Brain and cognitive changes in patients with long COVID compared with infection-recovered control subjects

Between 2.5 and 28% of people infected with SARS-CoV-2 suffer Long COVID or persistence of symptoms for months after acute illness. Many symptoms are neurological, but the brain changes underlying the neuropsychological impairments remain unclear. This study aimed to provide a detailed description of the cognitive profile, the pattern of brain alterations in Long COVID and the potential association between them. To address these objectives, 83 patients with persistent neurological symptoms after COVID-19 were recruited, and 22 now healthy controls chosen because they had suffered COVID-19 but did not experience persistent neurological symptoms. Patients and controls were matched for age, sex and educational level. All participants were assessed by clinical interview, comprehensive standardized neuropsychological tests and structural MRI. The mean global cognitive function of patients with Long COVID assessed by ACE III screening test (Overall Cognitive level - OCLz= -0.39± 0.12) was significantly below the infection recovered-controls (OCLz= +0.32± 0.16, p< 0.01). We observed that 48% of patients with Long COVID had episodic memory deficit, with 27% also impaired overall cognitive function, especially attention, working memory, processing speed and verbal fluency. The MRI examination included grey matter morphometry and whole brain structural connectivity analysis. Compared to infection recovered controls, patients had thinner cortex in a specific cluster centred on the left posterior superior temporal gyrus. In addition, lower fractional anisotropy (FA) and higher radial diffusivity (RD) were observed in widespread areas of the patients' cerebral white matter relative to these controls. Correlations between cognitive status and brain abnormalities revealed a relationship between altered connectivity of white matter regions and impairments of episodic memory, overall cognitive function, attention and verbal fluency. This study shows that patients with neurological Long COVID suffer brain changes, especially in several white matter areas, and these are associated with impairments of specific cognitive functions.

Case Report: Exacerbation of Relapses Following mRNA COVID-19 Vaccination in Multiple Sclerosis: A Case Series

Introduction

mRNA coronavirus disease 2019 (COVID-19) vaccination has been widely used to arrest the spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Rarely, autoimmune events such as relapses in patients with multiple sclerosis (MS) have been reported after vaccination. However, the possible effects of vaccination in a patient already experiencing the symptoms of a relapse represent an unusual scenario that has not been described.

Patients and Methods

This is a retrospective case series of four patients from three major tertiary referral centers that received mRNA COVID-19 vaccination after starting with symptoms of acute demyelination of the central nervous system due to non-recognized MS. A detailed description of each case, including MRI studies, serum light-neurofilament levels, and cerebrospinal fluid (CSF) cytokine profile, is provided.

Case Description

All patients presented exacerbation of ongoing symptoms after vaccination (range 14-112 days first dose). All patients presented MRI features suggestive of highly active MS and fulfilled McDonald 2017 criteria at the time of presentation. All patients presented high serum light-neurofilament levels and oligoclonal G bands restricted to the CSF. Higher levels of interleukin-6 in the CSF were present in the more severe cases.

Discussion

We describe exacerbation of relapses after mRNA COVID-19 vaccination. We hypothesize RNA sensors such as Toll-like receptor 7 may be activated and contribute to amplify the inflammatory response during a relapse.

Conclusion

Patients should seek medical attention if experiencing acute neurological symptoms, especially before vaccination. Fast diagnostic procedures and prompt treatment should be performed in these patients. Pharmacovigilance and further study are warranted to confirm causality.

[Importance of the forensic autopsy in the diagnosis of septic shock: a case report]

Septic shock sometimes starts with unspecific symptoms that hamper the clinical diagnosis and, therefore an appropriate treatment. When the septic shock follows a fulminating course with a fatal outcome, the etiological diagnosis has to be conducted post-mortem. Sudden unexpected deaths in children and young adults are frequently the object of medico-legal autopsies. Some sudden unexpected deaths have an infectious origin, which requires further analyses, including microbiology, to establish the cause of death. Here, the case of a fatal septic shock in a 19-month old male infant is presented. After a mild foot injury, an infection by Streptococcus pyogenes progressed to septic shock with a fatal outcome as post-mortem studies demonstrated.

Antipsoriatic effects of avarol-3'-thiosalicylate are mediated by inhibition of TNF-alpha generation and NF-kappaB activation in mouse skin

BACKGROUND AND PURPOSE

Avarol is a marine sesquiterpenoid hydroquinone with anti-inflammatory and antipsoriatic properties. The aim of this study was to evaluate the in vitro and in vivo pharmacological behaviour of the derivative avarol-3'-thiosalicylate (TA) on some inflammatory parameters related to the pathogenesis of psoriasis.

EXPERIMENTAL APPROACH

Human neutrophils and monocytes as well as the human keratinocyte cell line HaCaT were used to study the effect of TA on oxidative stress, the arachidonic acid pathway, tumour necrosis factor-alpha (TNF-alpha) release and nuclear factor-kappaB (NF-kappaB) activation. All these parameters were also determined in vivo using the zymosan induced mouse air pouch model and the 12-O-tetradecanoylphorbol-13-acetate (TPA) induced mouse epidermal hyperplasia model.

KEY RESULTS

TA showed antioxidant properties in human neutrophils and in the hypoxanthine/xanthine oxidase assay. This compound reduced, in a concentration-dependent manner, leukotriene B(4), prostaglandin E(2) and TNF-alpha production in activated leukocytes. Oral and intrapouch administration of TA in the mouse air pouch model produced a dose-dependent reduction of all these inflammatory mediators. TA also inhibited secretory phospholipase A(2) activity and NF-kappaB DNA-binding in HaCaT keratinocytes. In TPA-induced mouse epidermal hyperplasia, topical administration of TA reduced oedema, leukocyte infiltration, eicosanoid levels and TNF-alpha in skin. In addition, interleukin (IL)-1beta and IL-2 production were also inhibited. Finally, TA was also capable of suppressing NF-kappaB nuclear translocation in vivo.

CONCLUSIONS AND IMPLICATIONS

TA inhibited several key biomarkers up-regulated in the inflammatory response of psoriatic skin and this compound could be a promising antipsoriatic agent.

VIP down-regulates TLR4 expression and TLR4-mediated chemokine production in human rheumatoid synovial fibroblasts

OBJECTIVES

Vasoactive intestinal peptide (VIP) has demonstrated therapeutic effects in arthritis by inhibiting both innate and acquired immune responses. We investigated the potential effects of VIP in the regulation of Toll-like receptor (TLR) expression and function in synovial fibroblasts from patients with rheumatoid arthritis (RA) and osteoarthritis (OA).

METHODS

Cultured fibroblast-like synoviocytes (FLS) were obtained from patients with RA and OA. The effects of VIP on basal or TNF-alpha or lipopolysaccharide (LPS)-induced TLR2, TLR4 and MyD88 expression and its effects on TLR4-mediated CCL2 and CXCL8 chemokine production were studied by reverse transcription-polymerase chain reaction, western blotting and enzyme-linked immunosorbent assay.

RESULTS

TLR2, TLR4 and MyD88 mRNA expression was increased in RA FLS compared with OA FLS. The largest increase was observed for TLR4 and there was also overexpression at the protein level in RA FLS. TLR4 and MyD88 mRNA and proteins were induced by LPS and TNF-alpha in RA FLS. VIP down-regulated the induced but not the constitutive expression of TLR4 and MyD88 in RA FLS. VIP treatment decreased CCL2 and CXCL8 chemokine production in response to TLR4 activation with LPS in RA FLS.

CONCLUSIONS

We demonstrate that VIP down-regulates LPS and TNF-alpha activation of TLR4 expression and the TLR4 functional response in terms of proinflammatory chemokine production. These studies suggest that the pleiotropic anti-inflammatory actions of VIP involve inhibitory effects on TLR4 expression and signalling.

Inhibition of acute and chronic inflammatory responses by the hydroxybenzoquinonic derivative rapanone

Rapanone (2,5-dihydroxy-3-tridecyl-1,4-benzoquinone), a natural compound isolated from Myrsine guianensis growing in the Andean highlands of Colombia, was studied in different in vitro and in vivo models as a potential antioxidant and anti-inflammatory drug. Rapanone showed a mild anti-lipoperoxidative profile in rat liver microsomes and inhibited potently degranulation (IC(50) of 9.8 microM) and superoxide chemiluminescence (IC(50) of 3.0 microM) in human neutrophils. In addition, rapanone is a selective and potent human synovial PLA(2) inhibitor (IC(50) of 2.6 microM). In vivo experiments using the carrageenan paw oedema and the zymosan air pouch model in mice as well as the adjuvant arthritis model in rats have proved that rapanone is very efficient in controlling the inflammatory process by different administration routes.

New sesquiterpene derivatives from the sponge Dysidea species with a selective inhibitor profile against human phospholipase A2 and other leukocyte functions

Two new sesquiterpene cyclopentenones, dysidenones A and B (2, 3), and a new sesquiterpene aminoquinone, dysidine (4), all containing the same rearranged drimane skeleton, have been isolated from a Dysidea sp. sponge, along with bolinaquinone (1). The structures were established from 2D NMR data. Bolinaquinone (1), dysidine (4), and a 1:1 mixture of dysidenones A and B (2, 3) significantly inhibited human synovial phospholipase A2 (PLA2) at 10 microM. Compound 4, which shows an IC50 value of 2.0 microM, exerts a higher potency and selectivity toward this enzyme than the reference inhibitor manoalide. In addition, all of these compounds modulated at 10 microM other human leukocyte functions such as the degranulation process measured as elastase release and the superoxide production measured by chemiluminescence.

Dysidotronic acid, a new sesquiterpenoid, inhibits cytokine production and the expression of nitric oxide synthase

In a previous study, we reported a new bioactive sesquiterpenoid, named dysidotronic acid, to be a potent, selective human synovial phospholipase A(2) inhibitor. Dysidotronic acid is a novel, non-complex manoalide analogue lacking the pyranofuranone ring. We now investigate the effect of this compound on cytokine, nitric oxide and prostanoid generation on the mouse macrophage cell line RAW 264.7, where it showed a dose-dependent inhibition with inhibitory concentration 50% values in the micromolar range. This effect was also confirmed in the mouse air pouch injected with zymosan. Dysidotronic acid inhibited the production of tumor necrosis factor alpha and interleukin-1 beta as well as the production of nitric oxide, prostaglandin E(2) and leukotriene B(4). Decreased nitric oxide generation was the consequence of inhibition of the expression of nitric oxide synthase, whereas PGE(2) and LTB(4) reduction was due to inhibition of arachidonic acid bioavailability through a direct inhibitory effect of dysodotronic acid on secretory phospholipase A(2).

Cavernolide: a new inhibitor of human sPLA2 sharing unusual chemical features

The inhibitory effect of cavernolide, a novel C2, terpene lactone isolated from the sponge Fasciospongia cavernosa, on PLA2 and other enzyme activities involved in the inflammatory process was studied. Cavernolide inhibited human synovial sPLA2 in a concentration-dependent manner with an IC50 value of 8.8 microM. Besides, this compound decreased in the nanomolar range the myeloperoxidase degranulation process using different stimuli. Cavernolide also inhibited TNFalpha, NO and PGE2 production in intact cell experiments. NO and PGE2 reduction was the consequence of the inhibition on iNOS and COX-2 expression because it did not affect inducible nitric oxide synthase and cyclooxygenase-2 activities in intact cells.

New pyridinium alkaloids from a marine sponge of the genus Spongia with a human phospholipase A(2) inhibitor profile

Four new bioactive pyridinium alkaloids, named spongidines A-D (5-8), have been isolated from a Vanuatu sponge of the genus Spongia, together with known petrosaspongiolides D (1) and G (2). Compounds 3 and 4 are 21-hydroxy derivatives of petrosaspongiolides K and P. Structure elucidation was accomplished through extensive 2D NMR experiments (COSY, ROESY, HMBC, HMQC) and IR, UV, and FABMS data. All compounds significantly inhibited human synovial phospholipase A(2) (PLA(2)) at 10 microM, with an IC(50) value of 5.8 microM for compound 4, which is the most potent inhibitor, with a higher selectivity toward this enzyme than the reference inhibitor manoalide. Pyridinium alkaloids (5-8) mainly inhibited human synovial PLA(2). Compound 8, which contains a sulfonic acid group, is the most interesting inhibitor.

Synthesis and enzyme inhibitory activities of a series of lipidic diamine and aminoalcohol derivatives on cytosolic and secretory phospholipases A2

We have synthesised some lipidic diamines and aminoalcohols and examined their behaviour as inhibitors of secretory and cytosolic PLA2. Some structure-activity relationships considerations have been deduced. Compound 14 was a potent and selective inhibitor of cPLA2 and compound 4 showed a dual inhibitory profile against both types of PLA2 while no cytotoxicity at 10 microM on human neutrophils or on murine macrophage line was observed for both.

Co-regulation between cyclo-oxygenase-2 and inducible nitric oxide synthase expression in the time-course of murine inflammation

Many in vitro studies have used cell cultures to focus on the relationships between cyclo-oxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) isoforms. We have investigated the time-course of regulation and the role of COX-2 and iNOS in a model of experimental inflammation in mice, the air pouch injected with zymosan. This study demonstrates that there is an early acute phase (4 h) mediated mainly by eicosanoids, with high levels of prostaglandin E2 (PGE2) produced by cyclo-oxygenase-1. In addition, in the later phase (from 12 h) there is a participation of nitric oxide (NO) and PGE2 accompanied by co-induction of both iNOS and COX-2. These enzymes were detected in migrating leukocytes as well as in macrophages lining the air pouch. Administration of NS398 or indomethacin inhibited PGE2 levels and COX activity, but also nitrite levels and iNOS activity, which was accompanied by a reduction in iNOS expression. Aminoguanidine inhibited nitrite levels and iNOS activity in addition to exerting inhibitory effects on the COX pathway. Treatment of animals with dexamethasone reduced nitrite and PGE2 concentrations in air pouch exudates, as well as iNOS and COX-2 expression in migrating cells. Our results indicate that PGE2 and NO may play in vivo mutual modulatory roles in the inflammatory response caused by zymosan injection into the mouse air pouch, a suitable model to study drugs acting on those pathways.

Manoalide

Manoalide is a potent analgesic and antiinflammatory sesterterpene isolated in 1980 from a marine sponge. The antiinflammatory activity of manoalide is due to inhibition of PLA2, through irreversible binding to several lysine residues. The binding is realized by means of the two masked aldehyde functions present in the polar part of manoalide. Of the two aldehyde groups, only that present in the g-hydroxybutenolide ring seems to be essential, since cacospongionolides, naturally occurring analogues lacking the second masked aldehyde group, were also shown to be irreversible PLA2 inhibitors. It appears that the minimum structural requirement for exhibiting manoalide-like PLA2 inhibition would be the presence in the inhibitor of functional groups able to seize the amino groups of PLA2 lysine residues with formation of stable covalent bonds. Many manoalide analogues have been isolated from marine sponges, most of them sharing PLA2 inhibitory properties. Other interesting bioactivities have also been reported for some of these compounds.

Modulation of acute and chronic inflammatory processes by cacospongionolide B, a novel inhibitor of human synovial phospholipase A2

1. Cacospongionolide B is a novel marine metabolite isolated from the sponge Fasciospongia cavernosa. In in vitro studies, this compound inhibited phospholipase A2 (PLA2), showing selectivity for secretory PLA2 (sPLA2) versus cytosolic PLA2 (cPLA2), and its potency on the human synovial enzyme (group II) was similar to that of manoalide. 2. This activity was confirmed in vivo in the 8 h zymosan-injected rat air pouch, on the secretory enzyme accumulating in the pouch exudate. Cacospongionolide B, that is bioavailable when is given orally, reduced the elevated levels of sPLA2 present in paw homogenates of rats with adjuvant arthritis. 3. This marine metabolite showed topical anti-inflammatory activity on the mouse ear oedema induced by 12-O-tetradecanoylphorbol acetate (TPA) and decreased carrageenin paw oedema in mice after oral administration of 5, 10 or 20 mg kg(-1). 4. In the mouse air pouch injected with zymosan, cacospongionolide B administered into the pouch, induced a dose-dependent reduction in the levels of eicosanoids and tumour necrosis factor alpha (TNFalpha) in the exudates 4 h after the stimulus. It also had a weak effect on cell migration. 5. The inflammatory response of adjuvant arthritis was reduced by cacospongionolide B, which did not significantly affect eicosanoid levels in serum, paw or stomach homogenates and did not induce toxic effects. 6 Cacospongionolide B is a new inhibitor of sPLA2 in vitro and in vivo, with anti-inflammatory properties in acute and chronic inflammation. This marine metabolite was active after oral administration and able to modify TNFalpha levels, and may offer an interesting approach in the search for new anti-inflammatory agents.

Synthesis and comparison of the antiinflammatory activity of manoalide and cacospongionolide B analogues

We have synthesized analogues of two naturally occurring antiinflammatory marine compounds, manoalide and cacospongionolide B, containing a pyranofuranone moiety which is considered the pharmacophoric group. The two compounds, and hence their analogues, differ in the presence or absence in the dihydropyran ring of an hemiacetal function which was considered essential to irreversibly inactivate phospholipase A2 (PLA2). The two series of compounds were tested for their inhibitory effects on secretory PLA2 belonging to the groups I, II, and III, and the activities were found to be similar in both series, irrespective of the presence or absence of the additional hemiacetal function. In addition, the PLA2 inhibitory activity increases with the increasing hydrophobic character of the side chain linked to the pyranofuranone moiety. The most active compounds, FCA and FMA, carry a farnesyl residue linked to the pyranofuranone substructure. The most potent PLA2 inhibitor, FMA, was tested in the mouse carrageenan paw edema at the oral dose of 10 mg/kg and showed an activity similar to the reference antiinflammatory drug, indomethacin.

A new cacospongionolide inhibitor of human secretory phospholipase A2 from the Tyrrhenian sponge Fasciospongia cavernosa and absolute configuration of cacospongionolides

A new inhibitor of human secretory phospholipase A2 (PLA2), cacospongionolide E (4a), has been isolated from the Tyrrhenian sponge Fasciospongia cavernosa. The structure was proposed on the basis of spectroscopic data and by chemical transformations. The absolute configuration of cacospongionolides 2a-4a was established using the modified Mosher's method. Cacospongionolide E was the most potent inhibitor toward human synovial PLA2, showing higher potency than the reference compound manoalide and exerting no signs of toxicity on human neutrophils. It showed high activity in the Artemia salina bioassay and moderate toxicity in the fish (Gambusia affinis) lethality assay.

Petrosaspongiolides M-R: new potent and selective phospholipase A2 inhibitors from the New Caledonian marine sponge Petrosaspongia nigra

Five new bioactive sesterterpenes (1-5) have been isolated from the New Caledonian marine sponge Petrosaspongia nigra Bergquist and named petrosaspongiolides M-R. Their chemical structures were determined from 1D and 2D NMR studies and MS data. All compounds inhibited different preparations of phospholipase A2 (PLA2) by irreversibly blocking these enzymes (particularly human synovial and bee venom, see Table 3), with IC50 values in the micromolar range. Interestingly, these compounds displayed a much lower activity (or no activity at all) toward porcine pancreas and Naja naja venom PLA2 enzymes. The most potent compound, 1 (IC50 1.6 and 0.6 microM for human synovial and bee venom PLA2 enzymes, respectively), was slightly more active than manoalide (6) (IC50 3.9 and 7.5 microM) under our experimental conditions. Compound 3 is more selective, inhibiting human synovial PLA2 to a greater extent than bee venom PLA2.

Suppression of leukotriene B4 and tumour necrosis factor alpha release in acute inflammatory responses by novel prenylated hydroquinone derivatives

A series of prenyl hydroquinone derivatives synthesized as structural analogs of marine products were tested for their effects on inflammatory responses in vitro and in vivo. 2-Prenyl-1,4-hydroquinone (H1), 2-diprenyl-1,4-hydroquinone (H2), 2-triprenyl-1,4-hydroquinone (H3) and 2-tetraprenyl-1,4-hydroquinone (H4) scavenged reactive oxygen species and inhibited 5-lipoxygenase (5-LO) activity in human neutrophils. The inhibition of 5-LO activity was demonstrated in vivo in the mouse air pouch injected with zymosan and arachidonic acid-induced ear inflammation. The four compounds suppressed the production of tumour necrosis factor alpha (TNFalpha) in J774 cells stimulated with lipopolysaccharide (LPS) and also in vivo in the mouse air pouch injected with zymosan. In addition, all prenyl-hydroquinones inhibited the release of nitrite and PGE2 in LPS-stimulated J774 cells, without direct effects on cyclo-oxygenase-1 (COX-1), cyclo-oxygenase-2 (COX-2) or inducible nitric oxide synthase (iNOS) activities in several cell-free systems. The reduction in the length of the lateral chain in prenyl-hydroquinones (1-4 isoprene units) with respect to their marine analogs (7-8 isoprene units) has improved the anti-inflammatory activity of this class of compounds. Marine natural products may be a model to design new anti-inflammatory agents.

Anti-inflammatory activity in mice of extracts from Mediterranean marine invertebrates

The effects of dichloromethane and methanol extracts from the marine invertebrates Leptogorgia ceratophyta, Holothuria tubulosa, Coscinasterias tenuispina and Phallusia fumigata on carrageenan-induced paw oedema in mice were investigated. The dichloromethane extract of Coscinasterias tenuispina and the methanol extract of Holothuria tubulosa administered p.o. at 50, 100 and 150 mg/kg, inhibited oedema in a dose-dependent manner 3 h after administration of carrageenan. Both extracts partially decreased elastase activity and PGE2 levels measured in homogenates from inflamed paws, without affecting the levels of this prostanoid present in stomach homogenates. As observed with the selective inhibitor NS398, both extracts can decrease cyclo-oxygenase activity in inflamed tissues but do not modify the constitutive cyclo-oxygenase enzyme. Therefore, these extracts represent new marine resources for the isolation of novel agents active on inflammatory conditions.

Nitric oxide synthase and cyclo-oxygenase pathways in the inflammatory response induced by zymosan in the rat air pouch

1. We have studied the participation of nitric oxide (NO) in an animal model of inflammation, the rat air pouch stimulated with zymosan. 2. Saline or zymosan was injected into 6-day rat air pouches at different time points and measurements were made of cell migration, levels of nitrite/nitrate (NO2/NO3-), prostaglandin E2 (PGE2), leukotriene B4 (L.TB4) and secretory phospholipase A2 (sPLA2) in exudates. Nitric oxide synthase (NOS) activity was determined in high speed supernatants from cells present in pouch exudates. Western blot analysis was also performed on these samples. 3. Zymosan injection induced a time-dependent increase in leukocyte infiltration, NO2/NO3- levels and cellular NOS activity that reached a peak by 8 h. Western blot analysis showed the same time course for induction of NOS protein. Colchicine administration to rats inhibited cellular infiltration and decreased the levels of NO metabolites and cellular NOS activity zymosan-injected air pouch at 8 h. NOS activity was present in polymorphonuclear leukocytes (PMNs) and monocytes, but not in the lymphocytes present in exudates. This enzyme is calcium-independent and needs NADPH for activity. PGE2 levels in exudates showed a time course inverse to that of NOS activity and NO metabolites, with maximum levels of PGE2 observed at 4 h after zymosan injection. 4. Administration of NG-nitro-L-arginine methyl ester (L-NAME) or aminoguanidine to rats significantly reduced cellular NOS activity, NO2/NO3- levels and chemiluminescence, whereas they were without effect on cell migration and degranulation, eicosanoid levels and sPLA2 activity. 5. Treatment of animals with dexamethasone inhibited cellular NOS activity, NO2/NO3- levels, chemiluminescence and the increase in the levels of PGE2 and LTB4, with only a weak effect on elastase release. 6. Administration of the selective cyclo-oxygenase-2 (COX-2) inhibitor NS398 to rats strongly reduced PGE2 levels in exudates without affecting NO metabolites or NOS activity at 4 h after zymosan injection. 7. Our data indicate that NOS is induced in the zymosan-stimulated rat air pouch model of inflammation. This enzyme is expressed in the cells migrating into the air pouch and caused an increased production of NO metabolites in exudates. The results also suggest the presence of an earlier phase in which eicosanoids play the main role, with participation of COX-2 activity, and a later phase mediated by NO. The endogenous release of NO does not modify prostaglandin biosynthesis in this in vivo model.

Morelloflavone, a novel biflavonoid inhibitor of human secretory phospholipase A2 with anti-inflammatory activity

The flavanonylflavone morelloflavone inhibited secretory phospholipase A2 (PLA2) in vitro, with a high potency on the human recombinant synovial and bee venom enzymes (IC50 = 0.9 and 0.6 microM, respectively). The inhibition was apparently irreversible. In contrast, the compound was inactive on cytosolic PLA2 activity from human monocytes. Morelloflavone scavenged reactive oxygen species generated by human neutrophils (IC50 = 2.7 and 1.8 microM for luminol and lucigenin, respectively) but did not modify cellular responses such as degranulation or eicosanoid release. This biflavonoid exerted anti-inflammatory effects in animal models, with a potent inhibition of 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ear inflammation in mice after topical administration. In this test, morelloflavone was found to decrease oedema and myeloperoxidase levels in ear homogenates ID50 = 58.5 and 74.3 micrograms/ear, respectively). In contrast, this biflavonoid failed to modify arachidonic acid-induced ear inflammation or eicosanoid levels in ear homogenates. A significant anti-inflammatory effect was also observed in the mouse paw carrageenan edema after oral administration, with the highest inhibition at 3 hr after induction of inflammation. Morelloflavone is an inhibitor of secretory PLA2 with selectivity for groups II and III enzymes and may be a pharmacological tool. In addition, it shows anti-inflammatory activity apparently not related to the synthesis of eicosanoids, but likely dependent on other mechanisms such as scavenging of reactive oxygen species.

Inhibition of phospholipase A2 activities and some inflammatory responses by the marine product ircinin

The marine product ircinin has been tested for its effects on secretory and cytosolic phospholipase A2 (PLA2) activities in vitro as well as for inhibition of cellular functions in human neutrophils and inflammatory responses in mice. Ircinin inhibited Naja naja venom, human synovial recombinant, bee venom and zymosan-injected rat air pouch PLA2 with IC50 values in the microM range, similar to those of the known inhibitor scalaradial. On the other hand, ircinin was less active on cytosolic PLA2 from human monocytes and decreased potently the release of LTB4 in human neutrophils. This marine product affected weakly human neutrophil functions like superoxide generation and degranulation. In the zymosan-injected rat air pouch ircinin inhibited in vivo the activity of PLA2 present in exudates and reduced dose-dependently myeloperoxidase levels, whereas cell migration was inhibited only at the highest dose tested. This compound exerted a potent anti-oedematous effect after topical application in the mouse ear oedema test. Ircinin is a new inhibitor of PLA2 activity and our results suggest a potential role for this marine product as an inhibitor of inflammatory processes.

Inhibition of inflammatory responses by a series of novel dolabrane derivatives

Four dolabrane derivatives isolated from Endospermum diadenum have been studied for their inhibitory effects on murine models of inflammation and human neutrophil functions in vitro. After topical application, akendo 1, akendo 2 and akendo 3 potently inhibited the mouse ear oedema induced by 12-O-tetradecanoylphorbol acetate (TPA) with a striking effect on myeloperoxidase levels. After oral administration, akendo 2 and akendo 3 inhibited mouse paw oedema induced by carrageenan, with a significant reduction in myeloperoxidase levels. In contrast to indomethacin, they did not modify the prostaglandin E2 content of the inflammed paw. None of the compounds affected superoxide generation by human neutrophils. On the contrary, they inhibited degranulation induced by different stimuli. The most effective compounds were akendo 2 and akendo 3, which also inhibited myeloperoxidase activity. All compounds were weak inhibitors of leukotriene B4 synthesis and release by human neutrophils, whereas only akendo 3 decreased 5-lipoxygenase activity. Cyclo-oxygenase-1 from human platelets was inhibited mainly by akendo 2 and akendo 3, although with a low potency. The latter compound also reduced weakly the synthesis of prostaglandin E2 by cyclo-oxygenase-2. The anti-inflammatory activity of these dolabrane derivatives was not related to arachidonic acid mobilization or metabolism.

Effect of bakuchiol on leukocyte functions and some inflammatory responses in mice

The effects of bakuchiol, a meroterpenoid isolated from the leaves of Psoralea glandulosa L., on phospholipase A2 (PLA2) activity from different sources, human neutrophil responses, zymosan air pouch and topical inflammation in mice, were investigated. This natural product was a weak inhibitor of secretory and intracellular PLA2 but dose-dependently reduced the formation of LTB4 and TXB2 by human neutrophils and platelet microsomes, respectively. In addition, bakuchiol inhibited degranulation in human neutrophils, whereas superoxide generation was not affected. In mice, bakuchiol decreased cell migration, myeloperoxidase activity and eicosanoid levels in the air pouch inflammation induced by zymosan. After topical administration, this compound was effective as an inhibitor of oedema and myeloperoxidase activity in the 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ear oedema and significantly reduced the PGE2 content and ear oedema in the arachidonic acid-induced response. Bakuchiol is a natural anti-inflammatory agent able to control leukocytic functions such as eicosanoid production, migration and degranulation in the inflammatory site.

Pharmacological and biochemical actions of simple coumarins: natural products with therapeutic potential

1. More than 300 coumarins have been identified from natural sources, especially green plants. The pharmacological and biochemical properties and therapeutic applications of simple coumarins depend upon the pattern of substitution. More complex related compounds based on the coumarin nucleus include the dicoumarol/warfarin anticoagulants, aflatoxins and the psoralens (photosensitizing agents). 2. Coumarin itself (1,2-benzopyrone) has long-established efficacy in slow-onset long-term reduction of lymphoedema in man, as confirmed in recent double-blind trials against elephantiasis and postmastectomy swelling of the arm. The mechanism of action is uncertain, but may involve macrophage-induced proteolysis of oedema protein. However, coumarin has low absolute bioavailability in man (< 5%), due to extensive first-pass hepatic conversion to 7-hydroxycoumarin followed by glucuronidation. It may, therefore, be a prodrug. 3. Scoparone (6,7-dimethoxycoumarin) has been purified from the hypolipidaemic Chinese herb Artemisia scoparia and shown to reduce the proliferative responses of human peripheral mononuclear cells, to relax smooth muscle, to reduce total cholesterol and triglycerides and to retard the characteristic pathomorphological changes in hypercholesterolaemic diabetic rabbits. Various properties of scoparone were suggested to account for these findings, including ability to scavenge reactive oxygen species, inhibition of tyrosine kinases and potentiation of prostaglandin generation. 4. Osthole (7-methoxy-8-[3-methylpent-2-enyl]coumarin) from Angelica pubescens, used also in Chinese medicine, causes hypotension in vivo, and inhibits platelet aggregation and smooth muscle contraction in vitro. It may interfere with calcium influx and with cyclic nucleotide phosphodiesterases. 5. Cloricromene, a synthetic coumarin derivative, also possesses antithrombotic antiplatelet actions, inhibits PMN neutrophil function and causes vasodilatation. Some of these properties of cloricromene have been ascribed to inhibition of arachidonate release from membrane phospholipids. 6. Simple coumarins possessing ortho-dihydroxy functions, such as fraxetin and 4-methyldaphnetin, are potent inhibitors (low micromolar) of lipid peroxidation and scavengers of superoxide anion radicals and of aqueous alkylperoxyl radicals, but may be pro-oxidant (enhancing generation of hydroxyl radicals) in the presence of free iron ions. These coumarins also inhibit the proinflammatory 5-lipoxygenase enzyme at micromolar concentrations. Another related coumarin, 5,7-dihydroxy-4-methylcoumarin, is of special interest as it inhibits lipid peroxidation, and scavenges alkylperoxyl and superoxide radicals. Unlike most other simple coumarins studied, 5,7-dihydroxy-4-methylcoumarin also scavenges hypochlorous acid, and is a potent inhibitor of cyclo-oxygenase, but is not pro-oxidant. 7. 5,7- and 6,7-dihydroxy-4-methylcoumarin both reduced the duration of ventricular fibrillation in postischaemic reperfused isolated perfused rat hearts (in which oxygen-derived free radicals are implicated), showing that these antioxidant coumarins possess beneficial properties in this pathophysiological model. 8. In view of the established low toxicity, relative cheapness, presence in the diet and occurrence in various herbal remedies of coumarins, it appears prudent to evaluate their properties and applications further.

Involvement of secretory phospholipase A2 activity in the zymosan rat air pouch model of inflammation

1. In the zymosan rat air pouch model of inflammation we have assessed the time dependence of phospholipase A2 (PLA2) accumulation in the inflammatory exudates as well as cell migration, myeloperoxidase activity, prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) levels. 2. A significant increase in PLA2 activity was detected in 1,200 g supernatants of exudates 8 h after injection of zymosan into rat air pouch. This event coincided with peaks in cell accumulation (mainly neutrophils) and myeloperoxidase activity in exudates and was preceded by a rise in eicosanoid levels. 3. This enzyme (without further purification) behaved as a secretory type II PLA2 with an optimum pH at 7-8 units, lack of selectivity for arachidonate release and dependence on mM calcium concentrations for maximal activity. 4. The PLA2 inhibitors manoalide and scalaradial inhibited this enzyme activity in vitro in a concentration-dependent manner. Scalaradial also inhibited zymosan stimulated myeloperoxidase release in vitro. 5. Injection of the marine PLA2 inhibitor scalaradial together with zymosan into the pouch at doses of 0.5, 1 and 5 mumol per pouch resulted in a dose-dependent inhibition of PLA2 activity in exudates collected 8 h later. Myeloperoxidase levels and cell migration were also decreased, while eicosanoid levels were not modified. 6. Colchicine administration to rats prevented infiltration and decreased PLA2 levels in the 8 h zymosan-injected air pouch. 7. These results indicate that during inflammatory response to zymosan in the rat air pouch a secretory PLA2 activity is released into the exudates. The source of this activity is mainly the neutrophil which migrates into the pouch. 8. Scalaradial exerts anti-inflammatory effects in the zymosan air pouch.

Effects of marine 2-polyprenyl-1,4-hydroquinones on phospholipase A2 activity and some inflammatory responses

Three 2-polyprenyl-1,4-hydroquinone derivatives (2-heptaprenyl-1,4-hydroquinone: IS1, 2-octaprenyl-1,4-hydroquinone: IS2 and 2-[24-hydroxy]-octaprenyl-1,4-hydroquinone: IS3) isolated from the Mediterranean sponge Ircinia spinosula, were evaluated for effects on phospholipase A2 activity of different origin (Naja naja venom, human recombinant synovial fluid and bee venom), as well as on human neutrophil function and mouse ear oedema induced by 12-O-tetradecanoylphorbol 13-acetate (TPA). IS1 interacted minimally with these responses. In contrast, IS2 and IS3 inhibited human recombinant synovial phospholipase A2 in a concentration-dependent manner, with minor effects on the rest of the enzymes. Both compounds slightly affected superoxide generation and degranulation in human neutrophils, whereas they decreased thromboxane B2 and leukotriene B4 synthesis and release in a mixed suspension of human platelets and neutrophils stimulated by ionophore A23187, with IC50 values in the microM range. IS3 was the most effective inhibitor of the synthesis of thromboxane B2 by human platelet microsomes and of leukotriene B4 by high speed supernatants from human neutrophils. IS2 and IS3 showed topical anti-inflammatory activity against the TPA-induced ear inflammation in mice, with similar effects on oedema and a higher inhibition of IS3 on leukocyte migration, estimated as myeloperoxidase activity in supernatants of ear homogenates. Some structure-activity relationships were established since differences in the prenylated chain attached to the hydroquinone moiety result in important modifications of these inflammatory responses.

Antinociceptive activity of filenadol on inflammatory pain

The novel analgesic filenadol (d, 1-erythro-1-(3',4'-methylenedioxyphenyl)-1- morpholinopropan-2-ol) inhibited phenyl-p-benzoquinone-induced writhing in mice with ID50 values of 68.8 (p.o.), 1.67 (i.v.) and 0.48 (i.c.v.) mg/kg. Hyperalgesia induced by arachidonic acid, PGE2 or LTB4 in this test was also decreased by filenadol (ID50 = 24.4, 3.7 and 50.1 mg/kg p.o., respectively). This compound was effective on PGE2, LTB4, bradykinin, PAF or IL-1 beta-induced decrease in pain threshold in the rat paw pressure model and almost totally suppressed the writhing induced by zymosan in mice, while peritoneal production of 6-ketoPGF1 alpha was inhibited by 48.5-62% and only at 100 mg/kg significant inhibition of LTC4 was achieved. The late phase of formalin-induced pain response in mice was prevented by filenadol, without affecting the oedema. Filenadol is an antinociceptive agent that reduces the hyperalgesic effects of inflammatory mediators besides inhibiting partially the synthesis of eicosanoids.

Synthesis and pharmacological evaluation of 2'-hydroxychalcones and flavones as inhibitors of inflammatory mediators generation

2'-Hydroxy-3,4-dimethoxy-3',4'-dimethylchalcone (3a), 2'-hydroxy-3',4',3,4-tetramethoxychalcone (3b), and their corresponding flavones, 3',4'-dimethoxy-7,8-dimethylflavone (4a) and 3',4',7,8-tetramethoxyflavone (4b), were prepared from 3,4-dimethoxycinnamic acid and the respective phenol. The four compounds inhibited enzymic lipid peroxidation and showed weak peroxyl scavenging activity. They also reduced LTB4 release from human neutrophils stimulated by A23187. The chalcone 3b was the only compound able to inhibit in a concentration-dependent way, synovial human recombinant phospholipase A2 activity, human platelet TXB2 generation, and human neutrophil degranulation. This chalcone exerted topical antiinflammatory effects in mice.

Antioxidant profile of mono- and dihydroxylated flavone derivatives in free radical generating systems

A number of free radical generating systems were used to investigate the antioxidant properties and structure-activity relationships of a series of monohydroxylated and dihydroxylated flavones. Ortho-dihydroxylated flavones showed the highest inhibitory activity on enzymic and non-enzymic microsomal lipid peroxidation as well as on peroxyl radical scavenging. Most flavones were weak scavengers of hydroxyl radical, while ortho-dihydroxylated flavones interacted with superoxide anion generated by an enzymic system or by human neutrophils. This series of compounds did not exert cytotoxic effects on these cells. Scavenging of superoxide and peroxyl radicals may determine the antioxidant properties of these active flavones.

Inhibition of inflammatory responses by epitaondiol and other marine natural products

The marine metabolites pacifenol, stypotriol triacetate and epitaondiol were tested for their effects on a number of inflammatory responses. Epitaondiol exhibited a potent topical anti-inflammatory activity related to inhibition of leukocyte accumulation. The other compounds showed a lower potency, similar to that of indomethacin. None of the compounds affected superoxide generation by human neutrophils but pacifenol effectively inhibited the degranulation response. This compound and epitaondiol decreased the release of eicosanoids with a higher potency on the cyclo-oxygenase pathway. Only epitaondiol inhibited human recombinant synovial phospholipase A2 activity in a concentration-dependent manner.

A study of the novel anti-inflammatory agent florifenine topical anti-inflammatory activity and influence on arachidonic acid metabolism and neutrophil functions

We have evaluated the effects of the novel anti-inflammatory agent florifenine, 2-(1-Pyrrolidinyl)ethyl N-[7-(trifluoromethyl)-4-quinolyl]anthranilate, on topical inflammation in mice, free radical-mediated reactions, arachidonic acid metabolism and some neutrophil functions. Topical administration of florifenine produced dose-related anti-inflammatory activity in 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ear oedema and with a lower potency, in the response induced by arachidonic acid (AA). Florifenine also inhibited neutrophil migration and PGE2 content in the inflammed ears. In human whole blood, florifenine was a potent and selective inhibitor of TXB2 generation. This anti-inflammatory agent did not exert antioxidant effects but inhibited elastase release in human neutrophils without affecting superoxide anion generation. Florifenine administration to mice dose-dependently inhibited leukocyte migration and PGE2 levels in the air pouch inflammation induced by zymosan. These results demonstrate the topical anti-inflammatory activity of florifenine and provide a basis for understanding the mechanisms involved in the inhibitory effects of this agent on inflammatory responses.

Inhibitory activity of a series of coumarins on leukocyte eicosanoid generation

Sixteen plant-derived or synthetic coumarins with different patterns of substitution were tested for their capacity to modify A23187-induced synthesis of leukotriene B4 and thromboxane B2 via the 5-lipoxygenase and cyclooxygenase pathways of arachidonate metabolism in rat peritoneal exudate leukocytes. Five of the 16 coumarins inhibited LTB4 production: all contain orthodihydroxy substitutions (approximate IC50 values 8-100 microM). The mechanism is likely to depend upon a combination of the coumarins' iron-chelating and iron ion-reducing abilities, properties which also confer beneficial activities of these compounds as scavengers of reactive oxygen species (Payá et al., Biochem. Pharmacol. 44, 205-214 (1992)). Inhibition of the cyclooxygenase pathway was only demonstrated by one compound, 5,7-dihydroxy-4-methylcoumarin, which did not inhibit 5-lipoxygenase, indicating that the cyclooxygenase inhibitory mechanism is different. Similar effects of the active coumarins were obtained using arachidonic acid as substrate for rat leukocyte eicosanoid generation, confirming that they act at the 5-lipoxygenase/cyclooxygenase level. The same profile of activity was also shown when the coumarins were tested against 5-lipoxygenase in human polymorphonuclear neutrophils. Taken together, these antioxidant and anti-eicosanoid properties of coumarins could be exploited for the design of potentially valuable non-toxic anti-inflammatory agents for treating diseases in which eicosanoid generation and the production of reactive oxygen species are involved.

Avarol and avarone, two new anti-inflammatory agents of marine origin

The anti-inflammatory activity of avarol and avarone, sesquiterpenoid derivatives from the Mediterranean sponge Dysidea avara, was investigated. Both compounds potently inhibited paw oedema induced by carrageenan (approximated ED50 = 9.2 and 4.6 mg/kg, p.o., respectively) as well as ear oedema induced by 12-O-tetradecanoylphorbol acetate (TPA; ED50 = 97 and 397 micrograms/ear, respectively) in mice, with effects comparable to those of indomethacin. In A23187-stimulated rat peritoneal leukocytes, avarol showed an IC50 = 0.6 and 1.4 microM for inhibition of leukotriene B4 and thromboxane B2 release, respectively, with avarone showing a slightly lower potency. Both marine metabolites failed to show xanthine oxidase inhibitory activity or superoxide scavenging effects but were potent inhibitors of superoxide generation in rat peritoneal leukocytes activated by different stimuli, with an IC50 below the microM range. Only avarol was able to inhibit human recombinant synovial phospholipase A2 activity with an IC50 = 158 microM, and thus this compound showed a potency higher than that of mepacrine. Avarol and avarone effectively control acute inflammation in experimental models after either oral or topical administration and their anti-inflammatory activity may result from inhibition of eicosanoid release and depression of superoxide generation in leukocytes.

Hispidulin protection against hepatotoxicity induced by bromobenzene in mice

The effects of the natural flavonoid hispidulin (6-methoxy-5,7,4'-trihydroxyflavone) on bromobenzene-induced hepatotoxicity in mice were investigated. We found a correlation between liver injury and hepatic lipid peroxidation besides a strong liver glutathione depletion due to the toxicant. Hispidulin at doses between 50 and 150 mg/kg i.p. compared favourably with the reference compound N-acetyl-L-cysteine for inhibition of liver injury and lipid peroxidation. The flavonoid at the highest dose tested was also able to counteract reduced glutathione depletion induced by bromobenzene in starved mice. These hepatoprotective effects can be related to the antioxidant properties of hispidulin.

Effects of flavonoids on Naja naja and human recombinant synovial phospholipases A2 and inflammatory responses in mice

Six flavonoid derivatives were tested for their influence on Naja naja and human recombinant synovial phospholipase A2. They showed a selectivity for the last enzyme with IC50 = 14.3, 17.6, 12.2 and 28.2 microM for quercetagetin, kaempferol-3-O-galactoside, scutellarein and scutellarein-7-O-glucuronide, respectively, while reduced effects were observed for hispidulin and hibifolin. After topical application all the flavonoids inhibited 12-O-tetradecanoylphorbol-13-acetate-induced ear oedema in mice with a potency comparable to that of indomethacin and they were also able to inhibit carrageenan-induced mouse paw oedema at a dose of 150 mg/kg p.o. The blockade of the free hydroxyl at C-7 or C-6 reduced the anti-inflammatory activity and also the inhibitory effect on human recombinant synovial phospholipase A2. These results are in accordance with the notion that group II phospholipases A2 may play a role in experimental inflammation, although several mechanisms seems to be involved in the anti-inflammatory effect of this group of flavonoids.

Iron-reducing and free-radical-scavenging properties of apomorphine and some related benzylisoquinolines

The scavenging and iron-reducing properties of a series of benzylisoquinolines of natural and synthetic origin have been studied. Bulbocapnine, boldine, glaucine, and stepholidine acted as scavengers of hydroxyl radical in the deoxyribose degradation by Fe(3+)-EDTA + H2O2. On the contrary, laudanosoline, apomorphine, protopapaverine, anonaine, and tetrahydroberberine increased deoxyribose degradation by a mechanism related to generation of superoxide anion. Only apomorphine had a stimulating effect in the system using citrate instead of ethylenediaminetetraacetic acid (EDTA) as well as in the absence of chelator. Apomorphine also stimulated DNA damage by Cu2+. The iron-ion reducing ability of apomorphine and laudanosoline was confirmed using cytochrome c. Both compounds scavenged peroxyl radicals in an aqueous medium, while in Fe(3+)-induced microsomal lipid peroxidation apomorphine acted as an inhibitor and laudanosoline stimulated the process. It is suggested that in microsomes the chain-breaking antioxidant properties of apomorphine overcome its possible influence on redox cycling of iron, or prooxidant properties.

Effects of coumarin derivatives on superoxide anion generation

A number of simple coumarins with different patterns of substitution were tested on activated polymorphonuclear leukocyte superoxide generation and superoxide scavenging using the reduction of nitroblue tetrazolium. The most effective compound was fraxetin, which showed a better potency as an inhibitor of superoxide radical generation than as a scavenger. From the structure-activity study it can be deduced the importance of an ortho-dihydroxyl function, especially at the position 7, 8. Blockade of active hydroxyl groups by methylation or glycosylation decreases the activity. None of the coumarins were cytotoxic on leukocytes as assessed by lactic dehydrogenase activity release. Inhibition of superoxide generation in activated neutrophils may play a role in the vasoprotective effects of simple coumarins.

Effects of phenolic compounds on bromobenzene-mediated hepatotoxicity in mice

1. The hepatic protective effects of the phenolic compounds 7,8-dihydroxyflavone, morin, silymarin, caffeic acid and chlorogenic acid on bromobenzene-induced toxicity in mice were studied. 2. Morin, caffeic acid and chlorogenic acid at an oral dose of 200 mg/kg failed to influence hepatotoxicity in vivo, while 7,8-dihydroxyflavone exhibited efficacy and potency higher than those of the reference compound silymarin. 3. 7,8-Dihydroxyflavone, an antioxidant and hepatoprotective agent in vitro, decreased serum glutamate-pyruvate transaminase levels (SGPT) in a dose-related manner, and at 200 mg/kg inhibited bromobenzene-induced glutathione depletion in liver.

Antioxidant action of benzylisoquinoline alkaloids

The antioxidant action of a series of benzylisoquinoline alkaloids has been investigated. Laudanosoline, protopapaverine, anonaine, apomorphine, glaucine, boldine, bulbocapnine, tetrahydroberberine and stepholidine produced a dose-dependent inhibition of microsomal lipid peroxidation induced by Fe2+/ascorbate, CCl4/NADPH or by Fe3+ ADP/NADPH. Apomorphine exerted the highest inhibitory effects in the three systems of induction used, with a potency higher than propyl gallate. Laudanosoline was particularly effective in the first system, while bulbocapnine and anonaine were more potent when CCl4/NADPH or Fe3(+)-ADP/NADPH were used as inducers. Laudanosoline, protopapaverine, apomorphine, tetrahydroberberine and stepholidine were also potent inhibitors of nitroblue tetrazolium (NBT) reduction. The presence of a free hydroxyl group or preferably of a catechol group is a feature relevant for inhibition of lipid peroxidation and NBT reduction, nevertheless the antioxidant activity of benzylisoquinoline alkaloids cannot be only ascribed to the formation of phenoxy radicals and other free radical species may be formed during aporphine and tetrahydroprotoberberine oxidation. The influence of this series of compounds on the time course of lipid peroxidation suggests that some of them, like apomorphine and boldine act as chain-breaking antioxidants.

Interactions of a series of coumarins with reactive oxygen species. Scavenging of superoxide, hypochlorous acid and hydroxyl radicals

Sixteen plant-derived or synthetic coumarins with various hydroxyl and other substitutions were tested for their ability to inhibit lipid peroxidation and to scavenge hydroxyl radicals, superoxide radicals and hypochlorous acid. Seven unsubstituted or monosubstituted coumarins were essentially inactive in all tests except for ability to scavenge OH with rate constants approximately greater than 1 x 10(9) M-1. sec-1. Of the remaining nine, six containing dihydroxy substitutions were effective inhibitors of Fe3+-ascorbate-dependent microsomal lipid peroxidation (IC50 less than 20 microM), with ortho-dihydroxy + one additional substitution optimal (IC50 less than 10 microM). ortho-Dihydroxylated coumarins were pro-oxidant (enhanced OH generation) in the Fe3+-EDTA-H2O2 deoxyribose system but decreased OH' generation in the Fe3+-ascorbate-H2O2 deoxyribose system, indicating that these compounds can both chelate iron ions and also readily donate electrons for redox cycling of Fe3+. The meta-dihydroxycoumarin did not show this behaviour, but was an effective scavenger of hypochlorous acid, a property shared by only one other compound. Several other coumarins with one or more hydroxyl substituents were also capable of effectively removing superoxide anions (IC50 3.7-72 microM), although some could not be quantified due to direct rapid reduction of cytochrome c. We conclude that several compounds, notably 5,7-dihydroxy-4-methylcoumarin, possess beneficial biochemical profiles of interest in relation to pathophysiological processes dependent upon reactive oxygen species.

Inhibition of nonenzymic lipid peroxidation by benzylisoquinoline alkaloids

A group of benzylisoquinoline alkaloids, including five simple benzylisoquinolines, three phtalideisoquinolines, six aporphines, three protoberberines, and two benzophenanthridines, have been studied as inhibitors of lipid peroxidation stimulated by Fe2+/cysteine in rat liver microsomal fractions. Protopapaverine, apomorphine, laudanosoline, tetrahydroberberine, isoboldine, bulbocapnine, boldine, anonaine, glaucine, and stepholidine showed antiperoxidative effects, and structure-activity relationships were established. In simple benzylisoquinolines, the presence of phenolic hydroxyls or similar reactive groups is necessary for inhibition of peroxidation, while in aporphines and protoberberines nonhydroxylated compounds can exert antiperoxidative effects. The phtalideisoquinolines and benzophenanthridines tested were inactive.

Peroxyl radical scavenging by a series of coumarins

Sixteen plant-derived or synthetic coumarins with various hydroxyl and other substitutions were tested for their ability to scavenge alkylperoxyl radicals generated in the aqueous phase by the controlled thermolysis of 2,2'-azo-bis-(2-amidinopropane) dihydrochloride (ABAP). Protection by coumarins against inactivation of lysozyme by the radicals was assayed by measuring the loss of turbidity of suspensions of M. lysodeikticus. Ten of the coumarins were potent scavengers of aqueous peroxyl radicals with activities comparable to n-propyl gallate, desferrioxamine, ferrioxamine and trolox c, yielding IC50 values in the range 21 to 92 micromolar. The presence of 6,7-ortho-dihydroxy functions gave compounds of the greatest potency. Scavenging activity was unrelated to ability to chelate iron ions. The active coumarins are attractive candidates for evaluation as protective agents against disorders in which oxidative stress is implicated.

Structure-activity relationships of polymethoxyflavones and other flavonoids as inhibitors of non-enzymic lipid peroxidation

Polymethoxylated flavones and C-glycosyl derivatives isolated from medicinal plants besides other flavonoid compounds were studied for their influence on lipid peroxidation induced by FeSO4+ cysteine in rat liver microsomes. A number of hydroxyflavones (e.g. luteolin); C-glycosyl-flavones (e.g. orientin); methoxyflavones (e.g. gardenin D) and flavonols (e.g. datiscetin), as well as the flavanol leucocyanidol and the biflavone amentoflavone behaved as inhibitors of non-enzymic lipid peroxidation. Structure-activity relationships were established and it was observed that the structural features for active polyhydroxylated compounds were different from those of polymethoxylated flavones, antiperoxidative flavonoids possessing a high lipophilicity.