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

Advances in the chemistry, pharmacological diversity, and metabolism of 20(R)-ginseng saponins

Ginseng has been used as a popular herbal medicine in East Asia for at least two millennia. However, 20(R)-ginseng saponins, one class of important rare ginsenosides, are rare in natural products. 20(R)-ginseng saponins are generally prepared by chemical epimerization and microbial transformation from 20(S)-isomers. The C20 configuration of 20(R)-ginseng saponins are usually determined by 13C NMR and X-ray single-crystal diffraction. 20(R)-ginseng saponins have antitumor, antioxidative, antifatigue, neuroprotective, and osteoclastogenesis inhibitory effects, among others. Owing to the chemical structure and pharmacological and stereoselective properties, 20(R)-ginseng saponins have attracted a great deal of attention in recent years. In this study, the discovery, identification, chemical epimerization, microbial transformation, pharmacological activities, and metabolism of 20(R)-ginseng saponins are summarized.

Crystal structure of (3R,5R,8R,9R,10R,12R,13R,14R)-4,4,8,10,14-pentamethyl-17-((R)-2,6,6-trimethyltetrahydro-2H-pyran-2-yl)hexadecahydro-1H-cyclopenta[a]phenanthrene-3,12-diol, C30H52O3

C30H52O3, orthorhombic, P212121 (no. 19), a = 6.71147(14) Å, b = 16.6565(4) Å, c = 25.0815(6) Å, V = 2803.85(11) Å3, Z = 4, R gt (F) = 0.0405, wR ref (F 2) = 0.1092, T = 293(2) K.

In vitro and in silico evaluation of stereoselective effect of ginsenoside isomers on platelet P2Y12 receptor

BACKGROUND

P2Y₁₂ receptor (P2Y₁₂R) is a newly discovered Gi-coupled ADP receptor that plays critical role in platelet function. Ginsenosides are the main constituents responsible for most of pharmacological actions of ginseng, especially cardio-cerebrovascular protective efficacy that is closely related to the influence on platelet function.

HYPOTHESIS/PURPOSE

To explore stereoselective effect of naturally abundant ginsenoside isomers, including the C-20 epimers of protopanaxadiol (PPD), protopanaxatriol (PPT), and their glycosides Rg2, Rg3, Rh1, Rh2 on P2Y₁₂R in platelets.

STUDY DESIGN/METHODS

Both in vitro assay and in silico molecular docking study were performed to investigate the stereoselective effects.

RESULTS

In vitro assay using washed rat platelets revealed differential effects of ginsenoside isomers on ADP-induced platelet aggregation with the direction and degree of action varying with chemical structures. More to the point, the ginsenoside 20S-Rh2 but not its 20R-epimer was found to be the only one that could significantly promote in vitro platelets aggregation induced by ADP. The correlation analysis demonstrated that ginsenosides may have impact on P2Y₁₂R related platelet functions through a cAMP-dependent pathway. Molecular docking stimulation further indicated that ginsenoside isomers could be potent substrate of P2Y₁₂R with differential protein-ligand interaction that would be responsible for the stereoselective efficacy of C-20 ginsenoside epimers. Hydrogen bonding with Asp266 via the C-20 hydroxyl may provide ginsenosides with promoting effect on ADP-induced platelets aggregation, whereas interactions with Tyr105 could contribute to the promotion of inhibitory efficacy.

CONCLUSION

Ginsenosides are potent P2Y₁₂R substrate with stereoselective effects on P2Y₁₂R-related platelet function, which result from their chemical diversity and are closely related to the different interaction ways as P2Y₁₂R ligand.

Optimization of Ultrasonic-Assisted Extraction and Purification of Zeaxanthin and Lutein in Corn Gluten Meal

Zeaxanthin and lutein have a wide range of pharmacological applications. In this study, we conducted systematic experimental research to optimize antioxidant extraction based on detection, extraction, process amplification, and purification. An ultrasonic-assisted method was used to extract zeaxanthin and lutein with high efficiency from corn gluten meal. Firstly, the effects of solid-liquid ratio, extraction temperature, and ultrasonic extraction time on the extraction of zeaxanthin were investigated in single-factor experiments. The optimization extraction parameters of zeaxanthin and lutein with ethanol solvent were obtained using the response surface methodology (RSM) as follows: liquid–solid ratio of 7.9:1, extraction temperature of 56 °C, and extraction time of 45 min. The total content of zeaxanthin and lutein was 0.501%. The optimum extraction experimental parameters were verified by process amplification, and we confirmed that the parameters of the extraction process optimized using the RSM design are reliable and precise. Zeaxanthin and lutein from crude extract of corn gluten were separated and purified using silica gel column chromatography with the purity of zeaxanthin increasing from 0.28% to 31.5% (about 110 times) and lutein from 0.25% to 16.3% (about 65 times), which could be used for large-scale industrial production of carotenoids.

Integration of Data-Dependent Acquisition (DDA) and Data-Independent High-Definition MSE (HDMSE) for the Comprehensive Profiling and Characterization of Multicomponents from Panax japonicus by UHPLC/IM-QTOF-MS

The complexity of herbal matrix necessitates the development of powerful analytical strategies to enable comprehensive multicomponent characterization. In this work, targeting the multicomponents from Panax japonicus C.A. Meyer, both data dependent acquisition (DDA) and data-independent high-definition MS^E (HDMS^E) in the negative electrospray ionization mode were used to extend the coverage of untargeted metabolites characterization by ultra-high-performance liquid chromatography (UHPLC) coupled to a Vion^TM IM-QTOF (ion-mobility/quadrupole time-of-flight) high-resolution mass spectrometer. Efficient chromatographic separation was achieved by using a BEH Shield RP18 column. Optimized mass-dependent ramp collision energy of DDA enabled more balanced MS/MS fragmentation for mono- to penta-glycosidic ginsenosides. An in-house ginsenoside database containing 504 known ginsenosides and 60 reference compounds was established and incorporated into UNIFI^TM, by which efficient and automated peak annotation was accomplished. By streamlined data processing workflows, we could identify or tentatively characterize 178 saponins from P. japonicus, of which 75 may have not been isolated from the Panax genus. Amongst them, 168 ginsenosides were characterized based on the DDA data, while 10 ones were newly identified from the HDMS^E data, which indicated their complementary role. Conclusively, the in-depth deconvolution and characterization of multicomponents from P. japonicus were achieved, and the approaches we developed can be an example for comprehensive chemical basis elucidation of traditional Chinese medicine (TCM).

Design, Synthesis and Antibacterial Evaluation of 3-Substituted Ocotillol-Type Derivatives

Antibiotic resistance has become a serious global problem that threatens public health. In our previous work, we found that ocotillol-type triterpenoid saponin showed good antibacterial activity. Based on preliminary structure-activity relationship, novel serious C-3 substituted ocotillol-type derivatives 7⁻26 were designed and synthesized. The in vitro antibacterial activity was tested on five bacterial strains (B. subtilis 168, S. aureus RN4220, E. coli DH5α, A. baum ATCC19606 and MRSA USA300) and compared with the tests on contrast. Among these derivatives, C-3 position free hydroxyl substituted compounds 7⁻14, showed good antibacterial activity against Gram-positive bacteria. Furthermore, compound 22 exhibited excellent antibacterial activity with minimum inhibitory concentrations (MIC) values of 2 μg/mL against MRSA USA300 and 4 μg/mL against B. subtilis. The structure-activity relationships of all current ocotillol-type derivatives our team synthesised were summarized. In addition, the prediction of absorption, distribution, metabolism, and excretion (ADME) properties and the study of pharmacophores were also conducted. These results can provide a guide to further design and synthesis works.

Design, synthesis, and discovery of ocotillol-type amide derivatives as orally available modulators of P-glycoprotein-mediated multidrug resistance

Multidrug resistance (MDR) is a major cause of failure in cancer treatment, in which the overexpression of P-glycoprotein (Pgp) plays a crucial role. Herein, a novel class of ocotillol-type amide derivatives has been designed, synthesized, and evaluated for their ability to reverse MDR. The structure-activity relationship of the reversal activity was analyzed. Ten compounds showed promising chemo-reversal ability, among which the 24R-ocotillol-type amide derivative 6c with an N-Boc-hexanoyl unit exhibited the most potency in reversing paclitaxel resistance in KBV cells. Compound 6c could inhibit Pgp-mediated rhodamine123 efflux function via stimulating Pgp-ATPase activity and exhibited high binding affinity with Pgp in molecular docking studies. Importantly, compound 6c enhanced the efficacy of paclitaxel against KBV cancer cell-derived xenograft tumors in nude mice after oral administration. These results indicate that ocotillol-type amide derivatives are promising lead compounds for overcoming MDR in cancer.