Two new triterpenoid saponins from Platycodon grandiflorum

Comparative Transcriptomic Analysis on White and Blue Flowers of Platycodon grandiflorus to Elucidate Genes Involved in the Biosynthesis of Anthocyanins

BACKGROUND

Platycodon grandiflorus has long been used in Northeast Asia as a food and folk medicine to treat various diseases. The intense blue color of P. grandiflorus corolla is its characteristic feature.

OBJECTIVES

By comparing deep transcriptomic data of P. grandiflorus and its white cultivar, we intended to elucidate the molecular mechanisms concerning the biosynthesis of anthocyanins in this plant.

MATERIAL AND METHODS

We sampled blue mature flowers (PgB) and yellow young buds (PgY) of P. grandiflorus. Meanwhile, mature flowers (PgW) of P. grandiflorus white cultivar were also collected for RNA extraction and next-generation sequencing. After high-throughput sequencing, Trinity software was applied for de novo assembly and the resultant 49934 unigenes were subjected for expression analysis and annotation against NR, KEGG, UniProt, and Pfam databases.

RESULTS

In all, 32.77 Gb raw data were generated and the gene expression profile for the flowers of P. grandiflorus was constructed. Pathway enrichment analysis demonstrated that genes involved in flavone and flavonol biosynthesis were differently expressed.

CONCLUSIONS

The extremely low expression of flavonoid-3',5'-hydroxylase in PgY and PgW was regarded as the reason for the formation of its white cultivar. Our findings provided useful information for further studies into the biosynthetic mechanism of anthocyanins.

Components study on antitussive effect and holistic mechanism of Platycodonis Radix based on spectrum-effect relationship and metabonomics analysis

The antitussive effect of Platycodonis Radix is closely related to the components in saponins fraction of Platycodonis Radix extract (SFPRE); however, these active components and their holistic mechanism remain unknown. Hence, a new method by integrating spectrum-effect relationship analysis with metabolomics analysis was applied to study the active components and their holistic mechanism simultaneously. For spectrum-effect relationship analysis, chemical fingerprints of ten batches of SFPRE were developed using UHPLC-LTQ-Orbitrap MSn; antitussive effect were evaluated using a classic mice-cough model induced by ammonia liquor. Spectrum-effect relationship was analyzed by partial least squares regression (PLSR) analysis. For metabolomics analysis, the altered metabolites related to cough in serum were identified by UHPLC-Q-TOF/MS and orthogonal partial least squares-discriminant analysis (OPLS-DA); metabolic pathway analysis was depended on MetaboAnalyst 4.0, KEGG database, METLIN database and HMDB database. Our findings showed that 10 identified components of Polygalacin D (peak 26), Deapio-platycodin D (peak 21), Platycodin D (peak 23), β-Gentiotriosyl platycodigenin (peak 37), Platycoside G3 (peak 17), Platycoside C (peak 25), Platycodin D3 (peak 16), 3-O-β-D-glucopyranosyl platycodigenin (peak 33), Platycoside F (peak 19) and 3″-O-acetyl platycodin D3 (peak 15), and 2 unidentified components (peak 45 and 44) possessed antitussive effects. The metabolomics analysis result showed that 19 metabolites were potential biomarkers related to the cough, 16 of which could be restored to normal levels by SFPRE. These biomarkers were involved in arachidonic acid metabolism, linoleic acid metabolism and glycerophospholipid metabolism. The current study may facilitate the development of antitussive medicines with fewer side-effects based on Platycodonis Radix.

Mass Spectrometry-Based Metabolomic and Lipidomic Analyses of the Effects of Dietary Platycodon grandiflorum on Liver and Serum of Obese Mice under a High-Fat Diet

We aimed to identify metabolites involved in the anti-obesity effects of Platycodon grandiflorum (PG) in high-fat diet (HFD)-fed mice using mass spectrometry (MS)-based metabolomic techniques. C57BL/6J mice were divided into four groups: normal diet (ND)-fed mice, HFD-fed mice, HFD with 1% PG extract-fed mice (HPGL), and HFD with 5% PG extract-fed mice (HPGH). After 8 weeks, the HFD group gained more weight than the ND group, while dietary 5% PG extract attenuated this change. The partial least squares discriminant analysis (PLS-DA) score plots showed a clear distinction between experimental groups in serum and liver markers. We also identified 10 and 32 metabolites in the serum and liver, respectively, as potential biomarkers that could explain the effect of high-dose PG added to HFD-fed mice, which were strongly involved in amino acid metabolism (glycine, serine, threonine, methionine, glutamate, phenylalanine, ornithine, lysine, and tyrosine), TCA cycle (fumarate and succinate), lipid metabolism (linoleic and oleic acid methyl esters, oleamide, and cholesterol), purine/pyrimidine metabolism (uracil and hypoxanthine), carbohydrate metabolism (maltose), and glycerophospholipid metabolism (phosphatidylcholines, phosphatidylethanolamines, lysophosphatidylcholines, and lysophosphatidylethanolamines). We suggest that further studies on these metabolites could help us gain a better understanding of both HFD-induced obesity and the effects of PG.

Platycodon grandiflorus - an ethnopharmacological, phytochemical and pharmacological review

ETHNOPHARMACOLOGICAL RELEVANCE

Platycodon grandiflorus (Jacq.) A. DC., the sole species in genus Platycodon A. DC. (Campanulaceae) has a long history of use as a traditional herbal medicine for the treatments of cough, phlegm, sore throat, lung abscess, chest pain, dysuria, and dysentery. As a legal medicine and dietary supplement, it is also frequently used as an ingredient in health foods and vegetable dishes. The aim of this review is to provide up-to-date information on the botanical characterization and distribution, ethnopharmacology, phytochemistry, pharmacology, and toxicity of Platycodon grandiflorus based on literature published in recent years. It will build a foundation for further study of the mechanism of action and the development of better therapeutic agents and healthy products from Platycodon grandiflorus.

MATERIAL AND METHODS

All of the available information on Platycodon grandiflorus was collected via electronic search (using PubMed, SciFinder Scholar, CNKI, TPL (www.theplantlist.org), Google Scholar, Baidu Scholar, and Web of Science).

RESULTS

A comprehensive analysis of the literature obtained through the above-mentioned sources confirmed that ethno-medical uses of Platycodon grandiflorus have been recorded in China, Japan, Mongolia, and Korea for thousands of years. A phytochemical investigation revealed that this product contains steroidal saponins, flavonoids, polyacetylenes, sterols, phenolics, and other bioactive compounds. Crude extracts and pure compounds isolated from Platycodon grandiflorus exhibited significant anti-inflammatory and immunostimulatory effects. They also showed valuable bioactive effects, such as anti-tumor, anti-oxidant, anti-diabetic, anti-obesity, hepatoprotective and cardiovascular system effects, among others.

CONCLUSIONS

In light of its long traditional use and the modern phytochemical and pharmacological studies summarized here, Platycodon grandiflorus has been demonstrated to show a strong potential for therapeutic and health-maintaining uses. Both the extracts and chemical components isolated from the plant showed a wide range of biological activities. Thus, more studies on the pharmacological mechanisms of its main active compounds (e.g., platycodin D, D2) need to be conducted. In addition, as one of the most popular traditional herbal medicines, clinical studies of the main therapeutic aspects, toxicity and adverse effects of Platycodon grandiflorus will also undoubtedly be the focus of future investigation.

An HPLC-MS/MS method for the quantitative determination of platycodin D in rat plasma and its application to the pharmacokinetics of Platycodi Radix extract

AIMS

To develop an HPLC-MS/MS method for the quantification of platycodin D (PD) in rat plasma, and to acquire the main pharmacokinetic parameters of PD after oral administration of pure PD or of Platycodi Radix extract (PRE) containing PD.

METHOD

Plasma samples were pretreated with solid-phase extraction using an Oasis® HLB SPE cartridge. Madecassoside was used as the internal standard (IS). Chromatographic separation was achieved on an ODS column (100 mm × 2.1 mm i.d., 3.5 μm) with a mobile phase consisting of acetonitrile/water (30 : 70, V/V) containing 0.1 mmol·L(-1) ammonium acetate at a flow rate of 0.25 mL·min(-1). The detection was performed on a triple quadruple tandem mass spectrometer using an electrospray ionization (ESI) source with a chromatographic run time of 3.0 min. The detection was operated by multiple reaction monitoring (MRM) of the transitions of m/z 1 223.6→469.2 for PD and of m/z 973.6→469.2 for madecassoside (IS), respectively.

RESULTS

The calibration curve was linear from 5 to 2 000 ng·mL(-1) (r(2) >0.99) with a lower limit of quantification (LLOQ) of 5 ng·mL(-1). The intra- and inter-day precision (relative standard deviation, RSD) values were below 15% and the accuracy (relative error, RE) was from -15% to +15% at three quality control (QC) levels. Plasma concentrations of PD were determined for 24 h after i.v. administration of PD, and oral administration of PD and PRE, respectively. The absolute oral bioavailability of PD in rats was found to be (0.48 ± 0.19)% when administered PD, and to be (1.81 ± 0.89)% when administered PRE.

CONCLUSION

The developed HPLC-MS/MS method was successfully applied to assess the pharmacokinetic parameters and oral bioavailability of PD in rats after administration of PD and Platycodi Radix extract.

Crude saponins from Platycodon grandiflorum induce apoptotic cell death in RC-58T/h/SA#4 prostate cancer cells through the activation of caspase cascades and apoptosis-inducing factor

Saponins are a major active component of Platycodon grandiflorum (P. grandiflorum) and are known to induce apoptosis in metastatic prostate cancer cell lines. However, thus far, no research has been conducted on the anticancer activity of saponins in RC-58T/h/SA#4 primary prostate cancer cells. In this study, we show that the treatment of prostate cancer cells with saponins extracted from P. grandiflorum (SPG) inhibits cell proliferation in a dose-dependent manner. SPG significantly induced apoptotic cell death, resulting in an increase in the sub-G1 apoptotic cell population, apoptotic DNA fragmentation and morphological changes. Pre-treatment with a caspase inhibitor modestly attenuated the SPG-induced increase in the sub-G1 cell population, suggesting that caspases play a role in SPG-induced apoptosis. Moreover, SPG-induced apoptosis was associated with changes in caspase activity, the upregulation of the apoptotic protein, Bax and the downregulation of the anti-apoptotic protein, Bcl-2. Furthermore, the caspase-independent mitochondrial apoptosis factor, apoptosis-inducing factor (AIF) was upregulated following SPG treatment. These findings indicate that SPG exerts its anticancer effects on RC-58T/h/SA#4 primary prostate cancer cells through mitochondrial caspase-dependent and -independent apoptotic pathways.

Two new oleanane-type triterpenoids from Platycodi Radix and anti-proliferative activity in HSC-T6 cells

Two new oleanane-type triterpenoids, named platycodonoids A and B (1, 2), together with five known saponins, including platycodin D (3), deapioplatycodin D (4), 3-O-β-D-glucopyranosyl polygalacic acid (5), 3-O-β-D-glucopyranosyl platycodigenin (6) and polygalacin D (7), were isolated from the roots of Platycodon grandiflorum. On the basis of spectral data and chemical evidence, the structures of the new compounds were elucidated as 2β,3β,23,24-tetrahydroxy-28-nor-olean-12-en-16-one (1) and 2β,3β,23,24- tetrahydroxy-28-nor-olean-12-en-16-one-3-O-β-D-glucopyranoside (2). Compounds 1-7 were evaluated for their in vitro anti-proliferative activity against the HSC-T6 cell line.

Platycoside N: a new oleanane-type triterpenoid saponin from the roots of Platycodon grandiflorum

A new oleanane-type triterpenoid saponin, named platycoside N (1), together with six known saponins, was isolated from the roots of Platycodon grandiflorum. On the basis of acid hydrolysis, comprehensive spectroscopic data analyses and comparison with the spectral data of the known compounds, its structure was elucidated as 3-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl-2β,3β,16α,23-tetrahydroxyolean-12-en-28-oic acid 28-O-β-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside. The six known compounds were platycodin D (2), deapioplatycodin D (3), platycodin D₃ (4), deapio- platycodin D₃ (5), platycoside E (6) and deapioplatycoside E (7).

Antiproliferative effects of saponins from the roots of Platycodon grandiflorum on cultured human tumor cells

Three new triterpenoid saponins, platyconic acid B lactone (1), deapio-platyconic acid B lactone (2), and deapio-platycodin D(2) (3), together with 17 known triterpenoid saponins, were isolated from a root extract of Platycodon grandiflorum. The structures of 1-3 were determined on the basis of spectroscopic data interpretation and chemical transformation. Saponins with a platycodigenin or polygalacic acid unit as a sapogenin demonstrated significant inhibitory effects on the proliferation of a small panel of cultured human tumor cells.

An efficient protocol for genetic transformation of Platycodon grandiflorum with Agrobacterium rhizogenes

The balloon flower (Platycodon grandiflorum) is a popular traditional medicinal plant used in Korea to treat conditions such as bronchitis, asthma, tuberculosis, diabetes, and inflammatory diseases. Recently, immunopharmacological research identified triterpenoid and saponin as important active compounds in P. grandiflorum. To study and extract these compounds and other metabolites from P. grandiflorum, a technique was developed for producing hairy root cultures, which are a reliable source of plant compounds. To achieve this, the activity of Agrobacterium rhizogenes was exploited, which can transfer DNA segments into plant genomes after infecting them. In this study, the A. rhizogenes strain R1000 was determined that had the highest infection frequency (87.5%) and induced the most hairy roots per plant, and the concentration of antibiotics (75 mg/l kanamycin) was elucidated for selection after transformation. Wild-type and transgenic hairy roots contained various phenolic compounds, although both of them had similar concentrations of phenolic compounds. In the future, the protocols described here should be useful for studying and extracting valuable metabolites such as phenolic compounds from P. grandiflorum hairy root cultures.

Preparative isolation of six major saponins from Platycodi Radix by high-speed counter-current chromatography

INTRODUCTION

Platycosides, the primary constituents of Platycodi Radix, are known to have numerous and varied biological activities, exerting anti-inflammation, anti-allergy, anti-tumour, anti-obesity and anti-hyperlipidemia effects. However, effective methods for isolating and purifying platycosides from Platycodi Radix are not currently available.

OBJECTIVE

To develop an efficient method for the preparative separation of six platycosides from Platycodi Radix by high-speed counter-current chromatography (HSCCC) coupled with an evaporative light scattering detection (ELSD) system.

METHODOLOGY

Preparative separation was performed by water extraction using reversed-phase C(18) column chromatography on an HSCCC-ELSD system. A two-phase solvent system comprised hexane-n-butanol-water (1:40:20, v/v) and (1:10:5, v/v) was employed. Two other key parameters, revolution speed of the separation column and flow-rate of the mobile phase, were also investigated for optimum HSCCC performance. Each peak fraction obtained from separation of the platycosides was collected according to the ELSD elution profile and determined by HPLC.

RESULTS

Using the described method, six platycosides, all with purities of over 94%, could be isolated from 300 mg of the platycoside-enriched fraction. Their structures were characterized by electrospray ionisation mass spectrometry (ESI-MS), (1)H-NMR and (13)C-NMR.

CONCLUSION

Six of the main bioactive platycosides in Platycodi Radix could be isolated and purified systematically by HSCCC.

Platyconic acid A, a genuine triterpenoid saponin from the roots of Platycodon grandiflorum

A genuine triterpenoid saponin, platyconic acid A (1) was isolated from the roots extract of Platycodon grandiflorum, together with five known saponins: deapioplatycoside E (2), platycoside E (3), platycodin D₃ (4), platycodin D₂ (5) and platycodin D (6). The structure of 1 was determined on the basis of spectral analysis and chemical evidence.

Ameliorating effect of balloon flower saponin on the ethanol-induced memory impairment in mice

The ameliorating effect of the root extract of Platycodon grandiflorum (Campanulaceae) on ethanol-induced cognitive dysfunction in mice was investigated. The mice with repeated administration of the root extract of P. grandiflorum, crude saponin fraction and platycoside E, a main ingredient of crude saponin fraction, showed a markedly prolonged step-through latency period (STL) on the passive avoidance task performed after acute ethanol intoxication, respectively. The present results suggest that the memory enhancing effect of the extract was ascribed mainly to the saponin fraction and that saponin of P. grandiflorum, particularly platycoside E could exert a beneficial effect on memory impairment in mice.

Cytotoxic triterpenoid saponins from the roots of Platycodon grandiflorum

Bioguided fractionation of the ethanol extracts obtained from Platycodon grandiflorum roots led to isolation of two new triterpenoid saponins, characterized as 3-O-beta-D-glucopyranosyl-2beta,12alpha,16alpha,23,24-pentahydroxyoleanane-28(13)-lactone (1) and 3-O-beta-D-glucopyranosyl-(1-->3)-beta-D-glucopyranosyl-2beta,12alpha,16alpha,23alpha-tetrahydroxyoleanane-28(13)-lactone (2) by 1D- and 2D-NMR and MS techniques, as well as chemical means. Both compounds showed cytotoxic activity against human ECA-109 cells.

Triterpenoid saponins from Platycodon grandiflurum

A new bisdesmosidic saponin, named deapio-platycoside E (1), together with two known triterpenoid saponins (2, 3) were isolated from the roots of Platycodon grandiflorum (Jacq.) A. D.C. Their structures were elucidated by spectroscopic and chemical methods.

Biological activities and distribution of plant saponins

Plant saponins are widely distributed amongst plants and have a wide range of biological properties. The more recent investigations and findings into their biological activities were summarized. Isolation studies of saponins were examined to determine which are the more commonly studied plant families and in which families saponins have been identified.

Antioxidant and anticancer activities of organic extracts from Platycodon grandiflorum A. De Candolle roots

This study examined the antioxidant and anticancer activities of the petroleum ether extracts from the roots of Platycodon grandiflorum A. DC, which is a plant used as both a herbal medicine and food in Asia. Extracts from Platycodon grandiflorum in petroleum ether were fractionated (fractions I-V) by silica gel column chromatography using gradient solvents (petroleum ether: ethyl ether, 9:1-5:5, v/v). The antioxidant activities of the fractions were evaluated in terms of their inhibition of lipid peroxidation as well as their free radical scavenging activity. Fraction II, which was extracted at an 8:2 mixture of petroleum ether and ethyl ether, exhibited the greatest antioxidant activity among the fractions. On the other hand, the cytotoxicity of each fraction, which was evaluated by the MTT assay using human cancer cell lines (HT-29, HRT-18 and HepG2), was greatest in fraction III, which was extracted with a 7:3 petroleum ether and ethyl ether mixture. Both fractions, II and III, were sub-fractionated by thin layer chromatography, and the sub-fractions each were screened for their antioxidant and anticancer activities. In addition, the antioxidant activity was closely related to the content of phenolic compounds, and the anticancer active fraction exhibited a typical UV absorbance spectrum of polyacetylene.