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.

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.

Neuroprotective Effects of Aucubin against Cerebral Ischemia and Ischemia Injury through the Inhibition of the TLR4/NF-κB Inflammatory Signaling Pathway in Gerbils.

Aucubin, an iridoid glycoside, possesses beneficial bioactivities in many diseases, but little is known about its neuroprotective effects and mechanisms in brain ischemia and reperfusion (IR) injury. This study evaluated whether aucubin exhibited neuroprotective effects against IR injury in the hippocampal CA1 region through anti-inflammatory activity in gerbils. Aucubin (10 mg/kg) was administered intraperitoneally once a day for one week prior to IR. Neuroprotective effects of aucubin were assessed by neuronal nuclei (NeuN) immunofluorescence and Floro-Jade C (FJC) histofluorescence. Microgliosis and astrogliosis were evaluated using immunohistochemistry with anti-ionized calcium binding adapter protein 1 (Iba1) and glial fibrillary acidic protein (GFAP). Protein levels of proinflammatory cytokines interleukin1 beta (IL1ß) and tumor necrosis factor alpha (TNFα) were assayed using enzyme-linked immunosorbent assay and Western blot. Changes in toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) signaling pathway were assessed by measuring levels of TLR4, inhibitor of NF-κB alpha (IκBα), and NF-κB p65 using Western blot. Aucubin treatment protected pyramidal neurons from IR injury. IR-induced microgliosis and astrogliosis were suppressed by aucubin treatment. IR-induced increases in IL1ß and TNFα levels were significantly alleviated by the treatment. IR-induced upregulation of TLR4 and downregulation of IκBα were significantly prevented by aucubin treatment, and IR-induced nuclear translocation of NF-κB was reversed by aucubin treatment. Briefly, aucubin exhibited neuroprotective effects against brain IR injury, which might be related to the attenuation of neuroinflammation through inhibiting the TLR-4/NF-κB signaling pathway. These results suggest that aucubin pretreatment may be a potential approach for the protection of brain IR injury.

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.

Cornus iridoid glycoside alleviates sepsis-induced acute lung injury by regulating NF-κB and Nrf2/HO-1 pathways.

BACKGROUND: Sepsis-induced acute lung injury (ALI) is a syndrome associated with inflammation. Cornus iridoid glycoside (CIG), a bioactive component isolated from Corni Fructus, exhibits anti-inflammatory activities. However, the function and underlying mechanisms of CIG in mice with sepsis-induced ALI remain elusive. METHODS: The sepsis-elicited ALI model of mice was established by the induction of cecal ligation and puncture (CLP). The wet/dry (W/D) ratio of lung tissues was examined, and the pathological alterations were determined by hematoxylin and eosin staining. The messenger RNA (mRNA) expressions and serum levels of Interleukin (IL)-1ß, IL-6, and tumor necrosis factor-α (TNF-α) were measured by reverse transcription-quantitative polymerase chain reaction and enzyme-linked immunosorbent serologic assay, respectively. The concentrations of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) were assessed by biochemical kits. In addition, the relative protein levels of p-p65, p65, phosphorylated- nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (p-IκBα), IκBα, nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1) gene were analyzed by Western blotting analysis. RESULTS: CLP enhanced W/D ratio and aggravated pathological changes and scores in mice, which were obviously alleviated by the two concentrations of CIG treatment. CIG treatment notably decreased the CLP-induced mRNA expressions and serum levels of IL-1ß, IL-6, TNF-α, and MDA, but enhanced the decreased concentrations (caused by CLP) of SOD and GSH-Px. Moreover, CIG treatment significantly decreased the ratios of p65/p-p65 and IκBα/p-IκBα caused by CLP, but aggravated the CLP-induced relative protein levels of Nrf2 and HO-1. CONCLUSIONS: CIG obviously ameliorated the sepsis-induced ALI in mice by suppressing inflammation and oxidative stress, which was closely associated with nuclear factor kappa B (NF-κB) and Nrf2-HO-1 signaling pathways.

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.

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.

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.

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 ß-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.

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.

Protective Effects of Cornel Iridoid Glycoside in Rats After Traumatic Brain Injury.

Cornel iridoid glycoside (CIG) is the active ingredient extracted from Cornus officinalis. Our previous studies showed that CIG had protective effects on several brain injury models. In the present study, we aimed to examine the effects and elucidate the mechanisms of CIG against traumatic brain injury (TBI). TBI was induced in the right cerebral cortex of male adult rats. The neurological and cognitive functions were evaluated by modified neurological severity score (mNSS) and object recognition test (ORT), respectively. The level of serum S100ß was measured by an ELISA method. Nissl staining was used to estimate the neuron survival in the brain. The expression of proteins was determined by western blot and/or immunohistochemical staining. We found that intragastric administration of CIG in TBI rats ameliorated the neurological defects and cognitive impairment, and alleviated the neuronal loss in the injured brain. In the acute stage of TBI (24-72 h), CIG decreased the level of S100ß in the serum and brain, increased the ratio of Bcl-2/Bax and decreased the expression of caspase-3 in the injured cortex. Moreover, the treatment with CIG for 30 days increased the levels of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), enhanced the expression of synapsin I, synaptophysin and postsynaptic density protein 95 (PSD-95), and inhibited the apoptosis-regulating factors in the chronic stage of TBI. The present study demonstrated that CIG had neuroprotective effects against TBI through inhibiting apoptosis in the acute stage and promoting neurorestoration in the chronic stage. The results suggest that CIG may be beneficial to TBI therapy.

Synthetic analogues of durantoside I from Citharexylum spinosum L. and their cytotoxic activity.

New iridoid glycoside derivatives from durantoside I, the latter from the dried flowers and leaves of Citharexylum spinosum, were synthesized by variously modifying a sugar moiety by silylation or acetylation and/or removal of cinnamate group at C-7 position and subsequent screening for comparative cytotoxicity against several cancer cell lines. Addition of alkylsilane to durantoside I and removal of cinnamate group were most effective in improving cytotoxicity.

[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.

Nardonaphthalenones A and B from the roots and rhizomes of Nardostachys chinensis Batal.

Nardonaphthalenones A and B (1-2), one new apo-α-carotenone (3) and four new monoterpenoids (4, 8-9 and 11), along with six known compounds (5-7, 10, 12-13) were isolated from the dried roots and rhizomes of Nardostachys chinensis Batal. Their structures were elucidated by analysis of the spectroscopic data including NMR, HRESIMS and circular dichroism data. Furthermore, the serotonin transporter (SERT)-regulating activities of these isolates were evaluated, among them compound 3 showed the strongest enhancement activity while compound 12 showed a moderate inhibition activity on SERT.

Localization of Defensive Chemicals in Two Congeneric Butterflies (Euphydryas, Nymphalidae).

Many insect species sequester compounds acquired from their host plants for defense against natural enemies. The distribution of these compounds is likely to affect both their efficacy as defenses, and their costs. In this study we examined the distribution of sequestered iridoid glycosides (IGs) in two congeneric species of nymphalid butterfly, Euphydryas anicia and E. phaeton, and found that the pattern of localization of IGs differed between the two species. Although IG concentrations were quite high in the heads of both species, the relative concentrations in wings and abdomens differed substantially. Euphydryas anicia had relatively high IG concentrations in their abdomens and low IG concentrations in their wings, whereas the reverse was true in E. phaeton. We interpret these results in light of two current hypotheses regarding where sequestered chemicals should be localized: that they should be found in wings, which would allow non-lethal sampling by predators; and that their distribution is constrained by the distribution of tissue types to which sequestered compounds bind. We also offer the third hypothesis, that costs of storage may differ among body parts, and that the localization of compounds may reflect a cost-reduction strategy. Results from E. phaeton were consistent with all three of these non-mutually exclusive hypotheses, whereas results from E. anicia were only consistent with the notion that tissue bias among body parts plays a role in IG distribution. The finding that these two congeneric butterflies exhibit different patterns of IG localization suggests that they have been shaped by different selection regimes.

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 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.

[Simultaneous determination of ten major compounds including iridoid glycosides and phenolic acids in Pterocephalus hookeri by UPLC-PDA].

This study is to develop an UPLC-PDA method for determination of 10 major components in Pterocephalus. The UPLC-PDA assay was performed on a Waters Acquity UPLCR BEH C18（2.1 mm ×100 mm,1.7 µm）, and the column temperature was at 30 ℃. The mobile phase consists of water containing 0.2% phosphoric acid (A) and acetonitrile (B) in gradient elution at a flow rate of 0.4 mL•min⁻¹. The detection wave length was set at 237 and 325 nm, and the injection volume was 1 µL in the UPLC system. The linear range of 10 detected compounds were good (r≥0.999 7), and the overall recoveries ranged from 96.30% to 103.0%, with the RSD ranging from 0.72% to 2.9%. The method was simple, accurate and reproducible, which can be used for the simultaneous determination of the content of ten major components in P. hookeri.

Inhibitory effects of harpagoside on TNF-α-induced pro-inflammatory adipokine expression through PPAR-γ activation in 3T3-L1 adipocytes.

Obesity is closely associated with increased production of pro-inflammatory adipokines, including interleukin (IL)-6, plasminogen activator inhibitor (PAI)-1, and adipose-tissue-derived monocyte chemoattractant protein (MCP)-1, which contribute to chronic and low-grade inflammation in adipose tissue. Harpagoside, a major iridoid glycoside present in devil's claw, has been reported to show anti-inflammatory activities by suppression of lipopolysaccharide (LPS)-induced production of inflammatory cytokines in murine macrophages. The present study is aimed to investigate the effects of harpagoside on both tumor necrosis factor (TNF)-α-induced inflammatory adipokine expression and its underlying signaling pathways in differentiated 3T3-L1 cells. Harpagoside significantly inhibited TNF-α-induced mRNA synthesis and protein production of the atherogenic adipokines including IL-6, PAI-1, and MCP-1. Further investigation of the molecular mechanism revealed that pretreatment with harpagoside activated peroxisome proliferator-activated receptor (PPAR)-γ. These findings suggest that the clinical application of medicinal plants which contain harpagoside may lead to a partial prevention of obesity-induced atherosclerosis by attenuating inflammatory responses.