O-glycoside sequence of pentacyclic triterpene saponins from Phytolacca bogotensis using HPLC-ESI/multi-stage tandem mass spectrometry

Isolation and Purification of Kudinosides from Kuding Tea by Semi-Preparative HPLC Combined with MCI-GEL Resin

Background:

Kuding tea, a Traditional Chinese drink, has a history of thousands of years in China. Triterpenoid saponins in Kuding tea are regarded as one of the major functional ingredients.

Objective:

The aim of this paper was to establish separation progress for the isolation and purification of five triterpenoid saponins (kudinoside A, C, D, F, G) from Kuding tea.

Methods:

Nine types of resins, including seven macroporous resins and two MCI-GEL resins, were firstly used for purifying triterpenoid saponins by the adsorption and desorption tests. Further dynamic adsorption/desorption experiments were carried out to obtain the optimal parameters for the five targeted saponins. Then the purification of five triterpenoid saponins (kudinoside A, C, D, F, G) was completed by semi-preparative high-performance liquid chromatography (semi-pHPLC).

Results:

As of optimized results, the HP20SS MCI-GEL was selected as the optimal one. The data also showed that 65.24 mg of refined extract including 7.04 mg kudinoside A, 3.52 mg kudinoside C, 4.04 mg kudinoside D, 4.13 mg kudinoside F, and 34.45 mg kudinoside G, could be isolated and purified from 645.90 mg of crude extract in which the content of five saponins was 81.51% and the average recovery reached 69.76%. The final contents of five saponins increased 6.91-fold as compared to the crude extract.

Conclusion:

The established separation progress was highly efficient, making it a potential approach for the large-scale production in the laboratory and providing several markers of triterpenoid saponins for quality control of Kuding tea or its processing products.

Role of Saponins in Plant Defense Against Specialist Herbivores

The diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae) is a very destructive crucifer-specialized pest that has resulted in significant crop losses worldwide. DBM is well attracted to glucosinolates (which act as fingerprints and essential for herbivores in host plant recognition) containing crucifers such as wintercress, Barbarea vulgaris (Brassicaceae) despite poor larval survival on it due to high-to-low concentration of saponins and generally to other plants in the genus Barbarea. B. vulgaris build up resistance against DBM and other herbivorous insects using glucosinulates which are used in plant defense. Aside glucosinolates, Barbarea genus also contains triterpenoid saponins, which are toxic to insects and act as feeding deterrents for plant specialist herbivores (such as DBM). Previous studies have found interesting relationship between the host plant and secondary metabolite contents, which indicate that attraction or resistance to specialist herbivore DBM, is due to higher concentrations of glucosinolates and saponins in younger leaves in contrast to the older leaves of Barbarea genus. As a response to this phenomenon, herbivores as DBM has developed a strategy of defense against these plant biochemicals. Because there is a lack of full knowledge in understanding bioactive molecules (such as saponins) role in plant defense against plant herbivores. Thus, in this review, we discuss the role of secondary plant metabolites in plant defense mechanisms against the specialist herbivores. In the future, trials by plant breeders could aim at transferring these bioactive molecules against herbivore to cash crops.

Comparative Analysis of Saponins from Different Phytolaccaceae Species and Their Antiproliferative Activities

The quality and the efficacy of herbal medicine are of great concern especially with the increase in their global use. Medicinal plants of different species or collected from different geographical regions have shown variations in both their contents and pharmacological activities due to the differences in the environmental conditions of the collected sites. In this study, roots of Phytolacca acinosa found in different provinces in south China (Sichuan and Shandong) and a species of Phytolacca americana were investigated. To ensure a maximum yield of the major compounds, the extraction method and conditions were optimized. The preeminent method of extraction in this analysis was determined to be the ultrasound-assisted method with specific conditions as follows: ethanol-H₂O (1:1, v/v), with a solvent: sample ratio of 1:8, and extraction was performed 3 times, each for 30 min. Under these conditions, samples from the different regions varied both in quantity and quality via the LC-MS analysis. A total of 60 triterpenoid saponins were detected within the three samples, among which 22 were identified as common in the three samples. The amounts of these common triterpenoid saponin identified varied across the samples. Moreover, the analysis led to the detection of some novel compounds that have not yet been reported in this family, while other compounds differ in their fragmentation pathways compared to previous literature. To further divulge the correlations between the bioactivities in these three samples and the quantity and quality of their bioactive components, a cytotoxic analysis was thus carried out with two cancer cell lines, and SGC-7901 and Hep G2, which evidently showed remarkable differences in their anti-proliferative activities with respect to the IC₅₀ value. Samples of P. acinosa from Sichuan showed higher values in both cell lines (27.20 ± 1.60 and 25.59 ± 1.63 µg/mL) compared to those of Shandong and P. americana. For the first time, analysis and comparison of both interspecies and of different species in this family were carried out. This study will significantly contribute to the quality insurance of herbal medicine, especially in the Phytolaccaceae family.

High-performance liquid chromatography analysis of plant saponins: An update 2005-2010

Saponins are widely distributed in plant kingdom. In view of their wide range of biological activities and occurrence as complex mixtures, saponins have been purified and separated by high-performance liquid chromatography using reverse-phase columns at lower wavelength. Mostly, saponins are not detected by ultraviolet detector due to lack of chromophores. Electrospray ionization mass spectrometry, diode array detector , evaporative light scattering detection, and charged aerosols have been used for overcoming the detection problem of saponins.

Rapid characterization of triterpene saponins from Conyza blinii by liquid chromatography coupled with mass spectrometry

Conyza blinii Le'vl is a medicinal herb used for the treatment of inflammation in Chinese folk medicine. Its major bioactive constituents are triterpene saponins, most of which contain 6-8 sugar residues. In this report, electrospray ionization tandem mass spectrometry fragmentation behaviors of bisdesmosidic triterpene saponins (conyzasaponin A, B, and C) were studied in both positive and negative ion modes with an ion-trap mass spectrometer. In full scan mass spectrometry, these saponins gave predominant [M-H](-) and [M+Na](+) ions, which determined the molecular weights. In tandem mass spectrometry (MS(n), n = 2-4), the [M-H](-) and [M+Na](+) ions yielded fragments [Y(0α)-H](-) and [B(α)+Na](+), which were diagnostic for the structures of the triterpene skeleton and sugar chains. The structural elucidation was approved by accurate mass data using IT-TOF-MS. An interpretation guideline based on MS(n) (n = 2-4) diagnostic ions was proposed in order to elucidate the chemical structures of unknown triterpene saponins in C. blinii extract. The saponins in C. blinii were separated by liquid chromatography with a methanol/acetonitrile/water solvent system, and then analyzed by ion-trap and IT-TOF mass spectrometers. Based on the interpretation guideline, a total of 35 triterpenoid saponins were tentatively identified. Among them, 15 saponins had been previously reported, and the other 20 saponins were reported from Conyza species for the first time. This study indicates that LC/MS is a powerful technology for the rapid characterization of complicated saponins in herbal extracts.

Rapid differentiation of isobaric and positional isomers of structurally related glycosides from Phytolacca bogotensis

Through the action of glycosyltransferases, a plant can biosynthetically assemble small different aglycons or 'templates' to various polysaccharides to produce numerous glycoconjugates differing in the type of the attached aglycon, the anomeric configuration of C-1 of the glycosylating sugar, the type of sugar and the different position of attachments of the sugar unit present in the polysaccharide chain. The position of attachments and the anomeric configuration of the different sugar present in the polysaccharide create the opportunity to generate molecules with either the same or very close molecular weights, which have relative structural similarity--forming isobaric and positional isomers. Although isomeric differentiation was once considered outside of the domain of mass spectrometry, this task can now be resolved using tandem mass spectrometry. In a standardized purified glycoconjugate fraction (SPT01) from Phytolacca bogotensis, we report conventional electrospray ionization mass spectrometry and collision-induced dissociation (CID) MS/MS parameters which favored the formation of characteristic product ions. This allowed us to suggest the type of sugar linkages present in a specific glycoconjugate. Ten new glycoconjugate are described from this plant and another twelve known saponins were structurally characterized using the automatic MSn acquisition mode. The differentiation of two pairs of positional isomers and four isobaric glycosides and the production of a library of 30 glycosides present in P. bogotensis were accomplished.