Spirostanol Saponins from Flowers of Allium Porrum and Related Compounds Indicating Cytotoxic Activity and Affecting Nitric Oxide Production Inhibitory Effect in Peritoneal Macrophages

Saponins, a diverse group of natural compounds, offer an interesting pool of derivatives with biomedical application. In this study, three structurally related spirostanol saponins were isolated and identified from the leek flowers of Allium porrum L. (garden leek). Two of them were identical with the already known leek plant constituents: aginoside (1) and 6-deoxyaginoside (2). The third one was identified as new component of A. porrum; however, it was found identical with yayoisaponin A (3) obtained earlier from a mutant of elephant garlic Allium ampeloprasun L. It is a derivative of the aginoside (1) with additional glucose in its glycosidic chain, identified by MS and NMR analysis as (2α, 3β, 6β, 25R)-2,6-dihydroxyspirostan-3-yl β-D-glucopyranosyl-(1 → 3)-β-D-glucopranosyl-(1 → 2)-[β-D-xylopyranosyl-(1 → 3)]-β-D-glucopyranosyl]-(1 → 4)-β-D-galactopyranoside, previously reported also under the name alliporin. The leek native saponins were tested together with other known and structurally related saponins (tomatonin and digitonin) and with their related aglycones (agigenin and diosgenin) for in vitro cytotoxicity and for effects on NO production in mouse peritoneal cells. The highest inhibitory effects were exhibited by 6-deoxyaginoside. The obtained toxicity data, however, closely correlated with the suppression of NO production. Therefore, an unambiguous linking of obtained bioactivities of saponins with their expected immunobiological properties remained uncertain.

Archangelolide: A sesquiterpene lactone with immunobiological potential from Laserpitium archangelica

Sesquiterpene lactones are secondary plant metabolites with sundry biological effects. In plants, they are synthesized, among others, for pesticidal and antimicrobial effects. Two such compounds, archangelolide and trilobolide of the guaianolide type, are structurally similar to the well-known and clinically tested lactone thapsigargin. While trilobolide has already been studied by us and others, there are only scarce reports on the biological activity of archangelolide. Here we present the preparation of its fluorescent derivative based on a dansyl moiety using azide-alkyne Huisgen cycloaddition having obtained the two sesquiterpene lactones from the seeds of Laserpitium archangelica Wulfen using supercritical CO₂ extraction. We show that dansyl-archangelolide localizes in the endoplasmic reticulum of living cells similarly to trilobolide; localization in mitochondria was also detected. This led us to a more detailed study of the anticancer potential of archangelolide. Interestingly, we found that neither archangelolide nor its dansyl conjugate did exhibit cytotoxic effects in contrast to the structurally closely related counterparts trilobolide and thapsigargin. We explain this observation by a molecular dynamics simulation, in which, in contrast to trilobolide, archangelolide did not bind into the sarco/endoplasmic reticular calcium ATPase cavity utilized by thapsigargin. Last, but not least, archangelolide exhibited anti-inflammatory activity, which makes it promising compound for medicinal purposes.

Pharmacological intervention with oxidative burst in human neutrophils

In this study we investigated the effect of five therapeutically used drugs and four natural polyphenolic compounds on the mechanism of oxidative burst of human neutrophils concerning their participation in the generation of reactive oxygen species (ROS). The compounds investigated decreased the oxidative burst of whole blood in the rank order of potency: N-feruloylserotonin > quercetin > curcumin > arbutin > dithiaden > carvedilol. The generation of intracellular reactive oxygen species in isolated neutrophils decreased in the same rank order, while carvedilol was ineffective. Scavenging of extracellular oxygen radicals followed the rank order of potency: N-feruloylserotonin > curcumin > quercetin > dithiaden. Arbutin and carvedilol had no effect. All compounds tested increased the activity of caspase-3 in cell-free system indicating a positive effect on apoptosis of neutrophils. Activation of protein kinase C was significantly decreased by dithiaden, curcumin, quercetin and N-feruloylserotonin. Carvedilol, dithiaden, quercetin and arbutin reduced activated neutrophil myeloperoxidase release more significantly compared with their less pronounced effect on superoxide generation The presented results are indicative of pharmacological intervention with neutrophils in pathological processes. Of particular interest was the effect of natural compounds. Intracellular inhibition of oxidative burst in isolated neutrophils by the drugs tested and natural antioxidants has to be further analysed since ROS play an important role in immunological responses of neutrophils.

Trilobolide-steroid hybrids: Synthesis, cytotoxic and antimycobacterial activity

Sesquiterpene lactone trilobolide is a sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) inhibitor, thus depleting the Ins(1,4,5)P3-sensitive intracellular calcium stores. Here, we describe a synthesis of a series of 6 trilobolide-steroids conjugates (estradiol, pregnene, dehydroepiandrosterone, and testosterone). We found that the newly synthesized Tb-based compounds possess different remarkable biological activities. Cancer cell cytotoxicity and preferential selectivity is represented in our study by a Tb-pregnene derivative. The most cytotoxic clickates of estradiol and pregnene were studied by FACS where impact on cell cycle and RNA synthesis was observed; live-cell microscopy revealed the impact on cell organelle morphology particularly endoplasmic reticulum, mitochondria and nucleus. Further, we have studied the estrogenic and androgenic properties of the clickate molecules using cell-based luciferase assays. Finally, antimycobacterial tests revealed that testosterone and estradiol derivatives potentiated the antimycobacterial activity up to IC50 of 10.6μM.

Immunoassay for determination of trilobolide

Trilobolide (Tb) is a pharmacologically interesting sesquiterpene lactone isolated from Laser trilobum (L.) Borkh. Structural relation to a sarco/endoplasmic reticulum Ca²⁺-ATPase inhibitor thapsigargin bring promising prospects for Tb to be used in the development of new anti-cancer drugs. As long as there are still unanswered questions regarding its investigation, a need for novel analytical tools emerge. Since immunoassays serve as one of powerful tools within the investigation of natural products, the development of indirect competitive enzyme-linked immunosorbent assay (ELISA) utilizing coating based on avidin-biotin technology is described. In our set-up of ELISA, newly synthesized biotinylated Tb served as immobilized competitor. Tb-carboxymethyloxime-bovine serum albumin (BSA) and Tb-succinoyl-BSA conjugates were used separately for immunization of rabbits. Two sets of polyclonal antibodies (RAbs) were obtained. Antibodies against Tb-succinoyl-BSA conjugate (RAb No. 206) were chosen as the best. Under optimized conditions, limit of detection and 50% intercept of our ELISA were 849pg/mL and 8.89ng/mL, respectively. The cross-reactivity (CR) was tested on 10 structurally related compounds and CR did not exceed 6.1%. The reproducibility of the system is expressed as intra- and inter-assay coefficients of variation (9.7% and 11.4%, respectively). Based on conducted experiments, we proposed the use of ELISA for quantification of Tb in complex biological matrices such as plant extracts. A method was applied to analyze three extracts obtained from different parts of L. trilobum. Data obtained were compared to those acquired by UHPLC-MS/MS. The concordance between the methods (103-87%) showed the ability of ELISA to quantify Tb.

On the pharmacology of oxidative burst of human neutrophils

The effect of three therapeutically used drugs and five polyphenolic compounds on the mechanism of oxidative burst was compared in whole blood and isolated neutrophils at cellular and molecular level. In 10 microM concentration, the compounds investigated decreased the oxidative burst of whole blood in the rank order of potency: N-feruloylserotonin (N-f-5HT) > curcumin (CUR) > quercetin (QUER) > arbutin (ARB) > resveratrol (RES) > dithiaden (DIT) > carvedilol (CARV) > brompheniramine (BPA). The ratio between the percentage inhibition of extracellular versus intracellular chemiluminescence (CL) followed the rank order QUER > N-f-5HT > RES > CUR > DIT and is indicative of the positive effect of the compounds tested against oxidative burst of neutrophils, demonstrating suppression of reactive oxygen species extracellularly with minimal alteration of intracellular reactive oxygen species (ROS). Activation of protein kinase C was significantly decreased by DIT, CUR, QUER and N-f-5HT. CARV, DIT, QUER and ARB reduced activated neutrophil myeloperoxidase release more significantly compared with the effect on superoxide anion generation. All compounds tested increased the activity of caspase-3 in cell-free system. It is suggested that other regulatory mechanisms than protein kinase C might participate in the inhibition of neutrophil activation with the compounds tested. Different mechanisms are concerned in controlling the assembly of NADPH oxidase and the regulatory role of calcium ions is suggested. Compounds decreasing the amount of extracellular ROS generation, yet affecting but minimally intracellular ROS generation, are promising for further investigation in vivo.

Equol Effectively Inhibits Toxic Activity of Human Neutrophils without Influencing Their Viability

Equol (7,4'-dihydroxy-isoflavan, or 4',7-isoflavandiol) is a chroman derivative produced by intestinal bacteria in response to soy isoflavone intake in some, but not in all, humans. Equol shows strong anti-oxidant, anti-estrogenic, anti-cancerous and anti-inflammatory properties. The antioxidative capacity of equol has recently received considerable attention, and it has been used for preventing and treating several diseases. We investigated the effect of equol on human neutrophils, extra- and intracellular formation of oxidants, the phosphorylation of protein regulating NADPH oxidase and its effect on apoptosis. Neutrophils, isolated from blood from healthy subjects, were tested upon activation with various stimulants, proper for reactive oxygen species (ROS) production and treated by equol. Equol has the ability to reduce the toxic action of neutrophils. With increasing concentrations, equol decreased the amount of oxidants produced by neutrophils both extra- and intracellularly. The phosphorylation of p40(phox) (a component of NADPH oxidase, responsible for the assembly of functional oxidase in intracellular membranes) was reduced in the presence of equol. The experiments showed that equol did not change the number of viable, apoptotic or dead neutrophils significantly in all concentrations used. These results indicate the promising effect of equol in the operation of ROS in different mechanisms in the model of inflammation.

Immunobiological properties of sesquiterpene lactones obtained by chemically transformed structural modifications of trilobolide

Our previous research on immunostimulatory properties of trilobolide and its structurally related natural analogues isolated from Laser trilobum (L.) Borkh., encouraged us to investigate structurally related guaianolides belonging to a specific group of sesquiterpene lactones with characteristic glycol moiety attached to the lactone ring. Ever increasing attention has been paid to certain guaianolides such as thapsigargin and trilobolide for their promising anti-inflammatory, anticancer, anti-infectious and SERCA inhibitory activities. However, due to their alkylation capabilities, they might be cytotoxic. Search for compounds with preserved immunobiological properties and decreased cytotoxicity led us to transform some of their structural features, particularly those related to their side chain functionality. For this reason, we prepared a series of over 20 various deacylated, acyl modified, or relactonized derivatives of trilobolide. The immunobiological effects were screened in vitro using the rat peritoneal cells primed with lipopolysaccharide. Secretion of interferon-γ (IFN-γ), interleukins (IL) IL-1β, IL-6 and tumour necrosis factor-α (TNF-α) were determined by ELISA, and nitric oxide (NO) production by Griess reagent. Relation between the molecular structure and immunobiological activity was investigated. Acetylation at 7-OH and 11-OH positions of the lactone ring, or acyl modification of the guaianolide functionalities (including relactonization) of trilobolide, led to inability to stimulate secretion of cytokines and production of NO. Interestingly, minor structural changes achieved by catalytic hydrogenation or hydrogenolysis retained the original immunoactivity of trilobolide. It can be concluded that several new chemically transformed sesquiterpene lactones resembling the immunobiological properties of trilobolide or thapsigargin were prepared and identified. The implication of the lactone vicinal diol (glycol) moiety, combined with other structure functionality, was confirmed as essential for immune properties of the trilobolide or thapsigargin type of guaianolides.

The effect of exogenous 24-epibrassinolide on the ecdysteroid content in the leaves of Spinacia oleracea L

The aim of this study was to show whether/how the application of exogenous 24-epibrassinolide can affect the content of ecdysteroids in spinach leaves. Brassinosteroids and ecdysteroids, structurally related phytosterols, show effect on a range of processes in plants. Brassinosteroids increase biomass yield in some species, photosynthesis and resistance to stress, and ecdysteroids show effect on proteins responsible for binding of CO2 or water cleavage. The mutual interaction of these sterols in plants is unclear. The UPLC-(+)ESI-MS/MS analyses of extracts of treated and untreated spinach (Spinacia oleracea L.) leaves show that the application of exogenous 24-epibrassinolide does influence the ecdysteroid content in plant tissues. The response differs for the major ecdysteroids and also differs from that for the minor ones and is dependent on the developmental stage of the leaves within the same plant or the 24-epibrassinolide concentration applied.

Trilobolide and related sesquiterpene lactones from Laser trilobum possessing immunobiological properties

Three new and five known sesquiterpene lactones were isolated from the roots of Laser trilobum (L.) Borkh. Chemical identity of the known compounds and structural analysis of the new ones were determined by HR MS and NMR spectroscopy. The two new sesquiterpene lactones: 2-acetoxytrilobolide and 2-hydroxy-10-deacetyltrilobolide belong to the guaianolide type, and the third one, eudeslaserolide, to the biogenetically related eudesmanolide type. Both types, together with their biogenetic precursor of germacranolide type (laserolide) are present in L. trilobum, as well as in the related Laserpitium species. Purposefully selected set of these native sesquiterpene lactones was tested for specific immunobiological properties. The obtained results demonstrate that trilobolide and its acetoxy analog are strong activators of cytokine secretion. On the contrary, the other L. trilobum and Laserpitium siler constituents are only very mild activators, or even inhibitors of the cytokine and nitric oxide production.

The natural stilbenoid pinosylvin and activated neutrophils: effects on oxidative burst, protein kinase C, apoptosis and efficiency in adjuvant arthritis

AIM

To investigate the effects of the naturally occurring stilbenoid pinosylvin on neutrophil activity in vitro and in experimental arthritis, and to examine whether protein kinase C (PKC) activation served as an assumed target of pinosylvin action.

METHODS

Fresh human blood neutrophils were isolated. The oxidative burst of neutrophils was evaluated on the basis of enhanced chemiluminescence. Neutrophil viability was evaluated with flow cytometry, and PKC phosphorylation was assessed by Western blotting analysis. Adjuvant arthritis was induced in Lewis rats with heat-killed Mycobacterium butyricum, and the animals were administered with pinosylvin (30 mg/kg, po) daily for 21 d after arthritis induction.

RESULTS

In isolated human neutrophils, pinosylvin (10 and 100 μmol/L) significantly decreased the formation of oxidants, both extra- and intracellularly, and effectively inhibited PKC activation stimulated by phorbol myristate acetate (0.05 μmol/L). The inhibition was not due to neutrophil damage or increased apoptosis. In arthritic rats, the number of neutrophils in blood was dramatically increased, and whole blood chemiluminescence (spontaneous and PMA-stimulated) was markedly enhanced. Pinosylvin administration decreased the number of neutrophils (from 69 671 ± 5588/μL to 51 293 ± 3947/μL, P=0.0198) and significantly reduced the amount of reactive oxygen species in blood.

CONCLUSION

Pinosylvin is an effective inhibitor of neutrophil activity, and is potentially useful as a complementary medicine in states associated with persistent inflammation.

Naturally appearing N-feruloylserotonin isomers suppress oxidative burst of human neutrophils at the protein kinase C level

N-feruloylserotonin (N-f-5HT) isomers, isolated from seeds of Leuzea carthamoides (Wild) DC, inhibited dose-dependent oxidative burst in human whole blood and isolated neutrophils in vitro, which were measured by luminol- and/or isoluminol-enhanced chemiluminescence in the following rank order of stimuli: PMA > OpZ > calcium ionophore A23187. In isolated neutrophils that were stimulated with PMA, N-f-5HT isomers were effective against extracellular and intracellular reactive oxygen species. Liberation of ATP, analysis of apoptosis, and recombinant caspase-3 activity revealed that N-f-5HT isomers, used in concentrations up to 100 μM, did not alter the viability and integrity of isolated neutrophils. Western blot analysis documented that in concentrations of 10 and 100 μM, N-f-5HT isomers significantly decreased PMA-induced phosphorylation of PKC α/β II. The results suggest that N-f-5HT isomers are an effective, naturally occurring substance with a potent pharmacological effect on the oxidative burst of human neutrophils. It should be further investigated for its pharmacological activity against oxidative stress in ischemia-reperfusion, inflammation and other pathological conditions.

Modified approach for preparing (E)-stilbenes related to resveratrol, and evaluation of their potential immunobiological effects

Resveratrol and closely related stilbenoids belong to the most intensively studied biologically active compounds. This interest evoked several attempts to prepare such compounds in a convenient synthetic way. Our approach allowed obtaining largely methoxystilbenes, formed as E-isomers only (using Wittig–Horner synthesis as the key step), which were further demethylated by boron tribromide. The hydroxymethoxystilbenes (e.g. pterostilbene) were prepared using isopropyl protection, later selectively deprotected by boron trichloride. The method is suitable for preparing such compounds in a large amount. Effects of the obtained stilbene derivatives on immunobiological responses triggered by lipopolysacharide and interferon-γ were tested under in vitro conditions. Namely production of nitric oxide (NO) was investigated, and relation between the molecular structure and immunobiological activity was assessed.

Formation of reactive oxygen and nitrogen species in the presence of pinosylvin - an analogue of resveratrol

OBJECTIVE

Formation of reactive oxygen species in neutrophils of rats with adjuvant arthritis and generation of nitric oxide in RAW 264.7 macrophages were analysed in the presence of pinosylvin.

METHODS AND RESULTS

The method of chemiluminescence was used for the detection of reactive oxygen species in blood of rats with adjuvant arthritis. Pinosylvin (50 mg/kg, daily, p.o.) and methotrexate (0.4 mg/kg, twice a week, p.o.) were applied separately or in a combination over a period of 28 days from the day of immunisation. Adjuvant arthritis was accompanied by a significantly increased number of neutrophils, by elevated concentration of oxidants in blood and by excessive responsiveness of neutrophils to stimulation with PMA. In rats treated with methotrexate, all these changes were significantly reduced and the inhibition became more pronounced when methotrexate was applied in the combination with pinosylvin; the monotherapy with pinosylvin did not induce any detectable changes in the parameters tested. Under in vitro conditions, pinosylvin inhibited formation of nitric oxide (NO) in macrophages, as demonstrated by the decreased concentration of nitrite - the end-product of NO metabolism (assessed by Griess' method), by the reduced expression of inducible NO synthase (detected by Western blot), and by the failure of pinosylvin to scavenge nitric oxide (measured amperometrically in cell-free system).

CONCLUSION

The observed ability of pinosylvin to decrease concentration of reactive oxygen and nitrogen species, along with its capacity to enhance the efficacy of methotrexate in arthritis treatment may shed more light into the pharmacological potential of this prospective natural substance.

Suppression of oxidative burst in human neutrophils with the naturally occurring serotonin derivative isomer from Leuzea carthamoides

OBJECTIVE

Neutrophil leukocytes and macrophages represent professional phagocytic cells. When appropriately stimulated, they undergo dramatic physiological and biochemical changes resulting in phagocytosis, chemotaxis and degranulation with the activation of reactive oxygen species (ROS) production known as the respiratory burst.

DESIGN

In this study we analysed the effect of a crystalline complex fraction of four N-feruloyl-serotonin isomers isolated from the seeds of Leuzea carthamoides on the mechanism of oxidative burst of human neutrophils in vitro.

RESULTS

N-feruloyl-serotonin (N-f-5HT) inhibited dose-dependently oxidative burst of human whole blood and isolated neutrophils in vitro stimulated with phorbol-myristate-acetate (PMA) as measured by luminol/isoluminol enhanced chemiluminescence.In isolated neutrophils stimulated with PMA, N-f-5HT was effective against extracellular as well as intracellular reactive oxygen species. Western blot analysis documented that N-f-5HT in concentrations of 10 and 100 µM significantly decreased PMA-induced phosphorylation of protein kinase C alpha/beta II.

CONCLUSION

The results suggest that N-f-5HT represents an effective naturally occurring substance with potent effect on the oxidative burst of human neutrophils and could be further investigated for its pharmacological activity against oxidative stress in ischaemia-reperfusion, inflammation and other pathological conditions.

In vivo effect of pinosylvin and pterostilbene in the animal model of adjuvant arthritis

OBJECTIVE

The aim of this study was to evaluate the effects of pinosylvin (PIN) and pterostilbene (PTE), natural substances from the stilbenoid group, on the development of adjuvant arthritis in rats.

METHODS

Adjuvant arthritis (AA) was induced by a single intradermal injection of Mycobacterium butyricum in incomplete Freund's adjuvant in male Lewis rats. Our experiments included healthy intact animals as reference controls, arthritic animals without any drug administration, and arthritic animals with administration of PIN and PTE in the oral daily dose of 30 mg/kg b.w. The treatment involved administration of the substances tested from day 0, i.e. the day of immunization, to the experimental day 28. The following parameters were monitored: change of the hind paw volume (HPV) on day 14, 21 and 28, luminol-enhanced chemiluminescence (CL) of the joint and myeloperoxidase (MPO) activity in hind paw joint homogenates (day 28).

RESULTS

Arthritic animals treated with PIN showed a decrease in HPV, significantly on days 14 and 28. PIN decreased CL of the joint as well as MPO activity of the joint homogenate, in comparison with untreated animals. PTE had no effect on HPV and MPO activity in hind paw joint homogenates and exerted only a partial effect on luminol-enhanced CL.

CONCLUSIONS

On the basis of our results we conclude that the effect of PTE on CL was only partial. PIN, on the other hand, had a beneficial anti-inflammatory and antioxidant effect on oxidative stress induced biochemical changes occurring in AA, as determined by all three functional parameters.

Different effect of two synthetic coumarin-stilbene hybrid compounds on phagocyte activity

OBJECTIVE

Activated phagocytes, generating a variety of powerful inflammatory mediators, such as oxygen and nitrogen species, may participate in oxidative stress-mediated inflammation and organ toxicity. At present, great attention is devoted to the important class of phenolic compounds - coumarins - due to their antiinflammatory/antioxidant activities. We compared two synthetic phenylcoumarins: 7-hydroxy-3-(4´-hydroxyphenyl) coumarin (HHC; 0.01-100 µmol/l) and its hydrogenated analogue: 7-hydroxy-3-(4´-hydroxyphenyl)-3,4-dihydrocoumarin (HHDC; 0.01-100 µmol/l) as their ability to inhibit reactive oxygen species (ROS) generation in human neutrophils and nitric oxide (NO) production by RAW 264.7 macrophages in vitro, with respect to some of their physicochemical characteristics.

METHODS

ROS production was measured with luminol-enhanced chemiluminescence (CL) in the microplate luminometer Immunotech LM-01T, nitrite formation was determined by the Griess reaction - spectrophotometrically. The radical scavenging assays were employed to assess the antiradical activity values. The relevant physico-chemical parameters of the compounds tested, electronic and hydrophobic, were determined experimentally as well as by suitable computational programmes.

RESULTS

Both HHC and HHDC were found to decrease significantly (p<0.01) CL of whole blood stimulated with phorbol myristate acetate (PMA) from the concentration of 1 µmol/l. While HHC significantly inhibited CL stimulated by A23187 and opsonized zymosan (OpZ), HHDC was ineffective. Unlike HHDC, HHC in the concentrations of 10 and 100 µmol/l significantly (p<0.01) reduced NO formation in lipopolysaccharide (LPS) -stimulated murine macrophages RAW 264.7. HHC possessed the higher free radical reducing efficacy in accordance with its more favourable values of electronic parameters in comparison with HHDC.

CONCLUSIONS

Our results show the different inhibitory effects of HHC and HHDC on phagocytic activity that might be the result of their diverse free radical scavenging properties and lipophilicity features.

Molecular targets of the natural antioxidant pterostilbene: effect on protein kinase C, caspase-3 and apoptosis in human neutrophils in vitro

OBJECTIVE

Pterostilbene, a naturally occurring phenolic derivative, exhibits various pharmacological effects, e.g. anti-cancerous, antioxidant, anti-inflammatory and anti-diabetic. Based on our previous study, we assessed the cellular and molecular effects of pterostilbene on human neutrophils and in cell free systems. Experimental and theoretical molecular descriptors of stilbene derivatives were also determined.

METHODS

We assessed the antioxidant properties of pterostilbene using cell free system and computational methods. The effect of pterostilbene on protein kinase C activation/phosphorylation was detected by special anti-phospho protein kinase C antibodies. Membrane associated changes determining the life span of neutrophils and human recombinant caspase-3 assay were examined.

RESULTS

Pterostilbene possessed comparable antioxidant properties as resveratrol in cell free system. Computational methods were used to establish the molecular characteristics of stilbene derivatives. The values of electronic parameters suggest a slight enhancement of electron donor properties of pterostilbene compared to resveratrol. Phosphorylation and thus activation of protein kinase C alpha/beta II in activated neutrophils was not decreased by pterostilbene. Pterostilbene in concentrations of 10-100 μM was found to inhibit the activity of human caspase-3 purified enzyme and did not influence cell viability significantly.

CONCLUSION

Pterostilbene, an analog of resveratrol, was identified as a good natural antioxidant compound. However, reducing the oxidative burst of human neutrophils during their activation in vitro with pterostilbene does not include protein kinase C phosphorylation pathway. Pterostilbene showed dose dependent activation/inhibition of caspase-3 enzyme activity.

Affinity chromatography reveals RuBisCO as an ecdysteroid-binding protein

The aim of this work was to isolate plant ecdysteroid-binding proteins using affinity chromatography. Ecdysteroids as insect hormones have been investigated thoroughly but their function and the mechanism of action in plants and other organisms is still unknown although ecdysteroids occur in some plants in a relatively large amount. Therefore, 20-hydroxyecdysone was immobilized on a polymeric carrier as a ligand for affinity chromatography in order to isolate plant ecdysteroid-binding proteins from the cytosolic extract of New Zealand spinach (Tetragonia tetragonoides). Non-specifically bound proteins were eluted with a rising gradient of concentration of sodium chloride, and 3% (v/v) acetic acid was used for the elution of the specifically bound proteins. Using this method, ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) was isolated. The influence of ecdysteroids on RuBisCO was further studied. Our results show that ecdysteroids are able to increase the yield of RuBisCO-mediated reaction in which CO(2) is fixed into organic matter by more than 10%.

Structure-efficiency relationship in derivatives of stilbene. Comparison of resveratrol, pinosylvin and pterostilbene

OBJECTIVES

Oxidative stress is related to a number of autoimmune diseases, e.g. rheumatoid arthritis, cancer, etc. The main source of pathologically working reactive oxygen species (ROS) are activated polymorphonuclear leukocytes (PMNL).

OBJECTIVE

There are some papers comparing structure - pharmacological efficiency relationship of vegetal substances from the stilbenoid group. We compared the effect of trans-resveratrol, which is well-known by its antioxidative activity, with the effect of pinosylvin and pterostilbene.

METHODS

Luminol-enhanced chemiluminescence (CL) was used to study the antioxidative action. The effect was observed in whole blood and in isolated PMNL. The concentrations of substances tested were 0.01-100 microM. Due to the different abilities of luminol and isoluminol to pass through the cell membrane, we studied the effect of the substances tested on intracellular and extracellular ROS. To stimulate the production of ROS we used phorbol-myristate-acetate (PMA), which activates PMNL via protein kinase C.

RESULTS

Resveratrol, pinosylvin and pterostilbene inhibited significantly the CL of whole blood and extra- and intracellular CL of isolated PMNL in a dosedependent manner. Depending on different functional groups of the stilbene molecule, resveratrol inhibited CL of whole blood and isolated PMNL, whereas pinosylvin influenced mainly intracellular CL and pterostilbene extracellular CL.

CONCLUSION

The presence of different functional groups in the molecules of stilbenoids influence their antioxidative effect. Modification of these functional groups may result in derivatives with required antioxidative properties, targeting mainly extracellular ROS which are responsible for tissue damage during chronic inflammation.

Additional minor ecdysteroid components of Leuzea carthamoides

Seventeen additional minor ecdysteroid compounds were isolated and identified from the roots of Leuzea carthamoides (Wild.) DC. Eight of them are new phytoecdysteroids: carthamoleusterone (13) is a new side-chain cyclo-ether with five-membered ring; 14-epi-ponasterone A 22-glucoside (12) is a rare and unusual natural 14 beta-OH epimer; 15-hydroxyponasterone A (11) is also new and rare with its C-15 substituted position, as well as 22-deoxy-28-hydroxymakisterone C (18) possessing secondary hydroxyl in position C-28 and 26-hydroxymakisterone C (20) with hydroxy groups in positions 25 and 26. New are also 1 beta-hydroxymakisterone C (21) and 20,22-acetonides of inokosterone (8) and integristerone A (10). Series of already known ecdysteroids: ecdysone (1), 20-hydroxyecdysone 2- and 3-acetates (3 and 4), turkesterone (6), inokosterone (7), 24-epi-makisterone A (14), and amarasterone A (22) are reported here as new constituents of L. carthamoides. Seven earlier reported Leuzea ecdysteroids: 20-hydroxyecdysone (2), ajugasterone C (5), integristerone A (9), 24(28)-dehydromakisterone A (15), 24(28)-dehydroamarasterone B (16), (24Z)-29-hydroxy-24(28)-dehydromakisterone C (17) and makisterone C (19) are also included because they are now better characterized.

Lack of interference of common phytoecdysteroids with production of nitric oxide by immune-activated mammalian macrophages

Effects of selected common phytoecdysteroids on immunobiological responses triggered by lipopolysaccharide and interferon-gamma (IFN-gamma) were tested under in vitro conditions using murine resident peritoneal macrophages. Namely, production of nitric oxide was investigated. The series of test agents encompassed ecdysteroids occurring often as major components of the ecdysteroid fraction in numerous plant extracts: 20-hydroxyecdysone (20E), polypodine B, ajugasterone C, ponasterone A and inokosterone. Their structural variability concerns only variation in the number and position of hydroxyls. Two additional side-chain modified ecdysteroids: makisterone A (with a methyl substituent at position 24) and carthamosterone (with a cyclic side-chain lactone), and three ecdysteroid analogs: poststerone, rubrosterone and dihydrorubrosterone (devoid of side chains) were included into the test series. All test compounds, except of ponasterone A, represent natural substances isolated from the medicinal plant Leuzea carthamoides and are supposed to be significant for the often reported pharmacological activities of preparations derived from this species. However, the tested ecdysteroids did not interfere with the immunobiological activity of the immunocompetent cells. Our results thus differ from the so far reported information.

Inhibitor of sarco-endoplasmic reticulum Ca2+-ATPase thapsigargin stimulates production of nitric oxide and secretion of interferon-gamma

Thapsigargin is a sesquiterpene lactone of guaianolide type isolated from the Mediterranean plant Thapsia garganica L. It is widely used experimentally as a potent and selective inhibitor of sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) leading to rapid elevation of intracellular calcium [Ca2+]i. Several previous reports have shown that thapsigargin interferes with production of nitric oxide (NO) by mouse peritoneal macrophages and mouse macrophage cell lines. The present data confirm that thapsigargin is a modest inducer of NO in mouse macrophages, production of NO being slightly enhanced by lipopolysaccharide. However, thapsigargin on its own very potently induces NO in macrophages of rats under conditions in vitro. The highest effect was observed after the concentration of 0.25 microM thapsigargin, producing approximately 30 microM accumulation of nitrites in supernatants of cells cultured for 24 h. The aim of our experiments was to investigate immune mechanisms implicated in activation of high-output NO biosynthesis. It has been found that thapsigargin dose-dependently induces secretion of interferon-gamma (IFN-gamma) in macrophages of both rats and mice, and also in human peripheral blood mononuclear cells. The IFN-gamma production was rather low in macrophages of mice while relatively very high levels of IFN-gamma were found in cultures of rat macrophages and human peripheral blood mononuclear cells. The concentration of IFN-gamma produced by 5 microM thapsigargin within the interval of 24 h exceeded 3 ng/ml in rat macrophages and approached 2 ng/ml in cultures of human peripheral blood mononuclear cells. The effects are mediated by mitogen-activated protein kinases (MAPKs) such as p38 mitogen-activated protein kinase (p38) and extracellular signal-regulated kinases 1/2 (ERK1/2), and by nuclear transcriptional factor NF-kappaB. In summary, the original findings demonstrate immunostimulatory potential of thapsigargin and warrant more detailed preclinical studies.

The selective effect of N-feruloylserotonins isolated from Leuzea carthamoides on nociception and anxiety in rats

The effects of N-feruloylserotonins, substances isolated from the seeds of Leuzea carthamoides (WILLD.) DC., on nociception and anxiety were studied in Wistar rats. Nociceptive responses were measured using the plantar and tail-flick tests which were administered before and after swimming stress (3 min, water temperature 32 degrees C). Anxiety was evaluated using an elevated plus maze. In Experiment I, neither basal nociception nor stress-induced analgesia was influenced significantly. Separating the animals into groups based on their basal nociceptive sensitivity, either high- or low-pain threshold revealed that N-feruloylserotonins have selective effects, especially on rats with high-pain thresholds. In these animals, N-feruloylserotonins reduced the stress-induced analgesia that followed swimming stress. In Experiment II, basal nociceptive sensitivity correlated with indicators of anxiety; high-pain threshold rats were more anxious in the elevated plus maze, with less frequent visits to open arms. The opposite effect was seen in low-pain threshold rats. N-feruloylserotonins did not influence anxiety in low-pain threshold rats, although it reduced anxiety in the high-pain threshold rats as indicated by the increased ratio of open arm visit frequency compared to closed arm visit frequency in the elevated plus maze. From these results we concluded that N-feruloylserotonins have selective stress-reducing effects in stress-sensitive animals.

Lignan Glucosides and Serotonin Phenylpropanoids from the Seeds of Leuzea carthamoides

Two lignan glucosides, the known tracheloside and the new carthamoside, together with their two known aglycones, trachelogenin and (7E,8'S)-7,8-didehydroarctigenin (cf. cartha- mogenin), were isolated from the seeds of Leuzea carthamoides. Additional four phenylpropanoid derivatives of tryptamine, the E and Z isomers of N-feruloylserotonin and N-isoferuloylserotonin, were also isolated and identified. Their structure determination and identification were performed by spectroscopic, mainly NMR analysis.

Dimeric Ecdysteroid Analogues and Their Interaction with the Drosophila Ecdysteroid Receptor

Three structurally related specific ecdysteroid derivatives, 7,7'-dimers of 14-deoxy-8(14)-ene transformed 20-hydroxyecdysone, ponasterone A and ajugasterone C, were obtained by photochemical transformation. The structures of the dimeric ecdysteroids were identified mainly by NMR spectroscopy supported by MS and IR spectroscopy. Yields of the dimerisation products were dependent on the reactant concentrations and photoreaction conditions. Inert gas atmosphere supported high yields, whereas oxygen atmosphere fully prevented the dimer formation. All the three dimers retained a rather high agonistic activity at the ecdysteroid receptor in the Drosophila BII bioassay when compared with the relevant original ecdysteroids.

Ecdysteroid Glycosides: Identification, Chromatographic Properties, and Biological Significance

Ecdysteroid glycosides are found in both animals and plants. The chromatographic behavior of these molecules is characteristic, as they appear much more polar than their corresponding free aglycones when analyzed by normal-phase high-performance liquid chromatography (HPLC), whereas the presence of glycosidic moieties has a very limited (if any) impact on polarity when using reversed-phase HPLC. Biological activity is greatly reduced because the presence of this bulky substituent probably impairs the interaction with ecdysteroid receptor(s). 2-Deoxy-20-hydroxyecdysone 22-O-beta-D-glucopyranoside, which has been isolated from the dried aerial parts of Silene nutans (Caryophyllaceae), is used as a model compound to describe the rationale of ecdysteroid glycoside purification and identification.

High-performance liquid chromatographic analysis and separation of N-feruloylserotonin isomers

The N-feruloylserotonin containing fraction was isolated from seeds of Leuzea carthamoides (Willd.) DC by solvent extraction followed by column chromatography on silica gel or on Sephadex LH-20. Nuclear magnetic resonance spectroscopic analysis of the isolated fraction showed the presence of four structurally related compounds. These compounds were identified as four isomers of N-feruloylserotonin: N-(Z)-feruloylserotonin, N-(Z)-isoferuloylserotonin, N-(E)-feruloylserotonin and N-(E)-isoferuloylserotonin. They were analyzed by HPLC on Separon SGX C18, Separon SGX and Separon SGX phenyl, using various mobile phases. Separon SGX phenyl phase was found the most efficient for a rapid analysis and for the final separation of the N-feruloylserotonin isomers.

Biological activities of a specific ecdysteroid dimer and of selected monomeric structural analogues in the B(II) bioassay

The biological activities of selected specific ecdysteroids obtained by photochemical or chemical transformation are compared in the B(II) bioassay, in which the potency reflects the affinity of binding to the ligand-binding site of the Drosophila melanogaster ecdysteroid receptor. The compounds tested represent 14-deoxy, 14-dehydroxy, 14-hydroperoxy and 14-epi derivatives of 20-hydroxyecdysone and were selected on the basis of their close structural relationship to elucidate the contribution of the 14-hydroxy group and the stereochemical configuration at C-14 to ecdysteroid agonist activity. The structure-activity relationship shows that a 14-hydroxy group is not required for activity. However, the alpha-configuration of -H, -OH or -OOH at C-14, which determines the C/D rings trans-annelation, is very significant for activity; it is as important for activity as the well studied A/B rings cis-annelation. Compounds containing a double bond involving C-14 showed low activity with the exception of the specific, and so far unique, ecdysteroid dimer 7,7'-bis-[14-deoxy-8(14)-ene-20-hydroxyecdysone], which was obtained as the main product of the photochemical transformation of 20-hydroxyecdysone. The relatively high biological activity of this dimeric compound is discussed.

Photochemical transformation of 20-hydroxyecdysone: production of monomeric and dimeric ecdysteroid analogues

Structural modification of 20-hydroxyecdysone (20E) based on photochemical transformation yielded dimeric ecdysteroid 7alphaH,7'alphaH-bis-[(20R,22R)-2beta,3beta,20,22,25-pentahydroxy-5beta-cholest-8(14)-en-6-one-7-yl] as a main product. Its structure was determined by detailed NMR analysis. Furthermore, two new monomeric analogues: 14-epi-20-hydroxyecdysone and 14-deoxy-14,18-cyclo-20-hydroxyecdysone were identified in addition to the earlier described 14-deoxy and 14-hydroperoxy derivatives of 20E. Formation of the specific and so far unique ecdysteroid dimer has not been observed in earlier photo-transformation studies. The transformed dimeric analogue of 20-hydroxyecdysone retained the high agonistic activity on the ecdysone receptor in the B(II)-bioassay compared with the original 20E.

Ecdysteroid 7,9(11)-dien-6-ones as potential photoaffinity labels for ecdysteroid binding proteins

Three ecdysteroid 7,9(11)-dien-7-ones (dacryhainansterone, 25-hydroxydacryhainansterone and kaladasterone) were prepared by dehydration of the corresponding 11a-hydroxy ecdysteroids (ajugasterone C, turkesterone and muristerone A, respectively). The biological activities of the dienones in the Drosophila melanogaster B(II) cell bioassay, which reflect the affinity for the ecdysteroid receptor complex, showed that the dienones retain high biological activity. Irradiation at 350 nm of the ecdysteroid dienones (100 nM) with bacterially-expressed dipteran and lepidopteran ecdysteroid receptor proteins (DmEcR/DmUSP or CfEcR/CfUSP), followed by loading with [(3)H]ponasterone A revealed that irradiation of dacryhainansterone or kaladasterone resulted in blocking of >70% of the specific binding sites. Thus, ecdysteroid dienones show considerable potential as photoaffinity analogues for ecdysteroid binding proteins.

Minor Ecdysteroid Components of Leuzea carthamoides

Fourteen minor ecdysteroid components were isolated and identified from the roots of Leuzea carthamoides (Willd.) DC. Two of them are new phytoecdysteroids: leuzeasterone (1) a six-member side-chain lactone, and (24Z)-29-hydroxy-24(28)-dehydromakisterone C (4) a structurally related sitostane type analogue and assumed biogenetic precursor of 1. The next one, 5α-20-hydroxyecdysone (6), is a rare A/B-ring trans-annelated epimer of the most common phytoecdysteroid 20-hydroxyecdysone. Further compounds: makisterone C (3), 3-epi-20-hydroxyecdysone (5), integristerone A (7), integristerone B (8), 22-oxo-20-hydroxyecdysone (10), taxisterone (11), rubrosterone (12), dihydrorubrosterone (13) and poststerone (14), are new constituents of L. carthamoides, though already reported as compounds isolated from other natural sources. Two earlier reported minor Leuzea ecdysteroids: the five-membered side-chain lactone carthamosterone (2) and the 11-hydroxy-substituted analogue isovitexirone (9), are also included because they are now better characterised. Certain previously described Leuzea ecdysteroids were not found in our material, which may indicate geographic, seasonal or cultivar variations.

Chromatographic procedures for the isolation of plant steroids

In this review, we consider the general principles and specific methods for the purification of different classes of phytosteroids which have been isolated from plant sources: brassinosteroids, bufadienolides, cardenolides, cucurbitacins, ecdysteroids, steroidal saponins, steroidal alkaloids, vertebrate-type steroids and withanolides. For each class we give a brief summary of the characteristic structural features, their distribution in the plant world and their biological effects and applications. Most classes are associated with one or a few plant families, e.g., the withanolides with the Solanaceae, but others, e.g., the saponins, are very widespread. Where a compound class has been extensively studied, a large number of analogues are present across a range of species. We discuss the general principles for the isolation of plant steroids. The predominant methods for isolation are solvent extraction/partition followed by column chromatography and thin-layer chromatography/HPLC.

Synergistic insecticidal mode of action between sesquiterpene lactones and a phototoxin, alpha-terthienyl

The synergistic insecticidal action of characteristic defensive substances produced by the plant family Asteraceae was investigated under controlled laboratory conditions. Sesquiterpene lactones isolated from Asteraceae that may form, through a Michael addition process, conjugates with glutathione were administered in a meridic diet to a herbivorous insect, Manduca sexta. By administering sesquiterpenes, variable in vivo reduced glutathione levels were observed in the insect larvae. When the Asteraceae-derived photooxidant alpha-terthienyl was co-administered, lipid peroxidation and larval mortality were significantly enhanced in the treated groups of insects with lowered in vivo glutathione levels.

Biological activity of natural and synthetic ecdysteroids in the BII bioassay

The potencies of 19 ecdysteroids are compared in the BII bioassay, which reflects the affinity of binding to the ligand binding site of the Drosophila melanogaster ecdysteroid receptor. The compounds tested represent either natural products isolated from plants (phytoecdysteroids) or fungi (mycoecdysteroids) or synthetic analogues based on insect metabolites (zooecdysteroids). None of the tested compounds showed any antagonistic activity, but all possessed quantifiable agonistic activity. All the mycoecdysteroids were less potent than the major insect ecdysteroid, 20-hydroxyecdysone (20E). Also, conjugation of 20E with a glucose moiety results, as expected, in considerable reduction in biological activity, but the remaining activity is dependent on the position of conjugation. The implications of these findings for the structure/activity relationship of ecdysteroids are discussed.

Cyclic Phenylboronates of Ecdysteroids as Products of Regiospecific Reaction with Phenylboronic Acid

The diol system in the side-chain of ecdysteroids reacts with phenylboronic acid under formation of cyclic esters. Phenylboronates of ecdysteroids I - V were prepared. The regiospecific reaction course was confirmed by 1H NMR spectra of the products. The reaction conditions were studied for 20-hydroxyecdysone (I). The phenylboronate can be prepared in high yields even in aqueous solutions. The liberation of the ecdysteroid I from the corresponding phenylboronate VI was performed using various reagents - diols or carboxylic acids.

Effects of pyrrolizidine alkaloids and sesquiterpenes on snail feeding

We determined in the laboratory the feeding response of two populations of the generalist herbivorous snail Arianta arbustorum (Helicidae) towards the composite Adenostyles alliariae and towards various allelochemicals. These were: a pyrrolizidine alkaloid (PA) extract of Adenostyles leaves; senecionine (a PA present in Adenostyles); retrorsine (a PA not present in Adenostyles) and two sesquiterpene (ST) fractions from Adenostyles: a mixture of the STs adenostylone and neoadenostylone, and deacyladenostylone. Tertiary PAs and PA N-oxides were tested separately. For each allelochemical, we tested whether it was deterrent or whether it induced changes of feeding behaviour (i.e. whether it had pre- or postingestive effects), and whether the effects were more pronounced with younger (smaller) snails. The tertiary PA extract from Adenostyles was deterrent, especially for young snails, but did not induce changes of feeding behaviour. Tertiary PA senecionine was deterrent for young snails only and induced changes of feeding behaviour. Also, consumption of untreated Petasites was higher after this treatment. Tertiary PA retrorsine was not deterrent, but induced changes of feeding behaviour. The PA N-oxides showed no activity against the snails. The mixture of adenostylone and neoadenostylone was deterrent and induced feeding aversions. Deacyladenostylone was highly deterrent, but did not induce changes of feeding behaviour. At the Jura site, PA content of Adenostyles was lower than at the Black Forest site. The snails from Jura consumed much less Adenostyles than the snails from Black Forest, and also ate a little less of the treated leaf discs. The PAs which are encountered by the snails in their natural food plants (PA extract and senecionine) were more deterrent than retrorsine (a novel compound). This suggests that the snails have mechanisms for the rejection of allelochemicals which they encounter in their natural food plants, but not for novel allelochemicals. The results suggest two hypotheses regarding the function of the allelochemicals in Adenostyles: (1) The allelochemicals act mainly on very young snails. (2) PAs render Adenostyles toxic, while STs act as feeding deterrents.