Iridoid Aglycones Research Articles

A temperature-regulated bioorthogonal reaction to target lysine: Hemiacetal pharmacophore in genipin irreversibly binds with UCP2, inhibiting mitochondrial thermogenesis

Mitochondria are essential for eukaryotic life as powerhouses for energy metabolism. Excessive mitochondrial hyperthermia and reactive oxygen species (ROS) production have been associated with aging, cancer, neurodegenerative diseases, and other disorders. Uncoupling protein 2 (UCP2) is the effector responsible for regulating cellular thermogenesis and ROS production via dissipating protons in an electrochemical gradient. A UCP2 inhibitor named genipin (GNP) is being researched for its effect on mitochondrial temperature, but little is known about its mechanisms. This study developed several molecular probes to explore the interactions between GNP and UCP2. The result indicated that the hemiacetal structure in GNP could selectively react with the ɛ-amine of lysine on the UCP2 proton leakage channel through ring-opening condensation at the mitochondrial, cellular, and animal levels. A notable feature of the reaction is its temperature sensitivity and ability to conjugate with UCP2 at high fever as lysine-specific covalent inhibitors that prevent mitochondrial thermogenesis. The result not only clarifies the existence of an antipyretic properties of GNP via its irreversible coupling to UCP2, but also reveals a bioorthogonal reaction of hemiacetal iridoid aglycone for selectively binding with the ɛ-amine of lysine on proteins.

A new iridoid skeleton from Galium asparagifolium and biological activity studies

This study identifies the detailed phytochemical content and biological effects of Galium asparagifolium, for the first time and gained one new iridoid aglycone (1), seven known iridoid glycosides (2–8), two flavonoids (9–10), and one carbohydrate derivative (11) to the literature. The 1D-, 2D- NMR analyses and ESI-Mass allowed us to resolve the structure of new compound as (1S,4aS,​​8aS)-pyrano[4,​3-​c]​pyran-1,​4a,​5,​7,​8,​8a-​hexahydro-​1-​hydroxy-​3-(​2-​hydroxyethyl)-​8-​methyl-8-​carboxylic acid namely galiumic acid. The compounds 1–11 and extracts from G. asparagifolium were investigated in terms of cytotoxic activity by MTT assay, antioxidant activity by DPPH method and antimicrobial activity by DDT and BMM methods. While all compounds and extracts did not show remarkable cytotoxicity, they had variable antimicrobial activities for a variety of gram-positive/gram-negative bacteria and yeast strains. Besides that, most of the compounds showed antioxidant effect with a wide range of DPPH% inhibition values. The structure of the new compound was also elucidated by some computational studies.

Antimicrobial and Immunomodulating Activities of Two Endemic Nepeta Species and Their Major Iridoids Isolated from Natural Sources.

Two Balkan Peninsula endemics, Nepeta rtanjensis and N. argolica subsp. argolica, both characterized by specialized metabolite profiles predominated by iridoids and phenolics, are differentiated according to the stereochemistry of major iridoid aglycone nepetalactone (NL). For the first time, the present study provides a comparative analysis of antimicrobial and immunomodulating activities of the two Nepeta species and their major iridoids isolated from natural sources—cis,trans-NL, trans,cis-NL, and 1,5,9-epideoxyloganic acid (1,5,9-eDLA), as well as of phenolic acid rosmarinic acid (RA). Methanol extracts and pure iridoids displayed excellent antimicrobial activity against eight strains of bacteria and seven strains of fungi. They were especially potent against food-borne pathogens such as L. monocytogenes, E. coli, S. aureus, Penicillium sp., and Aspergillus sp. Targeted iridoids were efficient agents in preventing biofilm formation of resistant P. aeruginosa strain, and they displayed additive antimicrobial interaction. Iridoids are, to a great extent, responsible for the prominent antimicrobial activities of the two Nepeta species, although are probably minor contributors to the moderate immunomodulatory effects. The analyzed iridoids and RA, individually or in mixtures, have the potential to be used in the pharmaceutical industry as potent antimicrobials, and in the food industry to increase the shelf life and safety of food products.

Iridoids from Vitex negundo var. heterophylla and their antioxidant activities

Two new iridoids (1-2) together with eight known iridoid glycosides (3-10) were isolated from the 70% EtOH extract of the dried leaves of Vitex negundo var. heterophylla. Their structures were elucidated by extensive spectroscopic analyses. Iridoid aglycones were found for the first time from this plant. All of these compounds were tested for their antioxidant activities. Among them, compound 9 showed moderate radical-scavenging effect on the stable free radical, 1,1-diphenyl-2-picrylhydrazyl, with IC50 values of 26.95 μM.

Iridoid aglycones from the underground parts of Lathraea squamaria

Two epimeric pairs of iridoid aglycones (1a, 1b, 2a, and 2b) were isolated from the underground parts of Lathraea squamaria L. (Orobanchaceae) in a phytochemical study. Their structures were elucidated by UV, 1D and 2D NMR, and comparison with data in the literature. This is the first report of the isolation of these compounds from the species L. squamaria and the family Orobanchaceae. The chemophenetic significance and possible reasons for the occurrence of such iridoid aglycones in holoparasitic plants are discussed.

Simultaneous determination of multiple compounds of Da-Huang-Xiao-Shi decoction in rat plasma by LC-MS/MS and its application in a pharmacokinetic study

Da-Huang-Xiao-Shi decoction (DHXSD), a traditional Chinese medicinal formula, has been used mainly to treat jaundice for more than 1700 years in China. In this study, we developed a rapid, sensitive, and accurate LC–MS/MS method to simultaneously determine multiple, potentially bioactive compounds of DHXSD, including five alkaloids (berberine, phellodendrine, palmatine, jatrorrhizine, and magnoflorine), five anthraquinones (rhein, aloe-emodin, emodin, chrysophanol, and physcion), two iridoid glycosides (geniposide and genipin 1-gentiobioside), and one iridoid aglycone (genipin) in rat plasma. Plasma samples collected from rats were treated immediately with 5% acetic acid to avoid the degradation of genipin. After protein precipitation with acetonitrile containing 5% acetic acid, the compounds were reconstituted in acetonitrile–water (50:50, v/v) solution containing 6.5% formic acid and separated on the ACQUITY™ UPLC BEH C18 column (2.1 × 100 mm; 1.7 μm) using a mobile phase composed of 2 mM ammonium formate in water (solvent A) and acetonitrile (solvent B) at a flow rate of 0.3 mL/min. Quantitation was performed on a Triple Quand 5500 tandem mass spectrometer coupled with an electrospray ionization (ESI) source. Multiple reaction monitoring (MRM) was used to quantify compounds in positive and negative ion modes. The method validation results showed that the specificity, linearity, precision and accuracy, recovery, matrix effect, and stability of the 13 compounds met the requirements for their quantitation in biological samples. This newly established method was successfully used in a pharmacokinetic study on rats orally treated with DHXSD. Besides, glucuronide and sulfate metabolites were also determined in rat plasma after hydrolysis. This is the first method developed for the simultaneous quantification of multiple compounds of DHXSD in vivo. Our study provides relevant information on the pharmacokinetics of DHXSD and the relationship between the compounds of DHXSD and their therapeutic effects.

PO-385 Genetical inhibition of IRE1α in macrophages suppresses hepatocellular carcinoma growth

IntroductionThe microenvironment of hepatocellular carcinoma (HCC) will be synchronised to tumor-promoting niche by the cytokine and growth factors produced by infiltrated inflammatory cells. Macrophages, in particular, have been regarded as the inflammatory effector in HCC. Inositol-requiring enzyme 1α (IRE1α) is an unfolded protein response sensor, that controls protein regulation, metabolism and inflammation. Inhibition of IRE1α has been reported to inhibit metabolic inflammation through macrophages modulation. Therefore, the aim of this study is to investigate the role of IRE1α in tumour associated macrophages of HCC.Material and methodsBone marrow isolated mononuclear cells were differentiated by either culturing with M-CSF or tumour supernatant for 7 days. Expressions of mRNAs was detected by quantitative real time PCR; protein expression was detected by immunoblotting assay; gene silencing was performed by RNA interference. HCC proliferation was detected by BrDU incorporation assay. The animal model was established by implanting subcutaneous grown tumour cube to left lobe of mouse liver. The hepatic tumour growth was monitored by in vivo luciferase imaging system.Results and discussionsWe observed pharmacological inhibition of IRE1α by genipin, an iridoid aglycone reduced expressions of inflammatory factors such as CCR2, TNFα, CCL5, iNOS and IL6 on tumour supernatant-cultured and M-CSF induced macrophages. LPS-induced inflammatory gene expression in macrophages was similarly suppressed by genipin treatment. The role of IRE1α was confirmed from the observation of suppression of all the inflammatory mediators in IRE1α silencing macrophages. Furthermore, co-incubation of HCC cells with IRE1α silencing macrophages inhibited HCC cells proliferation. Our further in vivo study showed suppression of orthotopic HCC tumour growth after genipin intervention. We observed reduced IRE1α expression in hepatic macrophages after genipin treatment. This was accompanied with consistent reduction of inflammatory markers on the sorted hepatic macrophages.ConclusionAltogether, our findings unveil the role of IRE1α in modulating inflammation in macrophages and pharmacological or genetical inactivation of IRE1α in macrophages suppressed HCC progression.

An iridoid glucoside and the related aglycones from Cornus florida.

A new iridoid glucoside, cornusoside A (1), and four new natural product iridoid aglycones, cornolactones A–D (2–5), together with 10 known compounds were isolated from the leaves of Cornus florida. The structures of compounds 1–5 were established by interpretation of their spectroscopic data. Cornolactone B (3) is the first natural cis-fused tricyclic dilactone iridoid containing both a five- and a six-membered lactone ring. A biosynthesis pathway is proposed for cornolactones C (4) and D (5), the C-6 epimers of compounds 1–3.

Iridoids from the flowers of Gardenia jasminoides Ellis and their chemotaxonomic significance

Phytochemical investigation of the flowers of Gardenia jasminoides Ellis (Rubiaceae Gardenia) resulted in the isolation and identification of four iridoid aglycones (1–4) and eleven iridoid glycosides (5–15). This is the first report of the occurrence of these compounds in the genus Gardenia: garjasmine (1), dunnisin (2), α-gardiol (3), β-gardiol (4), diffusoside A (6), diffusoside B (7), genameside C (13), and deacetylasperulosidic acid (14). The chemotaxonomic significance and biosynthetic pathways of these iridoid aglycones (1–4) and iridoid glycosides (5–15) are summarized. Iridoid aglycones and iridoid glycosides are considered as important chemotaxonomic markers in Rubiaceae and this work indicates that the iridoid aglycones (1–4) have a limited distribution in the Rubiaceae.

One-enzyme catalyzed simultaneous plant cell disruption and conversion of released glycoside to aglycone combined with in situ product separation as green one-pot production of genipin from gardenia fruit

A direct one-pot production of genipin, an iridoid aglycone, from crude gardenia fruit was developed. The method relied on the use of single cellulase to disrupt plant cells and to cleave off sugar molecules simultaneously, thereby enhancing the release of intracellular iridoids and converting geniposide to genipin. During the biocatalysis, eco-friendly ethyl acetate was used to extract the product, providing the partial purification and the minimization of genipin degradation. By using 10mg/mL cellulase and 24h-incubation at 50°C, pH 4, combined with in situ extraction, genipin with good purity was yielded at 58.83mg/g, which increased 12.38 and 1.72 times compared with those obtained from the procedures without either the aid of enzyme or in situ extraction, respectively. Therefore, this integrated approach is promising for the production of genipin and should be potentially applied to the preparation of other plant aglycones.

Centrifugal partition chromatography - ECO-friendly method for the multigram purification of aucubin and aucubigenin

Aucubin 1, isolated by Bourquelot and Herissey in 1902, is secondary plant metabolite which can be extracted in large amounts from the fresh aerial parts of Aucuba japonica Thunb.. We have showed that this iridoid serves as an excellent starting chiral material in semisynthetic purposes. In this respect we have been interested to develop efficient and fast method of its purification. Multigram water extract can be directly purified by centrifugal partition chromatography using green solvent system based on water and small amounts of non-halogenated solvents. In addition to aucubin 1, biologically related iridoid aglycone, eucommiol 2 and unstable aucubigenin 3, generated by enzymatic cleavage of 1, were isolated in high-purity.

Iridoid-specific Glucosyltransferase from Gardenia jasminoides

Iridoids are one of the most widely distributed secondary metabolites in higher plants. They are pharmacologically active principles in various medicinal plants and key intermediates in the biosynthesis of monoterpenoid indole alkaloids as well as quinoline alkaloids. Although most iridoids are present as 1-O-glucosides, the glucosylation step in the biosynthetic pathway has remained obscure. We isolated a cDNA coding for UDP-glucose:iridoid glucosyltransferase (UGT85A24) from Gardenia jasminoides. UGT85A24 preferentially glucosylated the 1-O-hydroxyl group of 7-deoxyloganetin and genipin but exhibited only weak activity toward loganetin and no activity toward 7-deoxyloganetic acid. This suggests that, in the biosynthetic pathway of geniposide, a major iridoid compound in G. jasminoides, glucosylation occurs after methylation of 7-deoxyloganetic acid. UGT85A24 showed negligible activity toward any acceptor substrates other than iridoid aglycones. Thus, UGT85A24 has a remarkable specificity for iridoid aglycones. The mRNA level of UGT85A24 overlaps with the marked increase in genipin glucosylation activity in the methyl jasmonate-treated cell cultures of G. jasminoides and is related to iridoid accumulation in G. jasminoides fruits.

Mass spectrometry studies of iridoid aglycone derivatives

Mass spectrometry studies of iridoid aglycone derivatives

Inhibitory Potencies of Several Iridoids on Cyclooxygenase‐1, Cyclooxygnase‐2 Enzymes Activities, Tumor Necrosis Factor‐α and Nitric Oxide Production In Vitro

To verify the anti-inflammatory potency of iridoids, seven iridoid glucosides (aucubin, catalpol, gentiopicroside, swertiamarin, geniposide, geniposidic acid and loganin) and an iridoid aglycone (genipin) were investigated with in vitro testing model systems based on inhibition of cyclooxygenase (COX)-1/-2 enzymes, the tumor necrosis factor-α (TNF-α) formation and nitric oxide (NO) production. The hydrolyzed-iridoid products (H-iridoid) with β-gludosidase treatment only showed inhibitory activities, and revealed different potencies, depending on their chemical structures. Without the β-gludosidase treatment, no single iridoid glycoside exhibited any activities. The aglycone form (genipin) also did not show inhibitory activities. To compare anti-inflammatory potency, the inhibitory concentrations (IC50) in each testing system were measured. The hydrolyzed-aucubin product (H-aucubin) with β-gludosidase treatment showed a moderate inhibition on COX-2 with IC50 of 8.83 μM, but much less inhibition (IC50, 68.9 μM) on COX-1 was noted. Of the other H-iridoid products, the H-loganin and the H-geniposide exhibited higher inhibitory effects on COX-1, revealing IC50 values of 3.55 and 5.37 μM, respectively. In the case of TNF-α assay, four H-iridoid products: H-aucubin, H-catalpol, H-geniposide and H-loganin suppressed the TNF-α formation with IC50 values of 11.2, 33.3, 58.2 and 154.6 μM, respectively. But other H-iridoid products manifested no significant activity. Additional experiments on NO production were conducted. We observed that only the H-aucubin exhibited a significant suppression with IC50 value of 14.1 μM. Genipin, an agycone form, showed no inhibitory effects on all testing models, implying the hydrolysis of the glycosidic bond of iridoid glycoside is a pre-requisite step to produce various biological activities.

Studies of iridoid glycosides using liquid chromatography/electrospray ionization tandem mass spectrometry

Fragmentation pathways of five iridoid glycosides have been studied by using electrospray ionization multi-stage tandem mass spectrometry (ESI-MS(n)). The first-stage MS data of the five iridoid glycosides were compared. The MS spectra showed that the adduct ions of iridoid glycosides and the formate anion were diagnostic ions to distinguish iridoid glycosides with a carboxyl group at the C-4 position or an ester group at the C-4 position. The MS fragmentation pathways of the five iridoid glycosides were also studied. Analyzing the product ion spectra of iridoid glycosides, some neutral losses were observed, such as H(2)O, CO(2) and glucose residues, which were very useful for the identification of the functional groups in the structures of iridoid glycosides. Furthermore, specific loss of one molecule of methyl 3-oxopropanoate or 3-oxopropanic acid was firstly discussed, which corresponded to the isomerization of the hemiacetal group in the structure of iridoid aglycone. According to the fragmentation mechanisms and HPLC/MS(n) data, the structures of five iridoid glycosides in a crude extract of Gardenia jasminoisdes fruit have been identified. Three compounds were compared with standards and the other two were identified as shanzhiside and genipin gentibioside by their MS(n) data without standard compounds. In order to further validate the veracity of the deduction, genipin gentiobioside was isolated from the extract of Gardenia jasminoisdes fruit using Purification Factory and was further identified by C- and H-NMR.

Iridoids from Scutellaria albida ssp. albida

Three iridoid glycosides, 6′- O- E- p-coumaroylgardoside ( 1), 6′- O- p- E-coumaroyl-8- epi-loganic acid ( 2) and scutelloside ( 3) were isolated from the aerial parts of Scutellaria albida subsp. albida, in addition to an anomeric mixture in equilibrium of one iridoid aglycone ( 4, 4a), nine iridoid glycosides ( 5– 13), four known phenylethanoid glycosides ( 14– 17), and six known phenolic derivatives ( 18– 23).

Naturally Occurring Iridoids. A Review. Part 1.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Naturally Occurring Iridoids. A Review, Part 1

A compilation of new naturally occurring iridoid glycosides, iridoid aglycones, iridoid derivatives and bis-iridoids reported during 1994-2005 is provided with available physical and spectral data: mp, [alpha]D, UV, IR, 1H- and 13C-NMR as well as natural source with family and references. 418 compounds with 202 references are cited.

Iridoids from Scutellaria albida ssp. albida

Three iridoid glycosides, 6'-O-E-p-coumaroylgardoside (1), 6'-O-p-E-coumaroyl-8-epi-loganic acid (2) and scutelloside (3) were isolated from the aerial parts of Scutellaria albida subsp. albida, in addition to an anomeric mixture in equilibrium of one iridoid aglycone (4, 4a), nine iridoid glycosides (5-13), four known phenylethanoid glycosides (14-17), and six known phenolic derivatives (18-23).

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.