Structure-activity relationships for inhibition of prostaglandin cyclooxygenase by phenolic compounds

Pleiotropic Effects of Eugenol: The Good, the Bad, and the Unknown

Phytocompounds and medicinal herbs were used in traditional ancient medicine and are nowadays increasingly screened in both experimental and clinical settings due to their beneficial effects in several major pathologies. Similar to the drug industry, phytotherapy is interested in using nanobased delivery systems to view the identification and characterization of the cellular and molecular therapeutic targets of plant components. Eugenol, the major phenolic constituent of clove essential oil, is a particularly versatile phytochemical with a vast range of therapeutic properties, among which the anti-inflammatory, antioxidant, and anticarcinogenic effects have been systematically addressed. In the past decade, with the emerging understanding of the role of mitochondria as critical organelles in the pathophysiology of noncommunicable diseases, research regarding the role of phytochemicals as modulators of bioenergetics and metabolism is on a rise. Here, we present a brief overview of the major pharmacological properties of eugenol, with special emphasis on its applications in dental medicine, and provide preliminary data regarding its effects, alone, and included in polyurethane nanostructures, on mitochondrial bioenergetics, and glycolysis in human HaCaT keratinocytes.

Synthesis of Hydroxybenzofuranyl-pyrazolyl and Hydroxyphenyl-pyrazolyl Chalcones and Their Corresponding Pyrazoline Derivatives as COX Inhibitors, Anti-inflammatory and Gastroprotective Agents

Five new series of hydroxybenzofuranyl-pyrazolyl chalcones 3a,b, hydroxyphenyl-pyrazolyl chalcones 6a-c and their corresponding pyrazolylpyrazolines 4a, d, 7a-c and 8a-f have been synthesized and evaluated for their in vitro cyclooxygenase (COX)-1 and COX-2 inhibitory activity. All the synthesized compounds exhibited dual COX-1 and COX-2 inhibitory activity with obvious selectivity against COX-2. The pyrazolylpyrazolines 4a-d and 8a-f bearing two vicinal aryl moieties in the pyrazoline nucleus showed more selectivity towards COX-2. Within these two series, derivatives 4c, d and 8d-f bearing the benzenesulfonamide group were the most selective. Compounds 4a-d and 8a-f were further subjected to in vivo anti-inflammatory screening, ulcerogenic liability and showed good anti-inflammatory activity with no ulcerogenic effect. In addition compounds 4c and 8d as examples showed prostaglandin (PG)E2 inhibition % 44.23 and 51.4 respectively, tumor necrosis factor α (TNFα) inhibition % 33.48 and 41.41 respectively and gastroprotective effect in ethanol induced rodent gastric ulcer model. In addition, to explore the binding mode and selectivity of our compounds, 8d and celecoxib were docked into the active site of COX-1 and COX-2. It was found that compound 8d exhibited a binding pattern and interactions similar to that of celecoxib with COX-2 active site, while bitter manner of interaction than celecoxib to COX-1 active site.

α-Dihydroxychalcone-glycoside (α-DHC) isolated from the heartwood of Pterocarpus marsupium inhibits LPS induced MAPK activation and up regulates HO-1 expression in murine RAW 264.7 macrophage

Three phenolic glycosides isolated from the heartwood of Pterocarpus marsupium showed significant free radical and superoxide ion scavenging activity and antioxidant potential that were comparable to, or several folds higher than those of standard antioxidants, trolox and ascorbic acid. The effective concentrations of these compounds were far below their cytotoxic levels. Compound 3, which was characterized to be α-dihydroxychalcone-glycoside (α-DHC), was the most potent one. Subsequent studies demonstrated that α-DHC effectively reduced nitric oxide and cytokine production by the LPS stimulated RAW 264.7 mouse macrophage cell line. The compound effectively attenuated the expression of inflammation-mediating enzymes COX-2 and iNOS at the mRNA as well as protein levels in a concentration dependent manner. It prevented phosphorylation of all the three MAPKs (JNK, ERK, p38) and eventually blocked the activation of downstream elements contributing to inflammation. Phosphorylation of IκB-α and subsequent translocation of NF-κB into the nucleus were restricted, while the expression of stress responsive gene HO-1 was up-regulated. α-DHC targeted Keap-1 by modifying its cysteine thiols, dissociating it from Nrf-2 and facilitating nuclear entry of the latter; and this in turn induced HO-1 expression. Thus α-DHC exerts its anti-inflammatory activity in a dual manner: by down regulating MAPKs and restricting nuclear stabilization of NF-κB at one end, and by disrupting Nrf-2-Keap-1 complex on the other. In conclusion, the anti-inflammatory potential together with its high therapeutic index envisages α-DHC as a prospective candidate molecule for the development of therapeutic strategy against inflammatory disorders.

The effect of a dentifrice containing Magnolia extract on established plaque and gingivitis in man: a six-month clinical study

AIM

The aim was to evaluate the clinical effect of a dentifrice containing 0.3% Magnolia extract on dental plaque and gingivitis.

MATERIAL AND METHODS

The trial was a 6-month double-blind, stratified, randomized and 2-armed parallel group study. Forty-six subjects in the test group brushed their teeth with a dentifrice containing 0.3% Magnolia extract and 48 subjects in the control group brushed with a placebo dentifrice. Plaque and gingivitis were assessed at baseline, 3 and 6 months.

RESULTS

There was a significantly larger gingivitis reduction in the Magnolia group than in the control group (0.26 ± 0.11 versus 0.11 ± 0.12) (P < 0.001). There was a greater increase in the total number of healthy gingival units Gingival Index (GI score 0) in the Magnolia group than in the control group (149% versus 31%) and a larger reduction in inflamed gingival units (GI score 2/3) (60% versus 30%). Furthermore, at sites with similar amounts of plaque, less clinical signs of gingival inflammation were observed in the Magnolia group than in the control group.

CONCLUSION

Six months' unsupervised use of a dentifrice containing 0.3% Magnolia extract resulted in significantly greater gingivitis reduction than a corresponding control dentifrice.

Antinociceptive effects of eugenol evaluated in a monoiodoacetate-induced osteoarthritis rat model

The aim of the present study was to evaluate whether eugenol, the main constituent of clove oil, has the capacity to provide analgesia in the monoiodoacetate-induced rat model of osteoarthritis. Animals (n = 6/group) received either eugenol (20 or 40 mg/kg) or a vehicle by gavage. Daily administrations were initiated 2 days post osteoarthritis induction and continued for the duration of the study (4 weeks). Gait analysis was performed using the CatWalk method and secondary mechanical allodynia was assessed with von Frey filaments. Selected spinal cord peptides (substance P, calcitonin gene-related peptide and dynorphin) were quantified by mass spectrometry. Significant changes were identified in dynamic gait parameters (swing speed, swing phase duration and duty cycle) of the affected limb following 40 mg/kg eugenol treatment compared with the vehicle (p < 0.05). Von Frey results revealed significant differences between the 40 mg/kg treatment and the vehicle group during the first and the third week of the study (p < 0.02). Spinal pain-related peptide analysis revealed a decreased content of substance P and CGRP accompanied by an increase of dynorphin in animals treated with 40 mg/kg eugenol. These results suggest a therapeutic potential of eugenol to alleviate osteoarthritis-related pain.

Efficacy of essential oil mouthwash with and without alcohol: a 3-day plaque accumulation model

Background

The aim of this study was to evaluate the antiplaque effect of a new alcohol free essential oil mouthwash with respect to a control of an essential oil with alcohol mouthwash, using an in vivo plaque regrowth model of 3-days.

Methods

The study was designed as a double-masked, randomized, crossover clinical trial, involving 30 volunteers to compare two different essential oil containing mouthwashes, during a 3-day plaque accumulation model. After receiving a thorough professional prophylaxis at the baseline, over the next 3-days each volunteer refrained from all oral hygiene measures and had two daily rinses with 20 ml of the test mouthwash (alcohol free essential oil) or the control mouthwash (essential oil with alcohol). At the end of the each experimental period, plaque was assessed and the panelists filled out a questionnaire. Each subject underwent a 14 days washout period and there was a second allocation.

Results

The essential oil mouthwash with ethanol shows a better inhibitory effect of plaque regrowth in 3-days than the mouthwash test with only essential oil in the whole mouth (plaque index = 2.18 against 2.46, respectively, p < 0.05); for the lower jaw (plaque index = 2.28 against 2.57, respectively, p < 0.05); for the upper jaw (plaque index = 2.08 against 2.35, respectively, p < 0.05); for the incisors (plaque index = 1.93 against 2.27, respectively, p < 0.05); and the canines (plaque index = 1.99 against 2.47, respectively, p < 0.05).

Conclusion

The essential oil containing mouthwash without alcohol seems to have a less inhibiting effect on the plaque regrowth than the traditional alcoholic solution.

Trial Registration

ClinicalTrials.gov NCT01411618

Predicting cyclooxygenase inhibition by three-dimensional pharmacophoric profiling. Part II: Identification of enzyme inhibitors from Prasaplai, a Thai traditional medicine

Prasaplai is a medicinal plant mixture that is used in Thailand to treat primary dysmenorrhea, which is characterized by painful uterine contractility caused by a significant increase of prostaglandin release. Cyclooxygenase (COX) represents a key enzyme in the formation of prostaglandins. Former studies revealed that extracts of Prasaplai inhibit COX-1 and COX-2. In this study, a comprehensive literature survey for known constituents of Prasaplai was performed. A multiconformational 3D database was created comprising 683 molecules. Virtual parallel screening using six validated pharmacophore models for COX inhibitors was performed resulting in a hit list of 166 compounds. 46 Prasaplai components with already determined COX activity were used for the external validation of this set of COX pharmacophore models. 57% of these components were classified correctly by the pharmacophore models. These findings confirm that the virtual approach provides a helpful tool (i) to unravel which molecular compounds might be responsible for the COX-inhibitory activity of Prasaplai and (ii) for the fast identification of novel COX inhibitors.

Essential oils compared to chlorhexidine with respect to plaque and parameters of gingival inflammation: a systematic review

BACKGROUND

The purpose of this review is to systematically evaluate the effects of an essential-oil mouthwash (EOMW) compared to a chlorhexidine mouthwash with respect to plaque and parameters of gingival inflammation.

METHODS

PubMed/MEDLINE and Cochrane CENTRAL databases were searched for studies up to and including September 2010 to identify appropriate articles. A comprehensive search was designed, and the articles were independently screened for eligibility by two reviewers. Articles that evaluated the effects of the EOMW compared to chlorhexidine mouthwash were included. Where appropriate, a meta-analysis was performed, and weighted mean differences (WMDs) were calculated.

RESULTS

A total of 390 unique articles were found, of which 19 articles met the eligibility criteria. A meta-analysis of long-term studies (duration ≥ 4 weeks) showed that the chlorhexidine mouthwash provided significantly better effects regarding plaque control than EOMW (WMD: 0.19; P = 0.0009). No significant difference with respect to reduction of gingival inflammation was found between EOMW and chlorhexidine mouthwash (WMD: 0.03; P = 0.58).

CONCLUSION

In long-term use, the standardized formulation of EOMW appeared to be a reliable alternative to chlorhexidine mouthwash with respect to parameters of gingival inflammation.

Health-Beneficial Phenolic Aldehyde in Antigonon leptopus Tea

Tea prepared from the aerial parts of Antigonon leptopus is used as a remedy for cold and pain relief in many countries. In this study, A. leptopus tea, prepared from the dried aerial parts, was evaluated for lipid peroxidation (LPO) and cyclooxygenase (COX-1 and COX-2) enzyme inhibitory activities. The tea as a dried extract inhibited LPO, COX-1 and COX-2 enzymes by 78%, 38% and 89%, respectively, at 100 μg/mL. Bioassay-guided fractionation of the extract yielded a selective COX-2 enzyme inhibitory phenolic aldehyde, 2,3,4-trihydroxy benzaldehyde. Also, it showed LPO inhibitory activity by 68.3% at 6.25 μg/mL. Therefore, we have studied other hydroxy benzaldehydes and their methoxy analogs for LPO, COX-1 and COX-2 enzymes inhibitory activities and found that compound 1 gave the highest COX-2 enzyme inhibitory activity as indicated by a 50% inhibitory concentration (IC(50)) at 9.7 μg/mL. The analogs showed only marginal LPO activity at 6.25 μg/mL. The hydroxy analogs 6, 7 and 9 showed 55%, 61% and 43% of COX-2 inhibition at 100 μg/mL. However, hydroxy benzaldehydes 3 and 12 showed selective COX-1 inhibition while compounds 4 and 10 gave little or no COX-2 enzyme inhibition at 100 μg/mL. At the same concentration, compounds 14, 21 and 22 inhibited COX-1 by 83, 85 and 70%, respectively. Similarly, compounds 18, 19 and 23 inhibited COX-2 by 68%, 72% and 70%, at 100 μg/mL. This is the first report on the isolation of compound 1 from A. leptopus tea with selective COX-2 enzyme and LPO inhibitory activities.

Antibacterials as anti-inflammatory agents: dual action agents for oral health

BACKGROUND

Inflammatory processes with a range of specialized cells and biochemical mediators form a complex network of inter-related signal transducing pathways that relay information to preserve normal functions. Advances in molecular analyses of the information relay pathways for their constituents and principal ligands along with mechanisms utilized by the host for microbial recognition have stimulated interest in therapeutic agents with dual functionalities i.e. antibacterial and anti-inflammatory effects.

AIM

This review examines clinically tested agents for oral health applications with both antimicrobial and anti-inflammatory effects to include antibiotics, antimicrobials and phenolics.

RESULTS

Bis-phenols such as triclosan, representing a unique dual functional therapeutic for routine oral hygiene, with its demonstrated clinical effects on inhibiting the dental plaque biofilm, reducing inflammation (gingivitis) and subsequent periodontitis is described. Cyclines, comprising another class of approved anti-inflammatory agents used at the patient level for oral health is discussed. Dual active agents in current clinical practice for systemic conditions are highlighted to summarize the clinical validity of dual function agents as an emerging therapeutic strategy.

CONCLUSIONS

Clinical studies demonstrate therapeutic benefits of agents with dual functionality with their effects on microorganisms and the concomitant host inflammatory response. Advances in microbial pathogenesis and resultant inflammation will facilitate progress in this emerging area poised to be a significant milestone for dental therapeutics.

Acetaminophen inhibits prostanoid synthesis by scavenging the PGHS-activator peroxynitrite

The primary pharmacological target of acetaminophen is prostaglandin endoperoxide H2 synthase (PGHS). The enzymatic catalytic mechanism is radical-based, initiated, and maintained by the persistent presence of peroxides, particularly peroxynitrite, which is termed "peroxide tone". Whereas the prevailing concept assumes a direct reduction of the active, oxidized enzyme by acetaminophen, here we show that acetaminophen is a potent scavenger of peroxynitrite (peroxynitrite-mediated phenol nitration, IC50 approximately 72 microM; Sin-1-mediated DHR123 oxidation, IC50 approximately 11 microM) and thus inhibits PGHS by eliminating the peroxide tone. Nanomolar concentrations of peroxynitrite increased the activity of isolated PGHS and prostacyclin formation by aortic endothelial cells. This elevated activity was efficiently inhibited by pharmacologically relevant concentrations of acetaminophen (IC50 approximately 10 microM for 6-keto-PGF1alpha) and other free radical scavengers. However, when the peroxide tone was provided by H2O2 or tert-butyl-OOH, acetaminophen had only negligible inhibitory effects. Our concept could help to explain the efficacy of acetaminophen to inhibit PGHS in cell types with moderate oxidant formation. However, high levels of peroxynitrite or other peroxides such as lipid peroxides formed at inflammatory sites might overwhelm the ability of acetaminophen to decrease PGHS activation. The concept presented herein provides a molecular basis to explain the excellent analgesic and antipyretic properties of acetaminophen together with its minimal anti-inflammatory effects.

Eugenol suppressed the expression of lipopolysaccharide-induced proinflammatory mediators in human macrophages

Eugenol is commonly used as an analgesic agent during acute pulpitis and is a major component of root canal sealers. Despite the frequent applications of eugenol in the practice of dentistry, little is known about the role of eugenol under the status of inflammation. This study was aimed to investigate the influence of eugenol on human macrophages (U937) under the stimulation of lipopolysaccharide (LPS). Eugenol was shown to block the release of the bone resorbing mediators, including interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and prostaglandin E2 from LPS-stimulated macrophages. In contrast, eugenol alone did not alter the expression levels of these proinflammatory mediators in macrophages. Consistent with downregulation of bone-resorbing mediators, eugenol suppressed the messenger RNA expression of LPS-induced IL-1beta, TNF-alpha, and cyclooxygenase-2 in macrophages. The results suggest a potential anti-inflammatory effect of eugenol in the acute inflamed pulps and apical periodontitis.

Anti-Inflammatory Activity of Thymol: Inhibitory Effect on the Release of Human Neutrophil Elastase

Elastase, a serine proteinase released by activated human neutrophils, can degrade a wide variety of biomacromolecules including elastin, and is considered a marker of inflammatory diseases. As the logical strategy to protect tissue is to inhibit excessive elastase activity, experimental and clinical researches have concentrated on trying to find efficient elastase inhibitors. As thymol, one of the major components of thyme oil with a phenolic structure, has been credited with a series of pharmacological properties, that include antimicrobial and antioxidant effects, the aim of this study was to explore whether it can also interfere with the release of elastase by human neutrophils stimulated with the synthetic chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP). After the neutrophils were incubated with increasing amounts of thymol (2.5, 5, 10, 20 microg/ml), elastase release was initiated by fMLP and measured using MeO-Suc-Ala-Ala-Pro-Val-MCA. The results showed that thymol inhibited fMLP-induced elastase release in a concentration-dependent manner, with the effects of 10 and 20 microg/ml being statistically significant. The behavior of cytosolic calcium mobilization revealed by fura-2 closely resembled that of elastase, thus suggesting that they may be related. The hydrophobic nature of thymol means that it can approach ion channel proteins through the lipid phase of the membrane, alter the local environment of calcium channels and thus inhibit capacitative calcium entry. In brief, thymol inactivates calcium channels machinery, thus triggering a corresponding reduction in elastase. The antibacterial and antimycotic activity of thymol is already well known, but our findings that it inhibits elastase extend our knowledge of the anti-inflammatory activity of this interesting molecule that is already credited with antioxidant activity. These two latter characteristics make thymol a molecule that can have helpful effects in controlling the inflammatory processes present in many infections.

Antioxidant Potential of Thymol Determined by Chemiluminescence Inhibition in Human Neutrophils and Cell-Free Systems

Thyme essential oil and thymol have antimicrobial, antifungal and antioxidant activities. Their antioxidant activity has been studied almost exclusively by means of chemical testing in order to be able to use it for food preservation purposes. The aim of this luminol amplified chemiluminescence (LACL) study was to investigate whether thymol can interfere with the production of reactive oxygen species, nitric oxide and the nitric oxide-derived peroxynitrite released by human neutrophils after activation by fMLP and PMA with and without the addition of the L-arginine (L-Arg) nitric oxide donor to the medium. The lowest thymol concentration that was still active in reducing LACL was 2.73 microg/ml, and there was a progressive linear inhibition of LACL from this concentration to 21.87 microg/ml, the highest thymol concentration investigated. This was also observed in the case of both fMLP and PMA stimulation with or without L-Arg. In cell-free systems using H(2)O(2)/HOCl(-) and SIN-1 as radical producers, a significant scavenging activity of thymol was present already at 0.08 and 0.68 microg/ml respectively, and these are very low concentrations. These findings can be related to the phenolic structure of thymol, because phenolic compounds have redox properties and play an important role in adsorbing and neutralizing free radicals and peroxynitrite, and in decomposing peroxides. Our findings in human neutrophils are pharmacologically relevant as they imply that thymol is a potential antioxidant and anti-inflammatory agent in human cells.

Hydroxyl radical scavenging effects of guaiacol used in traditional dental pulp sedation: reaction kinetic study

Guaiacol, which is a phenolic compound with a methoxy group and used in traditional dental pulp sedation, has the property of inducing cell proliferation. To clarify these mechanisms of guaiacol, this study examined the hydroxyl radical (*OH) scavenging effects of guaiacol in vitro. Generation of *OH was carried out by the Fenton reaction using mixture of ascorbic acid, H2O2, and Fe(III)-EDTA, and *OH was detected by measuring the *OH-mediated production of degradation products of deoxyribose, which reacts with 2-thiobarbituric acid (TBA) and is relatively stable for a long time. At concentrations of 10(-10) M to 10(-3) M, guaiacol inhibited the TBA reactive substance (TBA-RS) formation in a dose-dependent manner. Phenol and formaldehyde were also found to inhibit the TBA-RS formation, but their inhibitory activities were lower than that of guaiacol. The concentrations of guaiacol, phenol, and formaldehyde needed to cause 50% inhibition of TBA-RS formation were approximately 5 x 10(-6), 5 x 10(-5), and 2 x 10(-3) M, respectively. In this reaction system, guaiacol showed no chelating reaction with ferrous ion and did not directly react with H2O2. Guaiacol also exhibited radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) stable free radical, but its scavenging activity was lower than that toward *OH. These results suggest that guaiacol is a potent scavenger of reactive oxygen radicals and that its radical scavenging activity may be associated with its effect on cell proliferation.

The effect of a mouth rinse containing phenolic compounds on plaque formation and developing gingivitis

BACKGROUND

The clinical effect of Listerine, a mouth rinse containing a mixture of phenolic compounds, is ascribed to its bactericidal properties. However, phenolic compounds are also known to interfere with the inflammatory process.

OBJECTIVE

The purpose of this clinical trial was to evaluate the effect of regular mouth rinsing with Listerine on plaque and gingivitis during a 2-week period of no mechanical oral hygiene.

MATERIAL AND METHODS

Twenty-one subjects were recruited for the study. On Day 0 of each 2-week experimental period, the participants were told to abstain from all mechanical plaque-control measures but to rinse twice a day with 10 ml of the assigned solution (test: Listerine, positive control:0.1% chlorhexidine (CHX), negative control: saline) for 60 s. Each experimental period was preceded by a 2-week period including oral hygiene instruction, scaling and professional mechanical tooth cleaning. Examinations included assessments of plaque and gingivitis (Days 0 and 14), sampling of plaque and collection of gingival crevicular fluid (GCF) (Days 0, 7 and 14). From the supragingival plaque samples, six different morphotypes of bacteria were counted using dark-field microscopy. The GCF collected was analysed with respect to the content of lactoferrin and albumin.

RESULTS

During the experimental periods, it was observed that significantly less plaque formed and less gingivitis developed when the participants rinsed with the Listerine mouthwash than with saline solution. However, significantly more plaque formed during the Listerine than during the CHX rinse period, while there was no significant difference in the development of gingival bleeding between the Listerine and the CHX rinse regimens. Significantly smaller proportions of motile rods and fusiforms were found in the List and CHX groups than in the control (Ctrl) group. The increase of the lactoferrin/albumin ratio in the List group was significantly smaller than that in the Ctrl group but significantly larger than in the CHX group.

CONCLUSION

It was suggested that the effect of Listerine on gingivitis is more pronounced than on plaque formation. This indicates that the phenolic compound may have anti-inflammatory effects.

Anti-inflammatory activity of 1.8-cineol (eucalyptol) in bronchial asthma: a double-blind placebo-controlled trial

Airway hypersecretion is mediated by increased release of inflammatory mediators and can be improved by inhibition of mediator production. We have recently reported that 1.8-cineol (eucalyptol) which is known as the major monoterpene of eucalyptus oil suppressed arachidonic acid metabolism and cytokine production in human monocytes. Therefore, the aim of this study was to evaluate the anti-inflammatory efficacy of 1.8-cineol by determining its prednisolone equivalent potency in patients with severe asthma. Thirty-two patients with steroid-dependent bronchial asthma were enrolled in a double-blind, placebo-controlled trial. After determining the effective oral steroid dosage during a 2 month run-in phase, subjects were randomly allocated to receive either 200 mg 1.8-cineol t. i.d. or placebo in small gut soluble capsules for 12 weeks. Oral glucocorticosteroids were reduced by 2.5 mg increments every 3 weeks. The primary end point of this investigation was to establish the oral glucocorticosteroid-sparing capacity of 1.8-cineol in severe asthma. Reductions in daily prednisolone dosage of 36% with active treatment (range 2.5-10 mg, mean: 3.75 mg) vs. a decrease of only 7% (2.5-5 mg, mean: 0.91 mg) in the placebo group (P = 0.006) were tolerated. Twelve of 16 cineol vs. four out of 16 placebo patients achieved a reduction of oral steroids (P = 0.012). Long-term systemic therapy with 1.8-cineol has asignificant steroid-saving effect in steroid-depending asthma. This is the first evidence suggesting an anti-inflammatory activity of the monoterpene 1.8-cineol in asthma and a new rational for its use as mucolytic agent in upper and lower airway diseases.

Biocompatibility of dental materials used in contemporary endodontic therapy: a review. Part 2. Root-canal-filling materials

Root-canal-filling materials are either placed directly onto vital periapical tissues or may leach through dentine. The tissue response to these materials therefore becomes important and may influence the outcome of endodontic treatment. This paper is a review of the biocompatibility of contemporary orthograde and retrograde root-canal-filling materials.

Screening of ubiquitous plant constituents for COX-2 inhibition with a scintillation proximity based assay

A rapid semi-homogeneous cyclooxygenase-2 (COX-2) enzymatic assay using scintillation proximity assay (SPA) technology was developed, and 49 ubiquitous plant secondary metabolites were screened for inhibition of COX-2-catalyzed prostaglandin E(2) (PGE(2)) biosynthesis. Assay conditions were optimized with respect to reaction time, amount of antibody, radiolabeled PGE(2), and SPA beads, and the kinetic parameter, K(m), was estimated. The assay was validated with two natural triterpenoids, ursolic and oleanolic acid, known to inhibit COX-2, as well as with four synthetic COX inhibitors, NS-398, rofecoxib, indomethacin, and aspirin. Plant metabolites of different biosynthetic origin representing several substance classes, including alkaloids, anthraquinones, flavonoids, phenylpropanes, steroids, and terpenes, were screened for inhibition of COX-2-catalyzed PGE(2) production. Of these 49 plant metabolites, eugenol, pyrogallol, and cinnamaldehyde (with IC(50) values of 129, 144, and 245 microM, respectively) were found to inhibit COX-2. This study showed that a COX-2-catalyzed PGE(2) assay using SPA is suitable for screening natural compounds with respect to COX-2 inhibition.

Comparative QSAR: on the toxicology of the phenolic OH moiety

In this report we consider the effect of substituents on phenol toxicity and show how the parameters used in Quantitative Structure-Activity Relationships (QSAR) can be used to draw mechanistic inferences of value in understanding the reasons behind the various types of toxicity. In particular, we are interested in gaining clearer insight into mechanisms via the Hammett-type parameters sigma, sigma(-), sigma(+) and octanol/water parti tion coefficients. Particular attention is given to the role of radical reactions and their role in attacking DNA to cause cancer or estrogenic toxicity.

Prostaglandin H synthase. Effects of peroxidase cosubstrates on cyclooxygenase velocity

Many cosubstrates for the peroxidase activity of prostaglandin H synthase-1 (PGHS-1) have been reported to produce a large (2-7-fold) increase in the cyclooxygenase velocity in addition to a substantial increase in the number of cyclooxygenase catalytic turnovers. The large stimulation of cyclooxygenase velocity has become an important criterion for evaluation of putative PGHS reaction mechanisms. This criterion has been a major weakness of branched-chain tyrosyl radical mechanisms, which correctly predict many other cyclooxygenase characteristics. Our computer simulations based on a branched-chain mechanism indicated that the uncorrected oxygen electrode signals commonly used to monitor activity can seriously overestimate the effects of cosubstrate on cyclooxygenase velocity. The simulation results prompted re-examination of the effect of several cosubstrates (phenol, acetaminophen, N,N,N',N'-tetramethylphenylenediamine, and Trolox) on PGHS-1 cyclooxygenase velocity. Cyclooxygenase kinetics were examined at reduced temperature or elevated pH, where the oxygen electrode signal can be corrected to provide reliable oxygen consumption trajectories. The cosubstrates produced only a slight (10-60%) stimulation of the cyclooxygenase velocity. Peroxidase cosubstrates thus have a much smaller stimulatory effect on cyclooxygenase velocity than previously reported. This corrects a longstanding misperception of cosubstrate effects, provides more realistic kinetic constraints on PGHS mechanisms, and removes what was a major deficiency of branched-chain tyrosyl radical mechanisms.

Mechanism of action in a 4,5-diarylpyrrole series of selective cyclo-oxygenase-2 inhibitors

Using semi-empirical AM1 calculation and 6.31G* basis sets, we have calculated the energy of the highest-occupied molecular orbital (E(HOMO)) for anti-inflammatory 4,5-diarylpyrroles which have been shown to have inhibitory activity on cyclooxygenase COX-2, an inducible enzyme expressed during inflammation. We have found a correlation between the E(HOMO) of a molecule and its COX-2 inhibition. However, no correlation was observed between E(HOMO) and the inhibition efficiency of cyclooxygenase-1 (COX-1), the constitutively expressed enzyme, protective to the organism. This result suggests that the inhibitions of the two isoforms follow different molecular mechanisms.

Synthesis and biological activity of aspirin derivatives

Aspirin has been widely used as analgesic and anti-inflammatory drug. Recently, it was elucidated that aspirin have anti-coaggregatory effect in low dose. This study was carried out to investigate the synthesis of aspirin derivatives from aspirin and aromatic compound of antioxidant and its biological activities. Synthesis of aspirin derivatives was prepared by esterification in the presence of 1,1-carbonyldiimidazole. Biological activities was examined using effect of anti-coagulant on bleeding time, effect of antioxidant and effect of anti-platelet aggregation. As a result, SJ-101 showed strong antioxidative activity and anti-coagulant activity among four compounds. Anti-platelet aggregation of SJ-101 was examined by collagen, ADP, PAF method. SJ-101 exhibited more stronger activity to aspirin at collagen aggregation reaction. These finding demonstrates that SJ-101 is useful as care drug of aging and old-disease because of its has antioxidant activity, anti-coagulant activity and anti-platelet activity.

6-(Hydroxyphenyl)imidazo[2,1-b]thiazoles as Potential Antiinflammatory Agents: Effects on Human Neutrophil Functions

Synthesis of 6-(hydroxyphenyl)imidazo[2,1-b]thiazoles related to levamisole from the corresponding methoxy derivatives is reported. These compounds were tested on in vitro neutrophil activation, namely locomotion induced by chemoattractants, superoxide generation and lysozyme degranulation triggered by agonists. These functions were evaluated after cell pulse with different concentrations of the drugs. Several derivatives showed significant inhibitory effects, in some cases more potent than the parent compound.

Scavenging effect of benzophenones on the oxidative stress of skeletal muscle cells

Benzophenone is an ultraviolet (UV)-absorbing agent that has been used in industry and medicine for more than 30 years. Consumers of cosmetics and sunscreens containing UV-absorbers are exposed to benzophenones on a daily basis, owing to the widespread use of these compounds. However, the efficacy of these compounds as scavengers of oxidative stress is still not well established. In the present study, we investigate the antioxidative capacity of six sunscreen benzophenone compounds. A primary myoblast culture was mixed in vitro with 100 microM menadione. The cytotoxic effect by menadione-induced oxidative stress was monitored by the lucigenin- or luminol-amplified chemiluminescence, methylthiotetrazole (MTT) assay, and the antioxidative effects of various benzophenone compounds were evaluated. The results showed that the addition of menadione can induce oxidative stress on myoblasts by superoxide and hydrogen peroxide production, which can be eradicated by superoxide dismutase (SOD) and catalase, respectively, in a dose-dependent mode. The catalase has a protective effect on the cytotoxicity induced by menadione as measured by the MTT assay, while the SOD does not. The selected benzophenones also have a significant scavenging effect on the menadione-induced cell death on the myoblasts. The ortho-dihydroxyl structure and other hydroxy groups in the same ring have a stronger scavenging effect on the superoxide anion on myoblasts; thus, a stable penoxy radical may be formed. The mechanism of this effect remains to be clarified.

Molecular orbital theory applied to the study of nonsteroidal anti-inflammatory drug efficiency

Using a simple quantum mechanical method, we calculated the energy of the highest-occupied molecular orbital (E(HOMO)) of three groups of anti-inflammatory compounds, and we have found correlations between E(HOMO) of these molecules and experimental data previously reported on (1) inhibition of sheep-vesicular-gland prostaglandin cyclooxygenase by phenolic compounds, (2) inhibition of prostaglandin cyclooxygenase in mouse macrophages by salicylates, benzoates and phenols, and (3) peroxyl-radical scavenging and radioprotection of a bacterial virus by NSAID drugs, including metiazinic acid, sulindac, D-penicillamine, piroxicam, indomethacin, benoxaprofen, and aspirin. Our correlations using a systematic evaluation of the HOMO energies can be of predictive value in the search for new anti-inflammatory drugs as well as for new radioprotectors.

Effect of an antibacterial dental varnish on the levels of prostanoids, leukotriene B4, and interleukin-1 beta in gingival crevicular fluid

The aim of this study was to investigate the effects of a chlorhexidine/thymol-containing dental varnish on the levels of prostaglandin E2 (PGE2), prostaglandin I2 (PGI2), leukotriene B4 (LTB4), and interleukin-1 beta (IL-1 beta) in gingival crevicular fluid (GCF). The material consisted of 15 adolescents undergoing treatment with fixed orthodontic appliances. Four buccal sites adjacent to bands or brackets and exhibiting a mild chronic gingival inflammation were selected in the upper quadrants of each patient. According to a split-mouth technique, the first and second quadrants were randomly treated with either a varnish (Cervitec) containing 1% chlorhexidine diacetate and thymol (CHX/thymol) or a placebo varnish without active ingredients. The varnishes were applied immediately after the baseline registration, and follow-up examinations were carried out after 3, 8, and 30 days. GCF was sampled with the aid of a paper strip and the volume was determined using a Periotron 8000. The concentrations of PGE2, PGI2, LTB4, and IL-1 beta in GCF were assessed using radioimmunoassay and ELISA techniques. The results unveiled statistically significant reductions of PGE2, PGI2, and LTB4 levels in GCF following the active varnish treatment when compared to baseline values. A slight drop in IL-1 beta levels was registered after both active and placebo varnish applications, but the differences were not significant. The results suggest that treatment with an antibacterial varnish decreases the levels of inflammatory mediators PGE2, PGI2, and LTB4 in gingival crevicular fluid and further support the concept that topical application of a CHX/thymol-containing varnish is beneficial in patients with chronic gingival inflammation.

Modulation of arachidonic acid metabolism by phenols: relation to their structure and antioxidant/prooxidant properties

The effects of substituted catechols (3-methylcatechol, 4-methylcatechol, 4-nitrocatechol, and guaiacol) and trihydroxybenzenes (pyrogallol, propyl gallate, 1,2,4-trihydroxybenzene, and 1,3,5-trihydroxybenzene) on the synthesis of prostaglandin (PG)E2 and leukotriene (LT)B4 were tested in human A23187-stimulated polymorphonuclear leukocytes. The effects were related to their peroxyl-radical-scavenging (antioxidant), superoxide-scavenging (antioxidant), and superoxide-generating (prooxidant) properties. In general, compounds with hydroxyl groups in the ortho position increased PGE2/LTB4 ratio, and compounds with hydroxyl groups in the meta position decreased PGE2/LTB4 ratio. Catechols, which have hydroxyl groups in the ortho position, were the most potent peroxyl radical and superoxide anion scavengers. Trihydroxybenzenes (pyrogallol, 1,2,4-trihydroxybenzene, and 1,3,5-trihydroxybenzene) generated superoxide, whereas dihydroxybenzenes did not. Thus, the positions and number of hydroxyl groups seem to be the most important properties determining the action of phenolic compounds on PGE2/LTB4 ratio and their antioxidant/prooxidant activities.

Eugenol diffusion through dentin related to dentin hydraulic conductance

OBJECTIVES

The purpose of this study was (1) to find an easy way of evaluating the concentration of eugenol in cell culture fluids; (2) to confirm the relationship between the concentration and the cytotoxicity of eugenol in vitro; (3) to evaluate the cytotoxicity of four temporary eugenol-based filling materials: IRM, super EBA, Kalsogen and zinc oxide-eugenol cement; and (4) to establish a relationship between dentin permeability, eugenol diffusion and cytotoxicity.

METHODS

(1) The concentration of eugenol was measured with a spectrofluorimeter; (2) the cell viability of L 929 cells cultivated for 24 h with eugenol-containing medium was evaluated by the MTT assay; (3) after measurement of hydraulic conductance, occlusal cavities in human teeth in vitro were filled with the restorative materials. The cytotoxicity was measured with undiluted test medium and with various dilutions in culture medium; (4) after Lp measurement, the eugenol concentration in the media in the pulp chamber that diffused from IRM and 10(3) mol/l eugenol solution was measured.

RESULTS

(1) A proportional relationship (p = 0.001 and r = 1) was found between the concentration of eugenol; (2) eugenol started to be cytotoxic at 10(-5) mol/l and killed 95% of the cells at 10(-3) mol/l; (3) zinc oxide-eugenol cement was the most cytotoxic filling material when tested with the 1:100 dilution; (4) a significant relationship was found between Lp and cytotoxicity (p = 0.04) depending on the dilution of the test medium. A significant relationship was found between Lp and eugenol diffusion from a 10(-3) mol/l solution (p = 0.03) but not between Lp and eugenol diffusing from solid IRM (non significant).

SIGNIFICANCE

Eugenol diffusion from zinc oxide-eugenol cement appears to depend more on the role of hydrolysis of eugenol from zinc oxide-eugenol cement than on dentin permeability.

Phenol toxicity in leukemia cells: a radical process?

The multiple functions of the phenol moiety that are widely present in disparate sources such as drugs, pesticides, teas, fuel additives and surfactants have not been clearly delineated. The differences in behavior of phenols, which run the gamut from aberrations in DNA/chromosomes to suppression of genotoxic activity of carcinogenic compounds, merit further attention. In this study, a through examination of the growth inhibition patterns of 37, simple 3- and 4-substituted phenols in mouse leukemia cells was carried out and the following quantitative structure-activity relationship (QSAR) was obtained for the 23 electron releasing substituents in X-phenols: log 1/IC50 = -1.58 sigma(+) +0.21 log P + 3.10. In this QSAR, IC50 is the concentration of phenol that induces 50% inhibition of growth. P is a measure of the hydrophobicity of each phenol and Brown's electronic parameter, sigma+, represents the electronic effect of the substituent. The negative dependence on sigma+ is strongly reminiscent of what is observed in the developmental toxicity of phenols on rat embryos as well as for the radical abstraction of a hydrogen atom from phenolic groups. The other 15 electron-attracting substituted X-phenols clearly show a linear dependence on hydrophobicity alone: Log 1/IC50 = 0.62 log P + 2.35. The bifurcation in mechanism of action of this large set of diverse phenols is novel and unusual. It suggests that two distinct processes are operative. In the case of electron releasing substituted phenols, the observations are not inconsistent with a radical mediated process while with electron attracting substituted phenols, non-specific toxicity as modulated by hydrophobicity, appears to predominate.

Short-term effects of triclosan on healing following subgingival scaling

The present clinical trial was performed to evaluate short-term effects of a triclosan-containing dentifrice/gel combination on soft tissue healing, when applied supra-/sub-gingivally at periodontal sites treated with scaling and root planing. 16 subjects with moderate periodontitis participated in a 2x 2-week, split-mouth designed clinical trial. 2 combinations of gel/dentifrice (the test combination containing triclosan) were used. 2 pairs of contralateral sites with probing pocket depth (PPD) > or 5 mm, and which bled on probing (BoP +) were selected in each patient as experimental units. A baseline examination included assessments of PPD, BoP, gingival index scores, plaque index scores, and the composition of the subgingival microbiota (dark-field microscopy). The assigned quadrant was anaesthetized and the teeth exposed to meticulous scaling and root planing. Immediately after the completion of mechanical therapy, either the test or control gel was applied subgingivally at the experimental sites. The volunteer was instructed to brush his/her teeth with an assigned dentifrice and to apply the gel (via a custom-made stent) supra-gingivally 2x daily for the following 2 weeks. He/she was recalled on day 7 for a second professional subgingival gel application. Re-examinations were carried out on days 2, 7 and 14 after treatment. 1-week wash-out periods separated the 2 experimental periods. The mean PPD reductions (between days 0 and 14) were 1.8 mm and 1.9 mm for the test and control gel/dentifrice sites. The reduction in BoP and gingival index scores was significantly greater during the test than during the control regimen. No significant differences were observed between the 2 regimens regarding plaque scores and composition of the subgingival microbiota. The findings from the present investigation demonstrated that triclosan, applied both sub- and supra-gingivally reduced soft tissue inflammation following scaling and root planing.

Does the nature of the solvent affect the anti-inflammatory capacity of triclosan? An experimental study

The anti-inflammatory properties of triclosan have been revealed in several recent studies, including an effect on histamine-induced inflammation. In other studies, the nature of the solvent has been shown to be of importance for the plaque inhibiting as well as the antibacterial potential of triclosan. This study was aimed at examining whether the nature of the solvent also may influence the anti-inflammatory capacity of triclosan and further to study a possible dose/ response relationship. The study was performed as 3 separate, double-blind experiments, comprising 10, 11 and 12 healthy females. In all 3 experiments, 5 sites on the lower part of the back of the volunteers were intradermally exposed to one drop of 1% histamine dihydrochloride for 15 min. The size of the resulting wheals was recorded before and after 40 min of triclosan treatment. In experiment 1, 4 different concentrations of triclosan in 2-fold dilutions in absolute alcohol (0.125%-1%) were applied on the histamine-induced wheals. In experiments 2 and 3, 4 different solutions containing 0.5% triclosan and a saline solution as negative control were used. The solvents in experiment 2 were as follows: (1) absolute alcohol (positive control), (2) propylene glycol (PG), (3) polyethylene glycol (PEG), (4) olive oil, and in experiment 3: (1) absolute alcohol (positive control), (2) Tween 80, (3) sodium carbonate, (4) soy oil. The results showed a dose/ response effect of triclosan and further that the solvent may be of importance for its anti-inflammatory potential.

In vitro evaluation of the cytotoxicity of pure eugenol

The aim of this study was to assess the cytotoxicity of pure eugenol in an in vitro method by diluting it to various concentrations in alcohol and determining the maximum noncytotoxic concentration. We used solutions of eugenol and ethyl alcohol that are soluble in water in any given proportion. The cytotoxicity of the alcohol itself was determined by using a dose-response curve for concentrations of between 0.017 M and 1.7 M. Various strength concentrations (0.015 to 947 microM) of eugenol in alcohol were prepared; 20 microliters (0.34 M) of ethyl alcohol was added to 1 ml of cell medium. The experiment showed that pure eugenol is toxic for human gingival fibroblasts. Eugenol in an alcohol solution at concentrations of < 1.9 microM is noncytotoxic.

hP, the component of log P controlling structure-activity relationships amongst non-steroidal anti-inflammatory drugs

A range of 25 drugs and other compounds selected from published sources by strict criteria, has been used to confirm that their ability to inhibit the production of prostaglandin by mouse peritoneal macrophage does not correlate with log P but with hP, the parameter composed of only the hydrophobic contributions (atoms and groups composed of carbon, hydrogen and halogens). Other heteroatoms and physical properties can usually be ignored. Anti-inflammatory activity does not depend upon pKa or partition phenomena unless extreme, nor does it depend primarily upon the structural types within the range phenols, salicylic acids, mefenamic acids, areneacetic and profenic acids.

Plant phenolics as potential cancer prevention agents

The frequent consumption of fresh fruits and vegetables is associated with a lower cancer incidence in humans, and in experimental carcinogenesis. There are several groups of substances in plant foods which may contribute to this inhibition of tumor development. Almost all fresh fruits, vegetables and cereal grains contain appreciable amounts of naturally occurring plant phenolics. A brief overview will be presented of the most common plant phenolics in human foods and their chemical and biochemical properties. Plant phenolics, originally hypothesized to inhibit mutagenesis and/or carcinogenesis by virtue of antioxidant or electrophile trapping mechanisms, can also act as potent modulators of arachidonic metabolism cascade pathways. Certain plant phenols can be effective inhibitors of chemical mutagens, in vitro, and/or carcinogenesis in vivo. The historical origins, hypotheses of actions, current status and potential adverse effects of the utility of plant phenolics to reduce risk of cancer are discussed, as well as future possibilities and needs and objectives for future research.

Sodium nonivamide acetate: a non-pungently antinociceptive capsaicin derivative with unusual anti-inflammatory properties

1. Bradykinin-induced vascular pain in conscious rats, hyperalgesia in the rat hind paw, rat hind paw edema induced by compound 48/80 and carrageenin and dye exudation induced by intraperitoneal injection of 0.7% acetic acid in mice were all inhibited by sodium nonivamide acetate (SNA). 2. Collagen and arachidonic acid-induced rabbit platelet aggregations were inhibited by SNA and capsaicin. In human platelet microsomes, prostaglandin E2 formation in arachidonic acid metabolite was not inhibited by SNA but was inhibited by capsaicin and indomethacin; thromboxane B2 formation and its synthetase activity were inhibited by SNA and capsaicin. 3. In the extracellular recording, SNA could not decrease the action potential amplitude of the vagus nerve. 4. The motor activity of mice induced by caffeine (1.0 mg/kg) was inhibited by SNA and capsaicin.

The effect of triclosan on mediators of gingival inflammation

Triclosan (2,4,4',-trichloro-2'-hydroxydiphenylether) is a well-known and widely used nonionic antibacterial agent which has recently been introduced in toothpastes and mouthrinses. The efficacy of triclosan-containing toothpaste and mouthrinse to reduce both plaque and gingivitis in long-term clinical trials has been well documented. Until recently, it was generally assumed that triclosan's effect on gingival inflammation was due to its antimicrobial and anti-plaque effect. It has now become apparent that triclosan may have a direct anti-inflammatory effect on the gingival tissues. Several in vitro studies were conducted to evaluate the effect of triclosan on 4 primary enzymes of the pathways of arachidonic acid metabolism, cyclo-oxygenase 1, cyclo-oxygenase 2, 5-lipoxygenase and 15-lipoxygenase. These pathways lead to the production of known mediators of inflammation such as the prostaglandins, leukotrienes and lipoxins. Triclosan inhibited both cyclooxygenase 1 and cyclo-oxygenase 2 with IC-50 values of 43 microM and 227 microM, respectively. Triclosan also inhibited 5-lipoxygenase with an IC-50 of 43 microM. The 15-lipoxygenase was similarly inhibited by triclosan with an IC-50 of 61 microM. Hence, triclosan has the ability to inhibit both the cyclo-oxygenase and lipoxygenase pathways of arachidonic acid metabolism with similar efficacy. In cell culture experiments, it was found that triclosan inhibited IL-1 beta induced prostaglandin E2 production by human gingival fibroblasts in a concentration dependent manner, and at relatively low concentrations. These data, taken together, indicate that triclosan can inhibit formation of several important mediators of gingival inflammation.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of triclosan on developing gingivitis

The aim of the study was to examine whether triclosan has an effect on developing gingival inflammation. 10 volunteers, with clinically healthy gingivae were enrolled. The study was performed as a 2-week, double-blind, cross-over, experimental gingivitis trial. Between each plaque accumulation period, there was a wash-out phase of 4 weeks. A baseline examination was performed which included assessment of plaque and gingivitis. The volunteers were asked to refrain from mechanical oral hygiene measures for 2 weeks. During this period, they rinsed 2x daily with one of the randomly assigned mouthrinse preparations. Solution A (period A): 0.06% triclosan+ 2%tween 80. Solution B (period B): 0.06% triclosan+ 0.25% sodium lauryl sulphate. Re-examinations were performed on days 4, 7, 11 and 14. The mean plaque score increased during period A to 2.2 (day 4), 2.8 (day 7), 3.1 (day 11) and 3.1 (day 14). The corresponding scores for period B were significantly lower; 1.2 (day 4), 1.8 (day 7), 2.0 (day 11) and 2.2 (day 14). The mean gingivitis scores at baseline were 0.17 (periods A and B). The mean gingivitis scores increased to 0.45 (day 4), 0.69 (day 7), 0.83 (day 11) and 0.96 (day 14) when the subjects rinsed with solution A and 0.42 (day 4), 0.64 (day 7), 0.78 (day 11) and 0.92 (day 14) in period B. There were no statistically significant differences between periods A and B with respect to gingivitis. Thus, although significantly more plaque formed during period A than period B, no differences could be found between the gingivitis scores in the 2 periods.