Bioactive neolignan, iridoid and flavonoid glycosides from the leaves of Vaccinium bracteatum

Two neolignan glycosides including a new one (1), along with seven iridoid glycosides (3 - 9) and nine flavonoid glycosides (10 - 18), were isolated from the leaves of Vaccinium bracteatum. Their structures were established mainly on the basis of 1D/2D NMR and ESIMS analyses, as well as comparison to known compounds in the literature. The structure of 1 with absolute stereochemistry was also confirmed by chemical degradation and ECD calculation. Selective compounds showed antiradical activity against ABTS and/or DPPH. Moreover, several isolates also suppressed the production of ROS in RAW264.7 cells and exerted neuroprotective effect toward PC12 cells.

Four new iridoid glycosides from the roots of Rehmannia glutinosa

Four new iridoid glycosides (1-4), rehmaglutosides L-O, were isolated from the air-dried roots of Rehmannia glutinosa. Their structures were established from the spectroscopic data obtained and by chemical evidence. The known mellittoside (5) and ajugol (6) were also obtained in the current investigation, and the structure of mellittoside was unequivocally defined using X-ray diffraction data. Compounds 1-6 were tested for their cytotoxicity against five human tumor cell lines and proliferation effects on Lactobacillus Reuteri.

Distribution profile of iridoid glycosides and phenolic compounds in two Barleria species and their correlation with antioxidant and antibacterial activity

INTRODUCTION

Barleria prionitis is known for its medicinal properties from ancient times. Bioactive iridoid glycosides and phenolic compounds have been isolated from leaves of this plant. However, other parts of a medicinal plants are also important, especially roots. Therefore, it is important to screen all organs for complete chemical characterization.

METHOD

All parts of B. prionitis, including leaf, root, stem and inflorescence in search of bioactive compounds, with a rapid and effective metabolomic method. X500R QTOF system with information dependent acquisition (IDA) method was used to collect high resolution accurate mass data (HRMS) on both the parent (MS signal) and their fragment ions (MS/MS signal). ESI spectra was obtained in positive ion mode from all parts of the plant. A comparative analysis of antioxidant and antibacterial activity was done and their correlation study with the identified compounds was demonstrated. Principal component analysis was performed.

RESULT

Iridoid glycosides and phenolic compounds were identified from all parts of the showing variability in presence and abundance. Many of the compounds are reported first time in B. prionitis. Antioxidant and antibacterial activity was revealed in all organs, root being the most effective one. Some of the iridoid glycoside and phenolic compounds found to be positively correlated with the tested biological activity. Principal component analysis of the chemical profiles showed variability in distribution of the compounds.

CONCLUSION

All parts of B. prionitis are rich source of bioactive iridoid glycosides and phenolic compounds.

Hepatoprotective Principles from the Rhizomes of Picrorhiza kurroa

A methanol extract of rhizomes of Picrorhiza kurroa Royle ex Benth. (Plantaginaceae) showed hepatoprotective effects against D-galactosamine (D-GalN)/lipopolysaccharide (LPS)-induced liver injury in mice. We had previously isolated 46 compounds, including several types of iridoid glycosides, phenylethanoid glycosides, and aromatics, etc., from the extract. Among them, picroside II, androsin, and 4-hydroxy-3-methoxyacetophenone exhibited active hepatoprotective effects at doses of 50-100 mg/kg, per os (p.o.) To characterize the mechanisms of action of these isolates and to clarify the structural requirements of phenylethanoid glycosides for their hepatoprotective effects, their effects were assessed in in vitro studies on (i) D-GalN-induced cytotoxicity in mouse primary hepatocytes, (ii) LPS-induced nitric oxide (NO) production in mouse peritoneal macrophages, and (iii) tumor necrosis factor-α (TNF-α)-induced cytotoxicity in L929 cells. These isolates decreased the cytotoxicity caused by D-GalN without inhibiting LPS-induced macrophage activation and also reduced the sensitivity of hepatocytes to TNF-α. In addition, the structural requirements of phenylethanoids for the protective effects of D-GalN-induced cytotoxicity in mouse primary hepatocytes were evaluated.

Two new iridoid glycosides from Hedyotis diffusa

Two new iridoid glycosides, named productasperulosidic acid butyl ester (1) and E-6-O-3-hydroxy-p-methoxycinnamoyl scandoside methyl ester (2), along with nine known ones (3-11), were isolated from Hedyotis diffusa Willd. The structures of them were elucidated by extensive 1D, 2D NMR and HR-ESI-MS spectral data. Compounds 1-11 showed no significant cytotoxic activity against HeLa cells.

Effects of 5-azaC on Iridoid Glycoside Accumulation and DNA Methylation in Rehmannia glutinosa

Iridoid glycoside is the important secondary metabolite and the main active component in Rehmannia glutinosa. However, the mechanisms that underlie the regulation of iridoid glycoside biosynthesis remain poorly understood in R. glutinosa. Herein, the analysis of RNA-seq data revealed that 3,394 unigenes related to the biosynthesis of secondary metabolites were identified in R. glutinosa. A total of 357 unigenes were involved in iridoid glycoside synthesis, in which the highly conservative genes, such as DXS, DXR, GPPS, G10H, and 10HGO, in organisms were overexpressed. The analysis of the above genes confirmed that the co-occurrence ratio of DXS, DXR, and GPPS was high in plants. Further, our results showed that under normal and 5-azacytidine (5-azaC) treatment, the expression levels of DXS, DXR, GPPS, G10H, and 10HGO were consistent with the iridoid glycoside accumulation in R. glutinosa, in which the application of the different concentrations of 5-azaC, especially 50 μM 5-azaC, could significantly upregulate the expression of five genes above and iridoid glycoside content. In addition, the changes in the spatiotemporal specificity of degree and levels of DNA methylation were observed in R. glutinosa, in which the hemi-methylation was the main reason for the change in DNA methylation levels. Similar to the changes in 5-methyl cytosine (5mC) content, the DNA demethylation could be induced by 5-azaC and responded in a dose-dependent manner to 15, 50, and 100 μM 5-azaC. Taken together, the expression of iridoid glycoside synthesis gene was upregulated by the demethylation in R. glutinosa, followed by triggering the iridoid glycoside accumulation. These findings not only identify the key genes of iridoid glycoside synthesis from R. glutinosa, but also expand our current knowledge of the function of methylation in iridoid glycoside accumulation.

Iridoid Glycosides from Phlomis Medicinalis Diels: Optimized Extraction and Hemostasis Evaluation

Phlomis medicinalis Diels, an important perennial herbal plant unique to the Qinghai-Tibet Plateau, is often used as Tibetan Materia Medicine Radix Phlomii for the treatment of cold, cough, and convergence trauma. In order to efficiently extract the iridoid glycosides from P. medicinalis, an ultrasound-assisted deep eutectic solvent extraction technique was employed. The main parameters influencing the extraction process were studied through single-factor tests and the extraction was optimized by using response surface methodology. The hemostasis activity of total iridoid glycosides (TIG) from P. medicinalis was evaluated in vitro and in mice. The optimization results revealed that the optimal process parameters were liquid-solid ratio 20 : 1, choline chloride-lactic acid concentration 79 %, and sonication time 34 min, under which a TIG extraction yield of 20.73 % was obtained. Meanwhile, high-performance liquid chromatography-photodiode array/mass spectrometry (HPLC-PDA/MS) was employed to characterize the optimized extract and indicated that TIG from P. medicinalis mainly consisted of sixteen reported iridoid glycosides with a total content of 91.22 %. The experimental results in vivo and in vitro indicated that TIG from P. medicinalis had strong hemostasis activities, which may be achieved by increasing the fibrinogen levels. Therefore, the ultrasound-assisted deep eutectic solvent extraction is an effective method to extract iridoid glycosides from P. medicinalis and they will be promising candidates to be developed for medical hemostasis agents.

Four new terpenoids and other metabolites with potential anti-complementary activities from the aerial parts of Dracocephalum moldavica (Lamiaceae)

In the course of our continuing search for biologically active compounds from medicinal herbs, four undescribed terpenoids including one monoterpenoid glycoside, (1 R, 3S, 4S, 5 R)-(-)-1,8-epoxy-p-menthan-5-ethoxycarbonyl-3-O-β-D-glucopyranoside (1), one iridoid glycoside, 3'-O-β-D-glucopyranosyl-melampyroside (2), one sesquiterpene, 1-(2-methylbutanol)-2-pentyl-1,3-cyclohexadiene (3), and one triterpenoid, 28-nor-3β,18β-dihydroxyurs-12-ene (4), together with nine known terpenoids (5-13) were isolated from the dried aerial parts of Dracocephalum moldavica (Lamiaceae). Their chemical structures were elucidated by detailed spectroscopy (1 D and 2 D NMR), HRESIMS data analysis and acid hydrolysis. Among them, compounds 9 and 10 were isolated from the family Lamiaceae, compounds 5, 6 and 11-13 were identified from the genus Dracocephalum and compounds 7 and 8 were reported from the D. moldavica for the first time. The biological evaluation of anti-complementary activity revealed that some compounds, 4, 6 and 12 exhibited anti-complementary activity with CH₅₀ and AP₅₀ values ranging from 0.67-1.43 and 1.12-1.55 mM, respectively.

Pterocephanoside A, a new iridoid from a traditional Tibetan medicine, Pterocephalus hookeri

This work obtained and identified pterocephanoside A (1), one new iridoid glucoside derivative with rare structure of three iridoid glycosides linked to cyclopenta[c]pyran-3(1H)-one, and 10 known iridoids (2-11) from Pterocephalus hookeri through silica gel column chromatography and semi-preparative HPLC. The structure of the new compound was confirmed by 1D and 2D NMR and HRMS data analysis. Compounds 1 and 2 were isolated from this plant for the first time. The iridoids mostly possessed seco-iridoid subtype and iridoid subtype skeletons from P. hookeri. Compounds 1, 3, 4, and 6-11 showed weak anti-inflammatory activity.

A New Geniposidic Acid Derivative Exerts Antiaging Effects through Antioxidative Stress and Autophagy Induction

Two compounds that can prolong the replicative lifespan of yeast, geniposidic acid (Compound 1) and geniposide (Compound 2), were isolated from Gardenia jasminoides Ellis. Compared with Compound 1, Compound 2 was different at C11 and showed better bioactivity. On this basis, seven new geniposidic derivatives (3-9) were synthesized. Geniposidic 4-isoamyl ester (8, GENI), which remarkably prolonged the replicative and chronological lifespans of K6001 yeast at 1 µM, was used as the lead compound. Autophagy and antioxidative stress were examined to clarify the antiaging mechanism of GENI. GENI increased the enzymes activities and gene expression levels of superoxide dismutase (SOD) and reduced the contents of reactive oxygen species (ROS) and malondialdehyde (MDA) to improve the survival rate of yeast under oxidative stress. In addition, GENI did not extend the replicative lifespan of ∆sod1, ∆sod2, ∆uth1, ∆skn7, ∆cat, and ∆gpx mutants with K6001 background. The free green fluorescent protein (GFP) signal from the cleavage of GFP-Atg8 was increased by GENI. The protein level of free GFP showed a considerable increase and was time-dependent. Furthermore, GENI failed to extend the replicative lifespans of ∆atg32 and ∆atg2 yeast mutants. These results indicated that antioxidative stress and autophagy induction were involved in the antiaging effect of GENI.

Diagnostic ion filtering targeted screening and isolation of anti-inflammatory iridoid glycosides from Hedyotis diffusa

Efficient and targeted screening and isolation of bioactive compounds from complex natural products is still a challenging work. Herein, diagnostic ion filtering based high-performance liquid chromatography-quadrupole time-of-flight-tandem mass spectrometry was firstly developed to screen six main iridoid glycosides from Hedyotis diffusa. Then, online extraction-high-speed counter current chromatography was proposed for targeted enrichment and preparative isolation using ethyl acetate/n-butanol/water (4.5:0.5:5, v/v/v) as solvent system. After that, Sephadex LH-20 column chromatography using methanol as solvent system was selected for further purification of six iridoid glycosides with purities over 98%. They were finally identified as monotropein, desacetylasperuloside acid, asperuloside, 6-O-(Z)-p-coumaroyl scandoside methyl ester, 6-O-(Z)-feruloyl scandoside methyl ester, and 6-O-(E)-p-coumaroyl scandoside methyl ester. And their anti-inflammatory activities were evaluated and confirmed by lipopolysaccharide activated RAW 264.7 macrophages. Obviously, the results provide a scientific basis for the potential applications of H. diffusa, and the developed methodology is efficient and reliable for targeted screening and isolation of bioactive compounds from natural products.

Nine Unique Iridoids and Iridoid Glycosides From Patrinia scabiosaefolia

Patrinia scabiosaefolia is a medical and edible Chinese herb with high nutritional and medicinal value. The continuing study of its chemical constituents led to the discovery of nine unique iridoids and iridoid glycosides, including three new iridoids (1-3) and six previously unknown irioid glycosides (5-10), and one known compound (4). Among them, compound 1 was a deformed iridoid, while compounds 3, 5-7, and 10 formed a new ring in their skeletons which was uncommon in this genus. For compound 3, the new ring existed between C-3 and C-10, while a 1,3-dioxane appeared between C-7 and C-10 in compounds 5-7 and 10. Moreover, compound 10 was a bis-iridoid glycoside, which was the first reported in P. scabiosaefolia. And the sugar of irioid glycosides (5-10) was glucose at C-11, except in 9 which had a 5-deoxyglucose moiety. All their structures were confirmed based on the extensive spectroscopic analysis, including IR, UV, HR-ESI-MS, ECD, and 1D- and 2D-NMR experiments. Their cytotoxic activities against HL-60, A-549, SMMC-7721, MCF-7, SW480 were also tested.

Dual Functional Eudragit® S100/L30D-55 and PLGA Colon-Targeted Nanoparticles of Iridoid Glycoside for Improved Treatment of Induced Ulcerative Colitis

AIM

Iridoid glycosides (IG) as the major active fraction of Syringa oblata Lindl. has a proven anti-inflammatory effect for ulcerative colitis (UC). However, its current commercial formulations are hampered by low bioavailability and unable to reach inflamed colon. To overcome the limitation, dual functional IG-loaded nanoparticles (DFNPs) were prepared to increase the residence time of IG in colon. The protective mechanism of DFNPs on DSS-induced colonic injury was evaluated in rats.

MATERIALS AND METHODS

We prepared DFNPs using the oil-in-water emulsion method. PLGA was selected as sustained-release polymer, and ES100 and EL30D-55 as pH-responsive polymers. The morphology and size distribution of NPs were measured by SEM and DLS technique. To evaluate colon targeting of DFNPs, DiR, was encapsulated as a fluorescent probe into NPs. Fluorescent distribution of NPs were investigated. The therapeutic potential and in vivo transportation of NPs in gastrointestinal tract were evaluated in a colitis model.

RESULTS

SEM images and zeta data indicated the successful preparation of DFNPs. This formulation exhibited high loading capacity. Drug release results suggested DFNPs released less than 20% at the first 6 h in simulated gastric fluid (pH1.2) and simulated small intestine fluid (pH6.8). A high amount of 84.7% sustained release from NPs in simulated colonic fluid (pH7.4) was beyond 24 h. DiR-loaded NPs demonstrated a much higher colon accumulation, suggesting effective targeting due to functionalization with pH and time-dependent polymers. DFNPs could significantly ameliorate the colonic damage by reducing DAI, macroscopic score, histological damage and cell apoptosis. Our results also proved that the potent anti-inflammatory effect of DFNPs is contributed by decrease of NADPH, gene expression of COX-2 and MMP-9 and the production of TNF-α, IL-17, IL-23 and PGE2.

CONCLUSION

We confirm that DFNPs exert protective effects through inhibiting the inflammatory response, which could be developed as a potential colon-targeted system.

A new diterpernoid glycoside from the fruit of Forsythia suspensa

One new diterpernoid glycoside, lanceolatinoside A (1), together with one known iridoid glycoside, luzonoside C (2) were isolated from the fruit of Forsythia suspensa. The structure of the new compound (1) was elucidated through 1 D and 2 D NMR spectroscopic data, and HR-ESIMS. Compound 2 was identified as luzonoside C (2) on the basis of NMR spectroscopic data analyses and comparison with those reported in the literature.

Bioassay-Guided Isolation of Anti-Alzheimer Active Components from the Aerial Parts of Hedyotis diffusa and Simultaneous Analysis for Marker Compounds

Previous studies have reported that Hedyotis diffusa Willdenow extract shows various biological activities on cerebropathia, such as neuroprotection and short-term memory enhancement. However, there has been a lack of studies on the inhibitory activity on neurodegenerative diseases such as Alzheimer's disease (AD) through enzyme assays of H. diffusa. Therefore, H. diffusa extract and fractions were evaluated for their inhibitory effects through assays of enzymes related to AD, including acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), and β-site amyloid precursor protein cleaving enzyme 1 (BACE1), and on the formation of advanced glycation end-product (AGE). In this study, ten bioactive compounds, including nine iridoid glycosides 1-9 and one flavonol glycoside 10, were isolated from the ethyl acetate and n-butanol fractions of H. diffusa using a bioassay-guided approach. Compound 10 was the strongest inhibitor of cholinesterase, BACE1, and the formation of AGEs of all isolated compounds, while compound 5 had the lowest inhibitory activity. Compounds 3, 6, and 9 exhibited better inhibitory activity than other compounds on AChE, and two pairs of diastereomeric iridoid glycoside structures (compounds 4, 8, and 6, 7) showed higher inhibitory activity than others on BChE. In the BACE1 inhibitory assay, compounds 1-3 were good inhibitors, and compound 10 showed higher inhibitory activity than quercetin, the positive control. Moreover, compounds 1 and 3 were stronger inhibitors of the formation of AGE than aminoguanidine (AMG), the positive control. In conclusion, this study is significant since it demonstrated that the potential inhibitory activity of H. diffusa on enzymes related to AD and showed the potential use for further study as a natural medicine for AD treatment on the basis of the bioactive components isolated from H. diffusa.

Iridoid glycosides isolated from Nardostachys chinensis batal with NO production inhibitory activity

Investigation into the chemical diversity of Nardostachys chinensis Batal led to the discovery of three new (1-3) and one known (4) iridoid glycosides. Their structures were established through spectroscopic methods including 1 D and 2 D NMR experiments and HRESIMS analysis. Inhibitory effects of 1-4 on nitric oxide production were investigated in lipopolysaccaride (LPS)-mediated RAW 264.7 cells, and they displayed IC₅₀ values in the range 7.8-15.2 μM.

A new nitrogen-containing iridoid glycoside from lonicera macranthoides

A new nitrogen-containing iridoid glycoside, named (7 R,3'R)-lonijapospiroside A (1), together with thirteen known iridoid glycosides, were isolated from the flower buds of Lonicera macranthoides. The structures of these compounds were established on the basis of spectroscopic analyses. Among them, compounds 1-4 are four diastereoisomers, and their absolute configurations were accurately established by the NOE spectra as well as comparison of their experimental and calculated ECD spectra. The anti-inflammatory activities of all isolates were evaluated by measuring their inhibitory effects on NO, IL-6, and TNF-α production in LPS stimulated RAW 264.7 macrophages. Compound 14 exhibited anti-inflammatory activities by inhibiting IL-6 with an IC₅₀ value of 54.70 μM, comparable to that of the positive control (hydrocortisone, IC₅₀: 62.6 ± 1.7 μM).

Characterization, crystal structure and cytotoxic activity of a rare iridoid glycoside from Lonicera saccata

A new iridoid glycoside, methyl (3R,4R,4aS,7S,7aR)-3-hydroxy-7-methyl-5-oxooctahydrocyclopenta[c]pyran-4-carboxylate-3-O-β-D-(1'S,2'R,3'S,4'S,5'R)-glucopyranoside, named loniceroside A, C₁₇H₂₆O₁₀, (1), was obtained from the aerial parts of Lonicera saccata. Its structure was established based on an analysis of spectroscopic data, including 1D NMR, 2D NMR and HRESIMS, and the configurations of the chiral C atoms were determined by X-ray crystallographic analysis. The single-crystal structure reveals that the cyclopenta[c]pyran scaffold is formed from a five-membered ring and a chair-like six-membered ring connected through two bridgehead chiral C atoms. In the solid state, the glucose group of (1) plays an important role in constructing an unusual supramolecular motif. The structure analysis revealed adjacent molecules linked together through intermolecular O-H...O hydrogen bonds to generate a banded structure. Furthermore, the banded structures are linked into a three-dimensional network by interesting hydrogen bonds. Biogenetically, compound (1) carries a glucopyranosyloxy moiety at the C-3 position, representing a rare structural feature for naturally occurring iridoid glycosides. The growth inhibitory effects against human cervical carcinoma cells (Hela), human lung adenocarcinoma cells (A549), human acute mononuclear granulocyte leukaemia (THP-1) and the human liver hepatocellular carcinoma cell line (HepG2) were evaluated by the MTT method.

A new chlorine-containing iridoid glycoside from Plantago maxima

A phytochemical investigation on the whole plant of Plantago maxima Juss. ex Jacq led to the isolation of a new and rare chlorinated iridoid glycoside named plantomoside (1), along with three known compounds, geniposidic acid (2), 10-deoxygeniposidic acid (3), and viteoid II (4). The structure of 1 was determined through 1 D and 2 D NMR spectroscopic data analysis, HR-ESI-MS, and acid hydrolysis.

Antioxidant Effects of Bioactive Compounds Isolated from Pressurized Steam-Treated Corni Fructus and Their Protective Effects Against UVB-Irradiated HS68 Cells

This study evaluated the antioxidant and protective effects of bioactive compounds isolated from pressurized steam-treated Corni Fructus (PSC). We had previously tested the protective effects of the furan fraction containing 5-hydroxymethylfurfural (5-HMF), polyphenol fraction containing gallic acid, and iridoid glycoside fraction containing morroniside and loganin. We measured the potency of antioxidant activities of the bioactive compounds isolated from PSC via oxygen radical absorbance capacity (ORAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays. One fraction in particular (named F-2) not only contained high amounts of phenolics but also had potent antioxidant activities. The protective effects of F-2 were evaluated by measuring the levels of the collagen-degrading enzyme, matrix metalloproteinase-1 (MMP-1), and the marker of collagen biosynthesis, procollagen type I C-peptide (PIP), in UVB-treated HS68 fibroblasts. MMP-1 levels decreased in an F-2 concentration-dependent manner, and PIP secretion from the cultured HS68 cells was significantly higher than that from the UVB-irradiated cultures alone. Further, F-2 attenuated UVB-induced MMP-1 and ameliorated UVB-downregulated collagen type I alpha 1 mRNA expression in HS68 cells. Therefore, F-2 isolated from PSC is a good candidate for the prevention of skin damage from free radicals in various skin conditions.

[Research progress on metabolism and pharmacological activities of several iridoid glycosides]

As a large category of natural products widely present in traditional Chinese medicine, iridoid glycosides have multiple pharmacological activities. Recent researches suggest that iridoid glycosides mainly exist in vivo in the forms of original form, aglycone and a series of their Ⅰ and Ⅱ metabolites under the biotransformation effect, and their metabolites have been proved to have multiple pharmacological activities. The research progress on in vivo metabolism and metabolite activities of several iridoid glycosides would be reviewed in this article, to provide a theoretical basis for the further development and utilization of iridoid compounds and their metabolites.

Hemiparasites can transmit indirect effects from their host plants to herbivores

Parasitic plants can serve as critical intermediaries between their hosts and other organisms; however these relationships are not well understood. To investigate the relative importance of plant traits in such interactions, we studied the role of the root hemiparasite, Castilleja levisecta (Orobanchaceae), as a mediator of interactions between the host plants it parasitizes and the lepidopteran herbivore Euphydryas editha (Nymphalidae), whose caterpillars feed on Castilleja and sequester iridoid glycosides from it. We tested whether the hemiparasite's size, leaf N concentration, and iridoid glycoside concentrations were influenced by the identity of its host plant, and then whether these traits influenced outcomes for the herbivore. We found that the hemiparasite's size and leaf N depended on the host it parasitized, and these traits in turn affected outcomes for E. editha. Specifically, Euphydryas editha survival increased with hemiparasite size and caterpillar mass increased with leaf N; caterpillars with greater mass were more likely to survive during diapause. We also found preliminary evidence that host identity influenced iridoid glycoside sequestration by the herbivore. Mean iridoid glycoside concentrations in caterpillars ranged from 1-12% depending on the host being parasitized by Castilleja. This study demonstrates that root parasitism can result in strong indirect effects on higher trophic levels, influencing organisms' survival, growth, and chemical interactions.

Phytochemical investigation and acetylcholinesterase inhibitory activity of bark of Hymenodictyon orixense

The chemical investigation of the methanol extract of Hymenodictyon orixense bark, a Thai medicinal herb, provided five compounds. Their structures were identified on the basis of 1D NMR and MS data, as well as by comparison of the data with published values, as an iridoid glycoside: loganin (1), four coumarins: scopoletin (2), scopolin (3), hymexelsin (4) and scopoletin 7-O-β-D-xylopyranosyl-(1→6)-β-D-glucopyranoside (5). Compounds 1-5 showed acetylcholinesterase (AChE) inhibitory activity in the range of 13.92-34.18% at a concentration of 100 μg/mL. In addition, compounds 1 and 5 are reported for the first time from this genus.

A Review on the Phytochemistry, Pharmacology, Pharmacokinetics and Toxicology of Geniposide, a Natural Product

Iridoid glycosides are natural products occurring widely in many herbal plants. Geniposide (C17H24O10) is a well-known one, present in nearly 40 species belonging to various families, especially the Rubiaceae. Along with this herbal component, dozens of its natural derivatives have also been isolated and characterized by researchers. Furthermore, a large body of pharmacological evidence has proved the various biological activities of geniposide, such as anti-inflammatory, anti-oxidative, anti-diabetic, neuroprotective, hepatoprotective, cholagogic effects and so on. However, there have been some research articles on its toxicity in recent years. Therefore, this review paper aims to provide the researchers with a comprehensive profile of geniposide on its phytochemistry, pharmacology, pharmacokinetics and toxicology in order to highlight some present issues and future perspectives as well as to help us develop and utilize this iridoid glycoside more efficiently and safely.

HPLC-ELSD Quantification and Centrifugal Partition Chromatography Isolation of 8-O-Acetylharpagide from Oxera coronata (Lamiaceae)

INTRODUCTION

Iridoid glycosides possess highly functionalised monoterpenoid aglycon with several contiguous stereocentres. For the most common, they are often present in quantities reaching several percentage of the fresh plant weight, and thus they may be regarded as starting material for the synthesis of a number of new chiral and bioactive molecules.

OBJECTIVE

To quantify and to isolate 8-O-acetylharpagide (AH) from several extracts of Oxera coronata R.P.J. de Kok, a Lamiaceae species endemic to New Caledonia, using HPLC-ELSD (evaporative light scattering detector) and centrifugal partition chromatography (CPC).

METHODOLOGY

Oxera coronata produces high amounts of AH in leaves, twigs and fruits. Water and methanol extracts of these plant parts were prepared. The content of AH in each extract was quantified by HPLC-ELSD, using acetonitrile-water (+0.1% formic acid) gradient elution. The HPLC method was validated for precision, linearity, limit of detection (LOD), limit of quantification (LOQ) and accuracy. A ternary solvent system ethyl acetate/n-propanol/water (3:2:5, v/v/v) was selected and applied to recover the target compound using Spot CPC from the leaves aqueous extract.

RESULTS

HPLC-ELSD analysis followed by CPC purification led to the efficient isolation of AH from O. coronata leaves aqueous extract.

CONCLUSION

HPLC-ELSD has proven to be a well-adapted detection and quantification method for iridoid glycosides, while CPC confirmed to be an efficient technique for the isolation of polar compounds. Copyright © 2016 John Wiley & Sons, Ltd.

A new iridoid glycoside from the fruits of Vitex rotundifolia

One new iridoid glycoside, 6',10-di-O-(4-hydroxybenzoyl) aucubin (1), together with ten known compounds, including five diterpenoids (2-6), two triterpene glucosides (7-8) and three methoxylated flavonoids (9-11) were isolated from the fruits of Vitex rotundifolia. Compounds (3, 4, 7, and 8) were reported for the first time from this plant. Their structures were elucidated by spectral analysis and by comparison with literature data. Furthermore, some of the isolated compounds were evaluated for their cytotoxicities against A549 and HepG-2 cell lines using MTT assay, and only compounds 9 and 10 exhibited potent cytotoxic activity with IC₅₀ values of 13 ± 4 and 35 ± 10 μM against HepG-2 cell lines.

Hepatoprotective effects of Gentianella turkestanerum extracts on acute liver injury induced by carbon tetrachloride in mice

Objective: To investigate the contents of secoiridoid compounds (i.e. sweroside, swertiamarin and gentiopicrin) from Gentianella turkestanerum extracts, and the potential effects of G. turkestanerum extracts against carbon tetrachloride (CCl₄) induced liver injury in mice. Methods: The contents of swertiamarin, gentiopicroside and sweroside from different G. turkestanerum extracts were determined with high performance liquid chromatography (HPLC). CCl₄ was used to induce acute liver injury in mice. The serum aspartate amino transferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total protein (TP), total bilirubin (TB), superoxide dismutase (SOD), malondialdehyde (MDA), glutathione transferase (GSH) and catalase (CAT) were measured. HE staining was performed to investigate the pathological changes of liver. Results: Iridoid glycoside showed the highest content in the product extracted by butanol (designated as GBA), but lower in the products extracted by ethyl acetate and water designated as GEA and GW, respectively. All G. turkestanerum extracts showed protective effects against CCl₄ induced acute liver injury in mice, among which GBA showed the maximal protective effects. G. turkestanerum extracts induced significant decrease in the serum ALT, AST, ALP and TB compared with those in the mice with acute lung injury (P < 0.01). Obvious increase was noticed in serum TP (P < 0.01). Moreover, such effects presented in a dose-dependent manner. Compared with the control group, the MDA was significantly elevated in the model group (P < 0.01), while significant decrease was observed in the levels of SOD, GSH and CAT in model group compared with the control group (P < 0.01). Whereas, such phenomenon was completely reversed by G. turkestanerum extracts in a dose-dependent manner. Conclusion:G. turkestanerum showed protective effects against CCl₄ induced acute liver injury in mice.

Systematic separation and purification of iridoid glycosides and crocetin derivatives from Gardenia jasminoides Ellis by high-speed counter-current chromatography

INTRODUCTION

Iridoid glycosides and crocetin derivatives are the main bioactive components of Gardenia. The processes of separation of these compounds reported in much of the literature are tedious, time consuming and require multiple chromatographic steps, which results in lower recovery and higher costs.

OBJECTIVE

To develop a high-speed counter-current chromatography (HSCCC) method for the systematic separation and purification of iridoid glycosides and crocetin derivatives on a preparative scale from Gardenia.

METHODS

After fractionation using HPD100 column chromatography, n-butanol:ethanol:water (10:1:10, v/v) was selected to purify gardenoside, 6β-hydroxy geniposide and geniposidic acid from fraction A; ethyl acetate:n-butanol:water (2:1.5:3, v/v) was used to isolate geniposide from fraction B; crocin-1, crocin-2, crocin-3 and crocin-4 were purified by hexane:ethyl acetate:n-butanol:water (1:2:1:5, v/v) from fraction C. The head-to-tail elution mode was used with a flow rate of 8.0 mL/min and a rotary speed of 600 rpm.

RESULTS

After HSCCC isolation, 151.1 mg of gardenoside, 52.2 mg of 6β-hydroxy geniposide and 24.5 mg of geniposidic acid were obtained from 800 mg of fraction A; 587.2 mg of geniposide was obtained from 800 mg of Fraction B; 246.2 mg of crocin-1, 34.2 mg of crocin-2, 24.4 mg of crocin-3 and 24.7 mg of crocin-4 were obtained from 1000mg of fraction C. Their purities were found by UPLC analysis to be 91.7%, 93.4%, 92.5%, 98.2%, 94.1%, 96.3%, 94.1% and 98.9% respectively.

CONCLUSION

The present results demonstrates that the main iridoid glycosides and crocetin derivatives in Gardenia can be obtained efficiently from extracts using HSCCC.

Enzymatic activation of oleuropein: a protein crosslinker used as a chemical defense in the privet tree

Leaves of the privet tree, Ligustrum obtusifolium, contain a large amount of oleuropein, a phenolic secoiridoid glycoside, which is stably kept in a compartment separate from activating enzymes. When the leaf tissue is destroyed by herbivores, enzymes localized in organelles start to activate oleuropein into a very strong protein denaturant that has protein-crosslinking and lysine-decreasing activities. These activities are stronger than ever reported from plant systems and have adverse effects against herbivores by decreasing the nutritive value of dietary protein completely. We report here that strong oleuropein-specific beta-glucosidase in organelles activates oleuropein by converting the secoiridoid glucoside moiety of oleuropein into a glutaraldehyde-like structure, which is also an alpha,beta-unsaturated aldehyde. Oleuropein activated by beta-glucosidase had very strong protein-denaturing, protein-crosslinking, and lysine-alkylating activities that are very similar to, but stronger than, those of glutaraldehyde. Aucubin, another iridoid glycoside, had similar activities after beta-glucosidase treatment. We also detected polyphenol oxidase activity in organelles that activate the dihydroxyphenolic moiety to have protein-crosslinking activities. These data suggest that the privet tree has developed an effective defense mechanism with oleuropein, a unique multivalent alkylator ideal as a protein-crosslinker. Our results that iridoid glycosides are precursors of alkylators may elucidate the chemical bases that underlie various bioactivities and ecological roles of iridoid glycosides.