ROS) and decreasing mitochondrial membrane potential (MMP), which was associated with upregulation of the gene and protein expression levels of Bax, downregulation of the gene and protein expression levels of Bcl-2 and activation of the caspase cascade. The above results suggested that compound 7g might be considered a promising scaffold for further modification of more potent anticancer agents.

Chemical constituents from acid hydrolyzates of Panax quinquefolius total saponins and their inhibition activity to α-glycosidase and protein tyrosine phosphatase 1B

Objective

To investigate the hypoglycemic components from the acid hydrolyzates of Panax quinquefolius total saponins, and screen the active compounds by in vitro inhibitory activities to α-glycosidase enzymes and protein tyrosine phosphatase-1B (PTP1B).

Methods

The hydrolyzates were chromatographed repeatedly over silica gel column, and the structures of the compounds were determined by means of NMR. The in vitro bioassay was performed through the inhibitory effects on α-glucosidase or/and PTP1B.

Results

Eight compounds were isolated, which identified as 20(S)-panaxadiol (1), (20S,24R)-dammarane-20,24-epoxy-3β,6α,12β,25-tetraol (2), 20(R)-dammarane-3β,12β,20,25-tetraol (3), 20(S)-dammarane-3β,6α,12β,20,25-pentol (4), 20(R)-dammarane-3β,12β,20,25-tetrahydroxy-3β-O-β-d-glucopyranoside (5), β-sitosterol (6), oleanolic acid (7) and 20(S)-protopanaxadiol (8). Compound 5 was ginseng triterpenoid isolated from the acid hydrolysates of total saponins from P. quinquefolius for the first time. In this paper, the possible in vitro inhibitory activities were investigated. Compound 5 exhibited significantly inhibitory activity against α-glucosidase, and the IC₅₀ value [(0.22 ± 0.21) µmol/L] was about 43-fold lower than positive control. For the PTP1B inhibition assay, compound 5 indicated the strongest inhibitory effect with IC₅₀ of (5.91 ± 0.38) µmol/L, followed by compound 4 with IC₅₀ of (6.21 ± 0.21) µmol/L, which were all showed competitive inhibitory pattern by using a Lineweaver-Burk plot.

Conclusion

These results supported the potential application of dammaranes from acid hydrolyzates of P. quinquefolius total saponins can be used as ingredients of ancillary anti-diabetic agent or functional factor.

Synthesis and anti-cancer activity studies of dammarane-type triterpenoid derivatives

Two series of novel derivatives of AD-2, an active ginsenoside derived from ginseng were designed and synthesized. Five human cancer cell lines (MGC-803, SGC-7901, A549, MCF-7, PC-3 cells) and one normal ovarian cell IOSE144 were employed to evaluate the anti-proliferative activity. Most of derivatives possessed obvious enhanced activity compared with AD-2. Among them, compound 4c displayed the most excellent activity in all tested cancer cell lines, especially A549 cells with an IC50 value of 1.07 ± 0.05 μM. The underlying mechanism study suggested that 4c induced S-phase arrest and apoptosis in A549 cells. Increasing the level of ROS and inducing collapse of MMP in cells treated with 4c were also proved. Moreover, Western blot analysis showed that the expression level of p53 and p21 were obviously increased. 4c could remarkably up-regulate the expression of cyt c in cytosol, the ratio of Bax to Bcl-2 and activate caspase-3/9/PARP. Besides, the expression level of MDM2 was remarkably decreased. The results indicated that 4c caused apoptosis through the mitochondrial pathway, which ROS generation was probably involved in, and had the potent to serve as anti-proliferative agent.

Non-protein amino acid derivatives of 25-methoxylprotopanaxadiol/25-hydroxyprotopanaxadioland their anti-tumour activity evaluation

As active components of ginseng, 25-methoxylprotopanaxadiol and 25-hydroxyprotopanaxadiol exhibited an ability to inhibit the growth and proliferation or to induce the differentiation and apoptosis of tumour cells. We modified 25-OCH₃-PPD and 25-OH-PPD with non-protein amino acids and a series of derivatives was obtained by chromatographic separation, purification and spectroscopy analysis. Thirteen derivatives of 25-OCH₃-PPD (compounds 1-13) and 12 derivatives of 25-OH-PPD (compounds 14-25) were synthesised. The anti-cancer activities of the derivatives were evaluated on HCT-116 and BGC-823 cell lines by MTT assay. Compound 9 and compound 14 exhibited considerable anti-tumour activity for HCT-116 and BGC-823 cell lines, exhibited higher cytotoxic activity than 25-OCH₃-PPD and 25-OH-PPD. Therefore, these ginsenoside derivatives could be used as potential lead for the development of a new type of anticancer agent.

Anticancer activity and potential mechanisms of 1C, a ginseng saponin derivative, on prostate cancer cells

Background

AD-2 (20(R)-dammarane-3b, 12b, 20, 25-tetrol; 25-OH-PPD) is a ginsenoside and isolated from Panax ginseng, showing anticancer activity against extensive human cancer cell lines. In this study, effects and mechanisms of 1C ((20R)-3b-O-(L-alanyl)-dammarane-12b, 20, 25-triol), a modified version of AD-2, were evaluated for its development as a novel anticancer drug.

Methods

MTT assay was performed to evaluate cell cytotoxic activity. Cell cycle and levels of reactive oxygen species (ROS) were determined using flow cytometry analysis. Western blotting was employed to analyze signaling pathways.

Results

1C concentration-dependently reduces prostate cancer cell viability without affecting normal human gastric epithelial cell line-1 viability. In LNCaP prostate cancer cells, 1C triggered apoptosis via Bcl-2 family-mediated mitochondria pathway, downregulated expression of mouse double minute 2, upregulated expression of p53 and stimulated ROS production. ROS scavenger, N-acetylcysteine, can attenuate 1C-induced apoptosis. 1C also inhibited the proliferation of LNCaP cells through inhibition on Wnt/β-catenin signaling pathway.

Conclusion

1C shows obvious anticancer activity based on inducing cell apoptosis by Bcl-2 family-mediated mitochondria pathway and ROS production, inhibiting Wnt/β-catenin signaling pathway. These findings demonstrate that 1C may provide leads as a potential agent for cancer therapy.

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Ginseng saponin derivative 1C was obtained by structural modification.

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Anticancer activity of 1C is much better than that of the original compound AD-2 on cancer cells.

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1C induces cell apoptosis by Bcl-2 family-mediated mitochondria pathway and ROS production.

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1C inhibits Wnt/β-catenin signaling pathway

Dammarane triterpenoids for pharmaceutical use: a patent review (2005 - 2014)

INTRODUCTION

Dammarane triterpenoids, the main secondary metabolites of Panax ginseng, are very important natural compounds with remarkable biological activity. They could be isolated from the plants of Panax or other genus, as well as through the modifications of certain natural products. This review is a collection of a number of patents (2005 - 2014) that describe the dammarane triterpenoids for therapeutic or preventive uses on numerous common diseases.

AREAS COVERED

In this review, patents from 2005 to 2014 on chemical structures and treatment of different diseases by dammarane triterpenoids have been summarized. The SciFinder and the World Intellectual Property Organisation databases have been used as main sources for the search.

EXPERT OPINION

In the last decade, over 90 patents concerning dammarane derivatives for pharmaceutical have been published. These types of compounds could be used as agents for prevention and treatment of various kinds of diseases, such as cancer, diabetes mellitus and metabolic syndrome, hyperlipidemia, cardiovascular and cerebrovascular disease, aging, neurodegenerative disease, bone disease, liver disease, kidney disease, gastrointestinal disease, depression-type mental illness and skin aging. Rare plants, except for Panax genus, which contain dammarane triterpenoids should be studied extensively. In addition, more dammarane triterpenoids with good biological activity, especially the aglycones possessing novel side chain, should be prepared using chemical modification. Finally, pharmacological effects of dammarane triterpenoids should be further studied.

Inhibition of neuroinflammation by synthetic androstene derivatives incorporating amino acid methyl esters on activated BV-2 microglia

Androstene derivatives incorporating amino acid methyl esters were prepared, and their anti-inflammatory effects were evaluated in lipopolysaccharide (LPS)-activated BV-2 microglial cells. Several compounds exhibited dose-dependent inhibition. The most active compound, methyl ((3S,10R,13S)-3-hydroxy-10,13-dimethyl-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthrene-17-carbonyl)-L-phenylalaninate (10) significantly suppressed LPS-induced expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). Mechanistic studies revealed that compound 10 markedly inhibits phosphorylation of p38 mitogen-activated protein kinases (MAPKs) and subsequent transcription factor (NF-κB) and activator protein-1 (AP-1) activation. Furthermore, compound 10 decreased LPS-activated microglial neurotoxicity in a condition medium/HT-22 neuroblastoma co-culture model. Taken together, these results suggest 10 is a potential lead compound for the development of a novel therapeutic agent for neurodegenerative diseases.

Semi-synthesis and anti-tumor evaluation of novel 25-hydroxyprotopanaxadiol derivatives as apoptosis inducing agents

Among novel 25-OH-PPD derivatives, compounds 3xt and 9xt exhibited the most potent anti-tumor activities and significantly induced DU145 cell apoptosis.

Anti-tumor activity of three novel derivatives of ginsenoside on colorectal cancer cells

25-Hydroxyprotopanaxadiol (25-OH-PPD) is a natural compound isolated from Panax ginseng, and its anti-tumor activity has been studied in previous publication. In the current study, we investigated the anti-tumor activity of three novel derivatives synthesized from 25-OH-PPD, namely (20R)-12β-O-(l-chloracetyl)-dammarane-3β, 20, 25-triol (xl), (20R)-3β-O-(l-alanyl)-dammarane-12β, 20, 25-triol (1c), and (20R)-3β-O-(Boc-l-arginyl)-dammarane-12β, 20, 25-triol (8b). All three compounds significantly inhibited the growths of human colorectal cancer cells, while having lesser effect on the growth of normal primary muscle cells and spleno-lymphocytes. Further mechanistic study demonstrated that these compounds could induce apoptosis by activating the components of caspase-signaling pathways in HCT116 cells, but not in spleno-lymphocytes. Taken together, the results suggested that 25-OH-PPD derivatives exerted promising anti-tumor activity that is specific to human colorectal cancer cells, and may therefore represent a potential chemotherapeutic strategy for the treatment of colorectal cancer.