Tandem mass spectrometric characterization of acetylated polyhydroxy hellebosaponins, the principal steroid saponins in Helleborus niger L. roots(#)

Advances in the Biosynthesis and Molecular Evolution of Steroidal Saponins in Plants

Steroidal saponins are an important type of plant-specific metabolite that are essential for plants' responses to biotic and abiotic stresses. Because of their extensive pharmacological activities, steroidal saponins are also important industrial raw materials for the production of steroidal drugs. In recent years, more and more studies have explored the biosynthesis of steroidal saponins in plants, but most of them only focused on the biosynthesis of their molecular skeleton, diosgenin, and their subsequent glycosylation modification mechanism needs to be further studied. In addition, the biosynthetic regulation mechanism of steroidal saponins, their distribution pattern, and their molecular evolution in plants remain unclear. In this review, we summarized and discussed recent studies on the biosynthesis, molecular regulation, and function of steroidal saponins. Finally, we also reviewed the distribution and molecular evolution of steroidal saponins in plants. The elucidation of the biosynthesis, regulation, and molecular evolutionary mechanisms of steroidal saponins is crucial to provide new insights and references for studying their distribution, diversity, and evolutionary history in plants. Furthermore, a deeper understanding of steroidal saponin biosynthesis will contribute to their industrial production and pharmacological applications.

Medicinal Plant Analysis: A Historical and Regional Discussion of Emergent Complex Techniques

The analysis of medicinal plants has had a long history, and especially with regard to assessing a plant's quality. The first techniques were organoleptic using the physical senses of taste, smell, and appearance. Then gradually these led on to more advanced instrumental techniques. Though different countries have their own traditional medicines China currently leads the way in terms of the number of publications focused on medicinal plant analysis and number of inclusions in their Pharmacopoeia. The monographs contained within these publications give directions on the type of analysis that should be performed, and for manufacturers, this typically means that they need access to more and more advanced instrumentation. We have seen developments in many areas of analytical analysis and particularly the development of chromatographic and spectroscopic methods and the hyphenation of these techniques. The ability to process data using multivariate analysis software has opened the door to metabolomics giving us greater capacity to understand the many variations of chemical compounds occurring within medicinal plants, allowing us to have greater certainty of not only the quality of the plants and medicines but also of their suitability for clinical research. Refinements in technology have resulted in the ability to analyze and categorize plants effectively and be able to detect contaminants and adulterants occurring at very low levels. However, advances in technology cannot provide us with all the answers we need in order to deliver high-quality herbal medicines and the more traditional techniques of assessing quality remain as important today.

Preclinical evaluation of safety and potential of black hellebore extracts for cancer treatment

BACKGROUND

The therapeutic use of Helleborus niger L. is manifold due to its specific phytochemical composition. Two compound groups, the ranunculin derivates including protoanemonin and the steroidal saponins, are also associated with toxicity (genotoxicity, disintegration of membrane structures). Therefore, in vitro investigations were performed on safety aspects of a Helleborus niger aqueous fermented extract (HNE). In addition its therapeutic potential against various cancer cell lines was assessed to gain insight into the respective mechanisms of action.

METHODS

To evaluate the safe use of HNE, Ames and hemolytic tests were carried out. Two angiogenesis assays in 2D and 3D design were conducted to assess the anti-angiogenetic potential, for which human umbilical vein endothelial cells (HUVEC) were chosen. A panel of tumor cell lines was used in 2D and 3D proliferation assays as well in the migration- and invasion-assay. All investigations were performed with HNE compared to reference substances. The 2D proliferation assay was additionally performed with isolated compounds of HNE (characteristic steroidal saponins).

RESULTS

HNE did not exhibit any genotoxic potential. Concentrations up to 10 μl/ml were classified as non-hemolytic. HNE exerted anti-angiogenetic effects in HUVEC and anti-proliferative effects in five cancer cell lines, whereas hellebosaponin A and D as well macranthosid I did not show comparable effects neither singly nor in combination. Due to the inherent instability of protoanemonin in isolated form, parallel investigations with protoanemonin could not be performed. HNE (600-1000 μg/ml) inhibited the migration of certain cancer cells by > 80% such as Caki-2, DLD-1 and SK-N-SH.

CONCLUSION

HNE exhibit neither genotoxic nor hemolytic potential. The present investigations verify the anti-angiogenetic effects on HUVEC, the anti-proliferative effects and migration-inhibiting properties on tumor cells. The lower effect of the relevant steroidal saponins compared to the whole extract underlines the fact that the latter is more effective than a blend of isolated pharmacologically active components.

Recent advances in steroidal saponins biosynthesis and in vitro production

Steroidal saponins exhibited numerous pharmacological activities due to the modification of their backbone by different cytochrome P450s (P450) and UDP glycosyltransferases (UGTs). Plant-derived steroidal saponins are not sufficient for utilizing them for commercial purpose so in vitro production of saponin by tissue culture, root culture, embryo culture, etc, is necessary for its large-scale production. Saponin glycosides are the important class of plant secondary metabolites, which consists of either steroidal or terpenoidal backbone. Due to the existence of a wide range of medicinal properties, saponin glycosides are pharmacologically very important. This review is focused on important medicinal properties of steroidal saponin, its occurrence, and biosynthesis. In addition to this, some recently identified plants containing steroidal saponins in different parts were summarized. The high throughput transcriptome sequencing approach elaborates our understanding related to the secondary metabolic pathway and its regulation even in the absence of adequate genomic information of non-model plants. The aim of this review is to encapsulate the information related to applications of steroidal saponin and its biosynthetic enzymes specially P450s and UGTs that are involved at later stage modifications of saponin backbone. Lastly, we discussed the in vitro production of steroidal saponin as the plant-based production of saponin is time-consuming and yield a limited amount of saponins. A large amount of plant material has been used to increase the production of steroidal saponin by employing in vitro culture technique, which has received a lot of attention in past two decades and provides a way to conserve medicinal plants as well as to escape them for being endangered.

Pharmacology and psychiatry at the origins of Greek medicine: The myth of Melampus and the madness of the Proetides

Melampus is a seer-healer of Greek myth attributed with having healed the young princesses of Argos of madness. Analysis of this legend and its sources sheds light on the early stages of the "medicalizing" shift in the history of ancient Greek medicine. Retrospective psychological diagnosis suggests that the descriptions of the youths' madness rose from actual observation of behavioral and mental disorders. Melampus is credited with having healed them by administering hellebore. Pharmacological analysis of botanical specimens proves that Helleborus niger features actual neurological properties effective in the treatment of mental disorders. The discussion aims at examining the rational aspects of the treatment of mental conditions in Greco-Roman antiquity.

LC-MS(n) characterization of steroidal saponins in Helleborus niger L. roots and their conversion products during fermentation

Steroidal saponins comprise a substantial part of the secondary metabolite spectrum in the medicinal plant Helleborus niger L. (black hellebore). The saponin fraction from the roots was investigated by LC-MS(n) resulting in 38 saponins and β-ecdysone. Nine diosgenyl-type glycosides, mainly furostanols consisting of the aglycones diosgenin, macranthogenin, sceptrumgenin, and sarsasapogenin were accompanied by 5 diosgenyl-type saponins exhibiting an aglycone with an additional OH group. However, the most relevant compounds were 24 acetylated polyhydroxy saponins including hellebosaponins A and D. The enzymes glucuronidase, β-glucosidase, and pectinase were used to obtain an idea on potential fermentative transformation reactions by incubation of the isolated model saponins macranthosid I and hellebosaponin A. In a second step, aqueous H. niger extracts containing a much greater range of saponins were monitored during fermentation and 12months of storage. The metabolites were examined and assigned by LC-MS(n) and targeted extracted ion current (EIC) scan analyses. Good agreement was found among the results from the model compounds and the whole aqueous fermented extracts. The native diosgenyl-type furostanol saponins were converted to spirostanols under scission of hexoses. Alteration of the acetylated polyhydroxy saponins, exclusively spirostanols, took place following cleavage of acetyl groups and terminal deoxyhexoses. Most interestingly, the pentoses of the sugar chain at C(1) were not affected. Conversion of acetylated polyhydroxy saponins resulted in a final structure type which was stable and detectable, even after 12months of fermentation and storage.