A new semisynthetic ocotillol-type saponin and resuscitation of haemorrhagic shock

Discovery, semisynthesis, biological activities, and metabolism of ocotillol-type saponins

Ocotillol-type saponins are one kind of tetracyclic triterpenoids, sharing a tetrahydrofuran ring. Natural ocotillol-type saponins have been discovered in Panax quinquefolius L., Panax japonicus, Hana mina, and Vietnamese ginseng. In recent years, the semisynthesis of 20(S/R)-ocotillol-type saponins has been reported. The biological activities of ocotillol-type saponins include neuroprotective effect, antimyocardial ischemia, antiinflammatory, antibacterial, and antitumor activities. Owing to their chemical structure, pharmacological actions, and the stereoselective activity on antimyocardial ischemia, ocotillol-type saponins are subjected to extensive consideration. In this review, we sum up the discovery, semisynthesis, biological activities, and metabolism of ocotillol-type saponins.

Synthesis of Ocotillol-Type Ginsenosides

A total of 14 ocotillol-type ginsenosides were conveniently synthesized employing glycosylation of ocotillol sapogenin derivatives with glucosyl ortho-alkynylbenzoate donors under the promotion of a gold(I) catalyst as the key step. Relying on a rational protecting group strategy and the unexpected regioselectivity of the glycosylation of the 3,25-diol sapogenins (2a/2b, 5a/5b) for the tertiary 25-OH, mono 3-O-glucosyl ocotillol-PPD, 6-O-glucosyl ocotillol-PPT, 25-O-glucosyl ocotillol-PPD/PPT and 3,25-di-O-glucosyl ocotillol-PPD/PPT ginsenosides were prepared in which the configuration at the C-24 is either R or S.

Synthesis and Crystal Structures of Two C24 Epimeric 3-Acetyled 20(R)-Ocotillol Type Sapogenins Obtained from 20(R)-Protopanaxadiol

Two C24 epimeric 3-acetylated ocotillol-type sapogenins, 20 R,24 S-epoxy-dammarane-3β,12β,25-triol acetate and 20 R,24 R-epoxy-dammarane-3β,12β,25-triol acetate have been achieved from 20( R)-protopanaxadiol. Their structures were confirmed by HRMS, 1H NMR, 13C NMR and single crystal X-ray diffraction which showed that their configurations were (20 R, 24 S) and (20 R, 24 R), respectively. In the crystal structure of the 24 ( S)-epimer, there were two intramolecular hydrogen bonds and a left-handed helical chain whilst in the 24 ( R)-epimer there was one intramolecular hydrogen bond and a right-handed helical chain.

Ginsenoside Rg3 induces FUT4-mediated apoptosis in H. pylori CagA-treated gastric cancer cells by regulating SP1 and HSF1 expressions

Helicobacter pylori (H. pylori) cytotoxin associated antigen A (CagA) plays a significant role in the development of gastric cancer. Ginsenoside Rg3 is a herbal medicine which inhibits cell proliferation and induces apoptosis in various cancer cells. Fucosylation plays important roles in cancer biology as increased fucosylation levels of glycoproteins and glycolipids have been reported in many cancers. Fucosyltransferase IV (FUT4) is an essential enzyme, catalyzes the synthesis of LewisY oligosaccharides and is regulated by specificity protein 1 (SP1) and heat shock factor protein 1 (HSF1) transcription factors. Herein, we studied the mechanism action of Rg3 apoptosis induction in gastric cancer cells. We treated the gastric cancer cells with CagA followed by Rg3, and analyzed their ability to induce apoptosis by evaluating the role of FUT4 as well as SP1 and HSF1 expressions by Western blot, flow cytometry and ELISA. We found that Rg3 significantly induced apoptosis in CagA treated gastric cancer cells, as evidenced by nuclear staining of 4-6-diamidino-2-phenylindole (DAPI) and Annexin-V/PI double-labeling. In addition, Rg3 significantly increased the expression of pro-apoptotic proteins and triggered the activation of caspase-3, -8, and -9 and PARP. Moreover, Rg3-induced apoptotic mechanisms indicated that Rg3 inhibited FUT4 expression through SP1 upregulation and HSF1 downregulation. Hence, Rg3 therapy is an effective strategy for gastric cancer treatment. Furthermore SP1 and HSF1 may serve as potential diagnostic and therapeutic targets for gastric cancer.

Semisynthesis and bioactive evaluation of oxidized products from 20(S)-ginsenoside Rg3, Rh2, protopanaxadiol (PPD) and their 20(R)-epimers as cytotoxic agents

A series of oxidized products have been systematically semisynthesized from 20(S)-ginsenoside Rg3, Rh2, 20(S)-protopanaxadiol (PPD) and their 20(R)-epimers and the majority of these products were evaluated for their cytotoxic activity against HeLa cells and HepG2 cells by MTT assay for the first time. Twenty-two products were obtained and elucidated based on comprehensive (1)H NMR, (13)C NMR, two-dimensional (2D) NMR, and mass spectral data and the results reported in previous literature. All the four ocotillol type saponins (20S,24R(δ86, δ85); 20S,24S(δ87, δ88); 20R,24R(δ86, δ86); 20R,24S(δ86, δ87) were obtained. In addition, eight compounds (3, 8, 9, 10, 15, 16, 19 and 22) with the cyclized side chain were firstly identified. Most of the tested compounds possessed cytotoxicity to a certain degree against the two types of cells which implied these oxidized products could play a certain role on anti-cancer functions of the raw materials in vivo. Meanwhile, the results proved that the configurations at C-20 or C-24 and the number of glycosyl at C-3 have important influence on the cytotoxicity. The products 1, 2, 11-17, 20 and 22 should possess great activities and deserved further investigation as potential cytotoxic agents.

Saponins in the genus Panax L. (Araliaceae): a systematic review of their chemical diversity

The Panax genus is a crucial source of natural medicines that has benefited human health for a long time. Three valuable medicinal herbs, namely Panax ginseng, Panax quinquefolius, and Panax notoginseng, have received considerable interest due to their extensive application in clinical therapy, healthcare products, and as foods and food additives world-wide. Panax species are known to contain abundant levels of saponins, also dubbed ginsenosides, which refer to a series of dammarane or oleanane type triterpenoid glycosides. These saponins exhibit modulatory effects to the central nervous system and beneficial effects to patients suffering from cardiovascular diseases, and also have anti-diabetic and anti-tumor properties. To the end of 2012, at least 289 saponins were reported from eleven different Panax species. This comprehensive review describes the advances in the phytochemistry of the genus Panax for the period 1963-2012, based on the 134 cited references. The reported saponins can be classified into protopanaxadiol, protopanaxatriol, octillol, oleanolic acid, C17 side-chain varied, and miscellaneous subtypes, according to structural differences in sapogenins. The investigational history of Panax is also reviewed, with special attention being paid to the structural features of the six different subtypes, together with their (1)H and (13)C NMR spectroscopic characteristics which are useful for determining their structures and absolute configuration.

Determination of Pseudoginsengenin DQ in rat plasma by UPLC-MS/MS and application of the method in a pharmacokinetic study

Pseudoginsengenin DQ (pseudoginsengenin of diol derivatives quest, PDQ), the product of the oxidative cyclization of protopanaxadiol, exhibits a significant pharmacological effect as an antiarrhythmic agent. A sensitive and rapid analytical method based on ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) was initially developed for the detection of PDQ in rat plasma. Pre-treatment of the sample obtained from the plasma involved a single protein precipitation step, using methanol. PDQ and an internal standard (IS), physcion, were separated on a Waters ACQUITY UPLC BEH C18 analytical column (50mm×2.1mm, 1.7μm) using acetonitrile-0.1% formic acid in water (70:30, v/v) as the mobile phase, at a flow rate of 0.3mL/min. Chromatography of the PDQ and IS was performed within 3min. Detection was performed through positive ion electrospray ionization (ESI(+)) in multiple reaction-monitoring (MRM) mode. The assay was linear over the concentration range of 5-1000ng/mL (r>0.9980). The limit of detection (LOD) and the lower limit of quantification (LLOQ) were 0.5ng/mL and 5.0ng/mL, respectively. The intra- and inter-day deviations (expressed as relative standard deviation, RSD) were ≤9.5% and ≤1.7%, respectively, and the accuracy (expressed as relative error, RE) was in the range of -1.1 to 2.7%. The recoveries of PDQ and IS were 95.2% and 100.7%, respectively, and the matrix effects were satisfactory in all of the biological matrices examined. This fully validated method was successfully applied to the pharmacokinetic study of rats after a single initial intragastric administration of 15mg/kg PDQ. The main pharmacokinetic parameters: Tmax (the time to peak), Cmax (the concentration to peak), and t1/2 (the biological half time) were 4.0±0.0h, 3265.12±700.26ng/mL, 5.97±0.43h, respectively.

Chemical and molecular mechanisms of antioxidants: experimental approaches and model systems

Free radicals derived from oxygen, nitrogen and sulphur molecules in the biological system are highly active to react with other molecules due to their unpaired electrons. These radicals are important part of groups of molecules called reactive oxygen/nitrogen species (ROS/RNS), which are produced during cellular metabolism and functional activities and have important roles in cell signalling, apoptosis, gene expression and ion transportation. However, excessive ROS attack bases in nucleic acids, amino acid side chains in proteins and double bonds in unsaturated fatty acids, and cause oxidative stress, which can damage DNA, RNA, proteins and lipids resulting in an increased risk for cardiovascular disease, cancer, autism and other diseases. Intracellular antioxidant enzymes and intake of dietary antioxidants may help to maintain an adequate antioxidant status in the body. In the past decades, new molecular techniques, cell cultures and animal models have been established to study the effects and mechanisms of antioxidants on ROS. The chemical and molecular approaches have been used to study the mechanism and kinetics of antioxidants and to identify new potent antioxidants. Antioxidants can decrease the oxidative damage directly via reacting with free radicals or indirectly by inhibiting the activity or expression of free radical generating enzymes or enhancing the activity or expression of intracellular antioxidant enzymes. The new chemical and cell-free biological system has been applied in dissecting the molecular action of antioxidants. This review focuses on the research approaches that have been used to study oxidative stress and antioxidants in lipid peroxidation, DNA damage, protein modification as well as enzyme activity, with emphasis on the chemical and cell-free biological system.

Ketamine delays mortality in an experimental model of hemorrhagic shock and subsequent sepsis

BACKGROUND

In previous studies ketamine was reported to improve survival and decrease serum interleukin-6 (IL-6) concentration after sepsis alone and after burn injury followed by sepsis. The aim of this study was to determine whether ketamine alters survival and/or IL-6 after hemorrhagic shock alone or hemorrhagic shock followed by sepsis.

MATERIALS AND METHODS

Rats were subjected to hemorrhagic shock with or without subsequent Gram-negative bacterial sepsis and were either treated with ketamine 5 mg/kg or were not treated. Blood was sampled for IL-6 determination prior to hemorrhage, at the completion of resuscitation, and at 6 and 30 h later. Mortality was recorded for 7 days following hemorrhage or hemorrhage+sepsis.

RESULTS

After hemorrhage+sepsis the time to median mortality was significantly later in the ketamine-treated group (36 h) than in the control group (12 h). At 12h the survival rate of the ketamine-treated group (100%) was significantly higher than in the control group (55%). There were no significant differences between groups with respect to IL-6 or 7-day survival after either hemorrhage+sepsis or hemorrhage alone.

CONCLUSION

Ketamine improved 12h survival and delayed mortality after hemorrhage+sepsis without significantly altering IL-6, and did not alter survival or IL-6 after hemorrhage alone.