Molecular modeling of non-covalent binding of Ligustrum lucidum secoiridoid glucosides to AP-1/matrix metalloproteinase pathway components.

Ligustrum lucidum secoiridoid glucosides have been demonstrated to treat various types of diseases such as inflammation, pain, hepatotoxicity and hyperlipidermic as well as tonic for liver and kidney. Matrix metalloproteinases (MMPs) play a key role upon the pathology of photoaging. The present computational study showed that among the six secoiridoid glucosides (ligustroside, lucidumoside A, lucidumoside C, neonuezhenide, oleoside dimethylester, and oleuropein), ligustroside and lucidumoside A competitively inhibit all MMP-1, MMP-3, and MMP-9 activities in the docking models. The molecular docking analysis revealed a network of interactions between MMP-1, MMP-3, and MMP-9 and the ligands; ligustroside and lucidumoside A, and oxygen-containing and hydrophobic functional groups appear to be responsible for these enhanced interactions. The effect of ligustroside and lucidumoside A on the transcription factor AP-1 action was also investigated using molecular docking and dynamics simulations. The experiments suggested that inhibition of an AP-1-DNA complex formation could be on account of the direct interference of AP-1 binding onto the DNA binding sequence by ligustroside and lucidumoside A. The results suggest that both compounds have the highest potential for application as an anti-aging agent with the MMP inhibitory and anti-transcriptional activities.

An HPLC method for simultaneous quantitative determination of seven secoiridoid glucosides separated from the roots of Ilex pubescens.

A simple and specific high-performance liquid chromatographic method has been developed and validated to simultaneously determine seven secoiridoid glucosides for the first time. Three of them were separated from the ethanolic extract of the roots of Ilex pubescens for the first time, namely nuezhenide A, ligusides B and oleonuezhenide. In quantitative analysis, all of the calibration curves showed good linear regression (r > 0.999) within the tested ranges, and the mean recoveries of three different concentrations ranged from 97.6 to 101.2%. The limit of detection and limit of quantification were <4.18 and 11.63 ng mL-1 , respectively. The relative standard deviation for repeatability and the precision of seven analytes were <3.4 and 1.9%, respectively. The established method was successfully applied to simultaneous determination of seven secoiridoid glucosides in 11 batches of samples collected from different habitats in China.

Anti-inflammatory secoiridoid glycosides from Gentianella azurea.

A phytochemical investigation on crude extract of Gentianella azurea led to the isolation of ten new (1-10) and one known (11) secoiridoid glycosides. Their structures were unambiguously elucidated by analysis of 1D and 2D NMR. Compounds 2, 5 and 11 were found to inhibit nitric oxide (NO) production in RAW 264.7 macrophages with IC50 values of 52.78 ± 8.61, 0.69 ± 0.23 and 5.18 ± 1.33, respectively, while indomethacin, the positive control, showed an IC50 value of 1.25 ± 0.52 µM.

Functional Characterization of Genes Coding for Novel ß-D-Glucosidases Involved in the Initial Step of Secoiridoid Glucosides Catabolism in Centaurium erythraea Rafn.

Secoiridoid glucosides (SGs) are monoterpenoids derived from the iridoid cyclopentane-C-pyran skeleton with ß-D glucose linked at C1 position. Coordinated metabolic processes, such as biosynthesis and catabolism of SGs, ensure constitutive presence of these bitter tasting compounds in plant tissues, which plays a decisive role in the defense against pathogens and herbivores. These compounds are susceptible to hydrolysis mediated by enzymes ß-glucosidases, and the resulting aglycones are subsequently directed toward different metabolic pathways in plants. Function of two ß-D-glucosidases (named CeBGlu1 and CeBGlu2) from centaury (Centaurium erythraea Rafn; fam. Gentianaceae), belonging to the glycoside hydrolase 1 (GH1) family, was confirmed using in vitro assays with recombinant proteins, following their heterologous expression in E. coli and His-tag affinity purification. Although they show slightly differential substrate preference, both isoforms display high specificity toward SGs and the organ-specific distribution of transcripts was positively correlated with the content of SGs in diploid and tetraploid C. erythraea plants. Transient overexpression of CeBGlu1 and CeBGlu2 in C. erythraea leaves induced changes in metabolite profiles. The effectiveness of transgene overexpression has been altered by plant ploidy. UHPLC/DAD/(±)HESI - MS2 profiling of leaves of diploid and tetraploid C. erythraea genotypes revealed that the amounts of major SGs; sweroside, swertiamarin, and gentiopicrin was decreased in agroinfiltrated leaves, especially when CeBGlu1 and CeBGlu2 were co-expressed with transgene silencing suppressor p19. The work demonstrates that in planta metabolic engineering adopting transient overexpression of CeBGlu1 and CeBGlu2 is a suitable tool for the modulation of SGs content and glucosides/aglycones ratio, which might have substantial effects on overall phytochemistry of C. erythraea.

New Oleanane-type glycosides and secoiridoid glucoside from Aptandra zenkeri.

Four new saponins, camelliagenin A and B derivatives, and one new secoiridoid glucoside were isolated from the stem bark of Aptandra zenkeri Engl. (Aptandraceae) together with two known secoiridoid glucosides. Their structures were determined based on a combination of 1D- and 2D-NMR experiments techniques and HR-ESI-MS analysis. This is the first report on saponins in genus Aptandra.

Secoiridoids Metabolism Response to Wounding in Common Centaury (Centaurium erythraea Rafn) Leaves.

Centaurium erythraea Rafn produces and accumulates various biologically active specialized metabolites, including secoiridoid glucosides (SGs), which help plants to cope with unfavorable environmental conditions. Specialized metabolism is commonly modulated in a way to increase the level of protective metabolites, such as SGs. Here, we report the molecular background of the wounding-induced changes in SGs metabolism for the first time. The mechanical wounding of leaves leads to a coordinated up-regulation of SGs biosynthetic genes and corresponding JA-related transcription factors (TFs) after 24 h, which results in the increase of metabolic flux through the biosynthetic pathway and, finally, leads to the elevated accumulation of SGs 96 h upon injury. The most pronounced increase in relative expression was detected for secologanin synthase (CeSLS), highlighting this enzyme as an important point for the regulation of biosynthetic flux through the SG pathway. A similar expression pattern was observed for CeBIS1, imposing itself as the TF that is prominently involved in wound-induced regulation of SGs biosynthesis genes. The high degree of positive correlations between and among the biosynthetic genes and targeted TFs expressions indicate the transcriptional regulation of SGs biosynthesis in response to wounding with a significant role of CeBIS1, which is a known component of the jasmonic acid (JA) signaling pathway.

Iridoid glucosides in the genus Sutera (Scrophulariaceae) as chemotaxonomic markers in tribe Limoselleae.

From two species of Sutera (S. foetida and S. cordata) (Scrophulariaceae tribe Limoselleae) were isolated three known secoiridoid glucosides (12-14) as well as four iridoid congeners (8-11), all biosynthetically derived from iridodial glucoside (and/or deoxyloganic acid). In addition, two previously unknown compounds were found, namely a terpenoid glucoside lactone (suterolide, 21) and the phenylethanoid glycoside 2''''-O-acetyl-angoroside A (19) as well as verbascoside, echinacoside and tubuloside A(15-17, respectively). Two other species, Jamesbrittenia dissecta and Lyperia antirrhinoides, previously considered to belong to the same genus (Sutera) were shown to be members of two different genera, respectively. Significantly, these two species contained iridoids derived from 8-epi-iridodial (and 8-epideoxyloganic acid), namely aucubin (2), melittoside (3) and acetylharpagide (4). In addition we investigated Melanospermum transvaalense, Lyperia tristis and Microdon dubius likewise from Limoselleae and all of these contained iridoid glucosides from the 8-epi-pathway. Thus, secoiridoid distribution confirms the DNA-based circumscription of Sutera and its sister-group relationship with Manulea. In addition, the results show that the clade including these two genera has a biosynthetic pathway to iridoids fundamentally different from the rest of the tribe and from the whole family Scrophulariaceae.

Two new secoiridoid glucosides and a new lignan from the roots of Ilex pubescens.

Two new secoiridoid glucosides, ilexpublignoside (1), pubzenoside (2), and a new lignan, ilexlignan B (3), along with seven known compounds (4-10) were isolated from the roots of Ilex pubescens for the first time. Their chemical structures were elucidated on the basis of extensive spectroscopic methods, including IR, UV, HR-ESI-MS, CD, NMR experiments, as well as comparison with the reported data.

Hepatoprotective standardized EtOH-water extract from the seeds of Fraxinus rhynchophylla Hance.

Fraxinus rhynchophylla Hance (Oleaceae), its stem barks are known as Cortex fraxini ( qín pí) listed in Chinese Pharmacopoeia. Phytochemical study has indicated that methanol extracts from Qinpi has protective effect on acute liver injury. The present study investigates the hepatoprotective activity of EtOH-water extract from the seeds of F. rhynchophylla Hance against carbon tetrachloride-induced liver injury in mice. The EtOH-water extract significantly alleviated liver damage as indicated by the decreased levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST), the malondialdehyde (MDA) content, and increased the levels of superoxide dismutase (SOD), glutathione (GSH) and glutathione peroxidase (GSH-Px), and reduced the pathological tissue injury induced by CCl4. Quantitative analysis of seven major constituents (1-7) in EtOH-water extract (EWE) was developed by high performance liquid chromatography-diode-array detector (HPLC-DAD). The current research indicates that the EWE from the seeds of F. rhynchophylla Hance decreased liver index, inhibited the increase of serum aminotransferase induced by CCl4, and decreased hepatic MDA content, SOD and GSH-Px activities. These results suggested that the pretreatment with EWE protected mice against CCl4-induced liver injuries. Based on the results, the EtOH-water extract from the seeds of F. rhynchophylla Hance is efficacious for prevention and treatment of CCl4-induced hepatic injury in mice. Secoiridoid and tyrosol glucosides might be the active ingredients responsible for the biological and pharmacological activities of hepatoprotection.

Iridoid glucosides in the endemic Picconia azorica (Oleaceae).

In our continued investigation of plants from the family Oleaceae we have now investigated Picconia azorica endemic to the Azores. Like most species within the family it contains the oleoside-based secoiridoid glucosides ligstroside and oleuropein as the main compounds and in addition verbascoside and echinacoside. As with the previously investigated Picconia excelsa, it also contained the carbocyclic iridoid glucosides involved in the biosynthetic pathway to the oleoside derivatives. However, while P. excelsa contained loganin esterified with some monoterpenoid acids, P. azorica contains similar esters of 7-epi-loganic acid named Picconioside A and B. In addition were found the two 7-O-E/Z-cinnamoyl esters of 7-epi-loganic acid named Picconioside C and D.

Further iridoid glucosides in the genus Manulea (Scrophulariaceae).

From Manulea altissima (Scrophulariaceae) were isolated five known secoiridoid glucosides sweroside, eustomoside, eustoside, secoxyloganin and secologanoside as well as the 4″-O-rhamnopyranosyl-feruloyl ester of adoxosidic acid, named altissimoside. Also, the caffeoyl phenylethanoid glycoside verbascoside was isolated. In addition two previously unknown terpenoid esters of 6ß-hydroxy 8-epi-boschnaloside, named manucoside A and B were isolated from a formerly obtained fraction from the work-up of Manulea corymbosa. The distribution of iridoid glucosides in the Scrophulariaceae is discussed.