Secoiridoid Glycosides fromSwertia mileensis

Automated Composition Assessment of Natural Extracts: Untargeted Mass Spectrometry-Based Metabolite Profiling Integrating Semiquantitative Detection

Recent developments in mass spectrometry-based metabolite profiling allow unprecedented qualitative coverage of complex biological extract composition. However, the electrospray ionization used in metabolite profiling generates multiple artifactual signals for a single analyte. This leads to thousands of signals per analysis without satisfactory means of filtering those corresponding to abundant constituents. Generic approaches are therefore needed for the qualitative and quantitative annotation of a broad range of relevant constituents. For this, we used an analytical platform combining liquid chromatography-mass spectrometry (LC-MS) with Charged Aerosol Detection (CAD). We established a generic metabolite profiling for the concomitant recording of qualitative MS data and semiquantitative CAD profiles. The MS features (recorded in high-resolution tandem MS) are grouped and annotated using state-of-the-art tools. To efficiently attribute features to their corresponding extracted and integrated CAD peaks, a custom signal pretreatment and peak-shape comparison workflow is built. This strategy allows us to automatically contextualize features at both major and minor metabolome levels, together with a detailed reporting of their annotation including relevant orthogonal information (taxonomy, retention time). Signals not attributed to CAD peaks are considered minor metabolites. Results are illustrated on an ethanolic extract of Swertia chirayita (Roxb.) H. Karst., a bitter plant of industrial interest, exhibiting the typical complexity of plant extracts as a proof of concept. This generic qualitative and quantitative approach paves the way to automatically assess the composition of single natural extracts of interest or broader collections, thus facilitating new ingredient registrations or natural-extracts-based drug discovery campaigns.

Xanthones: Biosynthesis and Trafficking in Plants, Fungi and Lichens

Xanthones are a class of secondary metabolites produced by plant organisms. They are characterized by a wide structural variety and numerous biological activities that make them valuable metabolites for use in the pharmaceutical field. This review shows the current knowledge of the xanthone biosynthetic pathway with a focus on the precursors and the enzymes involved, as well as on the cellular and organ localization of xanthones in plants. Xanthone biosynthesis in plants involves the shikimate and the acetate pathways which originate in plastids and endoplasmic reticulum, respectively. The pathway continues following three alternative routes, two phenylalanine-dependent and one phenylalanine-independent. All three routes lead to the biosynthesis of 2,3',4,6-tetrahydroxybenzophenone, which is the central intermediate. Unlike plants, the xanthone core in fungi and lichens is wholly derived from polyketide. Although organs and tissues synthesizing and accumulating xanthones are known in plants, no information is yet available on their subcellular and cellular localization in fungi and lichens. This review highlights the studies published to date on xanthone biosynthesis and trafficking in plant organisms, from which it emerges that the mechanisms underlying their synthesis need to be further investigated in order to exploit them for application purposes.

Three new constituents from the Tujia ethnomedicine Swertia punicea Hemsl

Three new constituents: 1,5R-dihydroxy-3,8S-dimethoxy-5,6,7,8-tetrahydroxanthone (1), (3S,4R,16S,17R)-3,16,23-trihydroxyoleana-11,13(18)-dien-28-aldehyde-3-O-β-D-glucopyranoside (2), and new natural product (S)-gentiandiol (3), along with 41 known compounds were isolated from Tujia ethnomedicine Shuihuanglian, namely, the whole plant of Swertia punicea. Structures of all these compounds were established through extensive spectroscopic techniques, namely 1D, 2D-NMR spectroscopy, HRESIMS analysis, and the absolute configuration of the new compounds was discerned by circular dichroism (CD) spectroscopy. Antioxidative effects of these compounds were evaluated by using the DPPH radical scavenging method, compounds 7, 9 and 14 showed antioxidant activities with IC₅₀ values of 68.9, 50.8 and 48.2 μM, respectively.

The Effect of Terpenoids of Dipsacus Asperoides Against Alzheimer's Disease and Development of Simultaneous Analysis by High Performance Liquid Chromatography

Dipsaci Radix has been proved to represent an effective treatment strategy for Alzheimer's disease (AD), but the potential active components in Dipsaci Radix have not been evaluated by an AD-related bioassay. In this study, water fraction of Dipsaci Radix had been shown to have highest inhibitory effect on the AD-related activity tests, including inhibition of acetylcholinesterase (AChE), butyrylcholinesterase (BChE), β-site amyloid precursor protein cleaving enzyme 1 (BACE1), and advanced glycation end-product (AGE) formation. Therefore, a bioassay-guided approach yielded eleven terpenoid compounds (DR1-11) isolated from water fraction of Dipsaci Radix. Compounds (DR2,3,7 and 11) were stronger inhibitors of AChE. The BChE inhibitory effect of saponins was more positive than that of iridoids (DR1,4). Compounds (DR6,7,9-11) were good inhibitors of BACE1. Compounds (DR7-11) were more effective than positive control on the inhibition of AGE formation. Moreover, we firstly suggested concomitant new connections between the structure of Dipsaci Radix's isolated terpenoid compounds with AChE inhibitory activities and AGE formation. The study also represented that Dipsaci Radix was therapeutic for treating AD and dipsacus saponin XI (DR11) might be one of its active components. Our findings significantly provided the new foundation of the potential capacity bioactive components from Dipsaci Radix for AD remedy.

A new and effective evaluation method for Radix Gentianae Macrophyllae herbs based on 2-phenylethyl β-d-glucopyranoside, 2-methoxyanofinic acid and gentioxepine by UPLC-QTOF-MS exploring and HPLC-DAD quantification

Radix Gentianae Macrophyllae (RGM) is a traditional Chinese medicine belonging to the Gentiana genus and including four species of herbs. Owing to the lack of characteristic constituents, it is difficult to discriminate RGMs of different origins or even differentiate between herbs in the same genus. The current research aimed to explore the characteristic aromatic compounds, verify their significance in distinguishing different origins of RGM herbs and provide a simple and effective quality evaluation method. A selective extraction method was developed for noniridoid compounds and the extract was then subjected to UPLC-QTOF-MS analysis to obtain the RGM-MS ion pair database for noniridoid components. An HPLC-DAD quantitative analysis method was further developed based on characteristic aromatic compounds (2-phenylethyl β-d-glucopyranoside, 2-methoxyanofinic acid and gentioxepine) after the ion screening in the MS database. By means of principal component analysis and hierarchical clustering analysis analysis, the significant relationship between aromatic compounds contents and different species of RGM was revealed. As a result, the significance of 2-phenylethyl β-d-glucopyranoside, 2-methoxyanofinic acid and gentioxepine in distinguishing four species of RGM herbs was verified and a sensitive and reproducible HPLC-DAD method was established using these markers, which can be used for the classification and quantitative analysis of RGMs.

Rigenolides D-H, norsecoiridoid and secoiridoids from Gentiana rigescens Franch

Five new compounds, rigenolides D-H (1-5), were isolated from the aerial parts of Gentiana rigescens Franch. Their structures were assigned by detailed spectroscopic analyses and chemical conversions. Rigenolides D (1) and E (2) were elucidated to be a secoiridoid and a norsecoiridoid, respectively, possessing a dienone moiety in common. Rigenolides F-H (3-5) were assigned as acylated secoiridoid glucosides.

Targeted isolation and identification of bioactive compounds lowering cholesterol in the crude extracts of crabapples using UPLC-DAD-MS-SPE/NMR based on pharmacology-guided PLS-DA

The anti-hyperlipidemic effects of crude crabapple extracts derived from Malus 'Red jade', Malus hupehensis (Pamp.) Rehd. and Malus prunifolia (Willd.) Borkh. were evaluated on high-fat diet induced obese (HF DIO) mice. The results revealed that some of these extracts could lower serum cholesterol levels in HF DIO mice. The same extracts were also parallelly analyzed by LC-MS in both positive and negative ionization modes. Based on the pharmacological results, 22 LC-MS variables were identified to be correlated with the anti-hyperlipidemic effects using partial least square discriminant analysis (PLS-DA) and independent samples t-test. Further, under the guidance of the bioactivity-correlated LC-MS signals, 10 compounds were targetedly isolated and enriched using UPLC-DAD-MS-SPE and identified/elucidated by NMR together with MS/MS as citric acid(1), p-coumaric acid(2), hyperoside(3), myricetin(4), naringenin(5), quercetin(6), kaempferol(7), gentiopicroside(8), ursolic acid(9) and 8-epiloganic acid(10). Among these 10 compounds, 6 compounds, hyperoside(3), myricetin(4), naringenin(5), quercetin(6), kaempferol(7) and ursolic acid(9), were individually studied and reported to indeed have effects on lowering the serum lipid levels. These results demonstrated the efficiency of this strategy for drug discovery. In contrast to traditional routes to discover bioactive compounds in the plant extracts, targeted isolation and identification of bioactive compounds in the crude plant extracts using UPLC-DAD-MS-SPE/NMR based on pharmacology-guided PLS-DA of LC-MS data brings forward a new efficient dereplicated approach to natural products research for drug discovery.

Off-line coupling of new generation centrifugal partition chromatography device with preparative high pressure liquid chromatography-mass spectrometry triggering fraction collection applied to the recovery of secoiridoid glycosides from Centaurium erythraea Rafn. (Gentianaceae)

A purification sequence including a Gilson CPC 250 PRO device coupled to PrepHPLC hyphenated with a MS triggering fraction collector was applied to isolate secoiridoid glycosides from a complex methanolic extract of Centaurium erythraea. This species is widely used for ethnomedicinal purposes around the Mediterranean Sea. The solvent system ethyle acetate/ethanol/water 7.5/3/5 was determined using shake-flask method targeting swertiamarin, the major secoiridoid of the extract. Optimization of CPC experimental parameters enabled the injection of 4g of extract with a flow rate of 40mL/min at 3000rpm to provide a secoiridoid glycosides enriched fraction. 130mg of this latter was submitted to a second step of purification by preparative HPLC (gradient water/formic acid (19:1) (A) and methanol (B) as follows: 0min, 85% A; 8min, 60% A; 12min, 55% A; 35min, 55% A; 40min, 10% A; 50min, 10% A; 52min, 85% A; 55min, 85% A) to give swertiamarin (36mg, yield 27.7%, purity 98.2%). Other secoiridoid glycosides (sweroside, gentiopicroside, secologanol, secoxyloganin) were also isolated in minor amounts. As these monoterpene derivatives are responsible for several biological activities, their quick recovery with high yield and purity may serve as a model for further scale-up and industrial development.

Chemical Composition, Antioxidant and Anticholinesterase Activities of Gentianella azurea from Russian Federation

Phytochemical study of Gentianella azurea (Bunge) Holub (Gentianaceae) collected in Buryatia Republic (Russian Federation) resulted in the isolation of twenty-one compounds including bellidifolin, bellidin, isobellidifolin, norswertianolin, isobellidifolin-8- O-β-D-glucopyranoside, orientin, cynaroside, cosmosiin, apigenin, 4′- O-caffeoylswertiamarin, swertiamarin-6′- O-β-D-glucopyranoside and sweroside, firstly detected in this species. The extracts and individual compounds were shown to possess antioxidant and anticholinesterase potential.

A New Flavonol Triglycoside from Eustoma grandiflorum

A new flavonol triglycoside, kaempferol 3- O-α-L-rhamnopyranosyl (1→6)-(3- O- E- p-coumaroyl)-β-D-galactopyranoside-7- O-α-L-rhamnopyranoside (1: Eustograndifloside A) was isolated from the flower of Eustoma grandiflorum in addition to eight known flavonols (2: kaempferol 3- O-α-L-rhamnopyranosyl (1→6)-(4- O- E- p-coumaroyl)-β-D-galactopyranoside-7- O-α-L-rhamnopyranoside, 3: kaempferol 3- O-β-robinobioside-7- O-α-L-rhamnopyranoside, 4: isorhamne-tin 3- O-α-L-rhamnopyranosyl (1→2) [α-L-rhamnopyranosyl (1→6)]-(4- O- E- p-coumaroyl)-β-D-galactopyranoside-7- O-α-L-rhamnopyranoside, 5: kaempferol 3- O-α-L-rhamnopyranosyl (1→2) [α-L-rhamnopyranosyl (1→6)]-(4- O- E- p-coumaroyl)-β-D-galactopyranoside-7- O-α-L-rhamnopyranoside, 6: kaempferol 3- O-β-robinobioside, 7: quercetin 3- O-β-robinobioside, 8: isorhamnetin 3- O-β-robinobioside, and 9: kaempferol 7- O-α-L-rhamnopyranoside) and two known secoiridoid glycosides (10: swertiamarin and 11: sweroside). The structure elucidation of these compounds was accomplished through analyses of spectroscopic, including 1D and 2D NMR, and ESIMS data.

Rapid preparative separation of six bioactive compounds from Gentiana crassicaulis Duthie ex Burk. using microwave-assisted extraction coupled with high-speed counter-current chromatography

A rapid method combining microwave-assisted extraction (MAE) and high-speed counter-current chromatography (HSCCC) was applied for preparative separation of six bioactive compounds including loganic acid (I), isoorientin-4'-O-glucoside (II), 6'-O-β-d-glucopyranosyl gentiopicroside (III), swertiamarin (IV), gentiopicroside (V), sweroside (VI) from traditional Tibetan medicine Gentiana crassicaulis Duthie ex Burk. MAE parameters were predicted by central composite design response surface methodology. That is, 5.0 g dried roots of G. crassicaulis were extracted with 50 mL 57.5% aqueous ethanol under 630 W for 3.39 min. The extract (gentian total glycosides) was separated by HSCCC with n-butanol/ethyl acetate/methanol/1% acetic acid water (7.5:0.5:0.5:3.5, v/v/v/v) using upper phase mobile in tail-to-head elution mode. 16.3, 8.8, 12., 25.1, 40.7, and 21.8 mg of compounds I-VI were obtained with high purities in one run from 500 mg of original sample. The purities and identities of separated components were confirmed using HPLC with photo diode array detection and quadrupole TOF-MS and NMR spectroscopy. The study reveals that response surface methodology is convenient and highly predictive for optimizing extraction process, MAE coupled with HSCCC could be an expeditious method for extraction and separation of phytochemicals from ethnomedicine.

Minor secoiridoid aglycones from the low-polarity part of the traditional Chinese herb: Swertia mileensis

Eleven new secoiridoid aglycones involving unusual C₉-skeleton: swerimilegenins A-F (1–6); bis-C9-skeleton: swerimilegenin G (7); and C₁₀-skeleton: swerimilegenins H-K (8–11), as well as six known ones, were isolated from the low-polarity part of the traditional Chinese herb medicine Swertia mileensis. Their structures were determined by extensive spectroscopic data and X-ray diffraction. Biogenetically, swerimilegenin A (1) belonged to 10-nor-secoiridoid, and swerimilegenins B-F (2–6) were 1-nor-secoiridoids. Erythrocentaurin (12) and gentiogenal (15) showed moderate anti-HBV activity on HepG 2.2.15 cell line in vitro.

Rigenolide A, a new secoiridoid glucoside with a cyclobutane skeleton, and three new acylated secoiridoid glucosides from Gentiana rigescens Franch

Rigenolide A (1), a new secoiridoid glucoside with a cyclobutane skeleton and three new acylated secoiridoid glucosides, 2'-(2,3-dihydroxybenzoyl)-gentiopicroside (2), 2'-(2,3-dihydroxybenzoyl)-swertiamarin (3), 3'-(2,3-dihydroxybenzoyl)-sweroside (4), along with two noriridoids (7 and 8) and two known secoiridoid glucosides (5 and 6), were isolated from Gentiana rigescens Franch. The structures of new compounds were elucidated by extensive spectroscopic analyses. The isolated compounds were evaluated for DPPH free-radical scavenging activity.

Anti-hepatitis B virus active lactones from the traditional Chinese herb: Swertia mileensis

Swerilactones H-K (1-4), which are four novel lactones with an unprecedented C29 skeleton, were isolated from Swertia mileensis (Qing-Ye-Dan), an endemic Chinese herb used for treating viral hepatitis. Their structures were determined by extensive spectroscopic and X-ray crystallographic diffraction analyses. Swerilactones H-K exhibit potent anti-hepatitis B virus activity against HBV DNA replication with IC(50) values ranging from 1.53 to 5.34 μM. For the first time, a plausible biogenetic pathway for swerilactones H-K, together with the previously reported swerilactones A-D is proposed. From a biogenetic point of view, swerilactones A-D are ascribed as secoiridoid dimers, and swerilactones H-K as secoiridoid trimers.

Phytochemical Study of Fagraea spp. Uncovers a New Terpene Alkaloid with Anti-Inflammatory Properties

Phytochemical investigation of the stem bark of F. racemosa JACK ex WALL (Loganiaceae) from East Java, Indonesia, has resulted in the isolation of a new alkaloid fagraeoside along with the iridoid glycoside secologanoside. Fagraeoside may be derived from the condensation of secologanin with L-asparagine, and represents a rare example of a terpene alkaloid in which the amino acid component is non-aromatic. Investigation of three additional species of Fagraea provided known lignans, iridoid or secoiridoid glycosides, and flavanol-6-C-glucosides, thus it is likely that iridoid and secoiridoid glucosides are chemotaxonomic markers for the Fagraea genus. Fagraeoside inhibited the production of prostaglandin E2 in 3T3 murine fibroblasts (IC50 ~5.1 µM), and was not cytotoxic to this cell line or to a P388 murine leukaemia cell line. Selected isolated compounds, including fagraeoside, showed low to moderate activity in anti-acetylcholinesterase screening.

Swerilactones C and D, anti-HBV new lactones from a traditional Chinese herb: Swertia mileensis

Swerilactones C (1) and D (2), two novel diastereomeric lactones with an unprecedented 6/6/6/6/6 pentacyclic ring system, were isolated from the traditional Chinese herb Swertia mileensis. Their structures and relative stereochemistry were elucidated on the basis of spectroscopic methods and further confirmed by X-ray single-crystal diffraction analysis. In vitro antihepatitis B virus (HBV) assay on the Hep G 2.2.15 cell line showed that both compounds 1 and 2 exhibited inhibitory activities against the secretion of HBsAg (IC(50) = 1.24 and 2.96 mM, respectively) and HBeAg (IC(50) = 0.77 and 1.47 mM, respectively).

Liquid chromatography/tandem mass spectrometric study and analysis of xanthone and secoiridoid glycoside composition of Swertia chirata, a potent antidiabetic

Swertia chirata is a bitter plant, used in the Indian system of medicine (Ayurveda) for various human ailments. The bioactive constituents include the xanthone and secoiridoid glycosides consisting of mangiferin, amarogentin, amaroswerin, sweroside and swertiamarin. Methanolic extracts of S. chirata possess constituents with antidiabetic activities, which was investigated by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). Preliminary HPLC analyses were performed on a reversed-phase C18 column using gradient elution. In the LC/ESI-MS spectra, predominant [M+H]+ and [M+Na]+ ions were observed in positive ion mode and provided molecular mass information. The five components of S. chirata were structurally correlated and confirmed based on the fragmentation characteristics and information available in the literature. The fragmentation behavior of [M+H]+/[M+Na]+ ions of these components were deduced from the collision-induced dissociation (CID) spectra obtained from the selective on-column information-dependant acquisition (IDA) approach. Xanthone-C-glycoside showed characteristic fragment ions due to fragmentation in the C-glycosidic unit while iridoid-O-glycosides showed characteristic fragment ions due to cleavage in the glycoside linkage and retro-Diels-Alder (RDA) cleavage within an iridoid aglycone. Furthermore, on the basis of this information, an analytical assay was developed and validated to determine relative concentrations of mangiferin, amarogentin, amaroswerin, sweroside and swertiamarin. The detection was carried out using multiple reaction monitoring (MRM) in positive ionization mode with a total analysis time of 3.5 min. The method was successfully applied to standardize four different batches of herbal preparation on the basis of relative concentration of five bioactive components.