Effect of two flavonoid compounds on central nervous system. Analgesic activity

Antinociceptive effects of minor cannabinoids, terpenes and flavonoids in Cannabis

Cannabis has been used for centuries for its medicinal properties. Given the dangerous and unpleasant side effects of existing analgesics, the chemical constituents of Cannabis have garnered significant interest for their antinociceptive, anti-inflammatory and neuroprotective effects. To date, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) remain the two most widely studied constituents of Cannabis in animals. These studies have led to formulations of THC and CBD for human use; however, chronic pain patients also use different strains of Cannabis (sativa, indica and ruderalis) to alleviate their pain. These strains contain major cannabinoids, such as THC and CBD, but they also contain a wide variety of cannabinoid and noncannabinoid constituents. Although the analgesic effects of Cannabis are attributed to major cannabinoids, evidence indicates other constituents such as minor cannabinoids, terpenes and flavonoids also produce antinociception against animal models of acute, inflammatory, neuropathic, muscle and orofacial pain. In some cases, these constituents produce antinociception that is equivalent or greater compared to that produced by traditional analgesics. Thus, a better understanding of the extent to which these constituents produce antinociception alone in animals is necessary. The purposes of this review are to (1) introduce the different minor cannabinoids, terpenes, and flavonoids found in Cannabis and (2) discuss evidence of their antinociceptive properties in animals.

Suppression of colorectal carcinogenesis by naringin

BACKGROUND

Colorectal cancer is the third most malignant cancer worldwide. Despite novel treatment options, the incidence and mortality rates of colon cancer continue to increase in most countries, especially in US, European and Asian countries. Colorectal carcinogenesis is multifactorial, including dietary and genetic factors, as well as lacking physical activity. Vegetables and fruits contain high amounts of secondary metabolites, which might reduce the risk for colorectal carcinogenesis. Flavonoids are important bioactive polyphenolic compounds. There are more than 4,000 different flavonoids, including flavanones, flavonoids, isoflavonoids, flavones, and catechins in a large variety of plant.

HYPOTHESIS

Among various other flavonoids, naringin in Citrus fruits has been a subject of intense scrutiny for its activity against many types of cancer, including colorectal cancer. We hypothesize that naringin is capable to inhibit the growth of transformed colonocytes and to induce programmed cell death in colon cancer cells.

RESULTS

We comprehensively review the inhibitory effects of naringin on colorectal cancers and address the underlying mechanistic pathways such as NF-κB/IL-6/STAT3, PI3K/AKT/mTOR, apoptosis, NF-κB-COX-2-iNOS, and β-catenin pathways.

CONCLUSION

Naringin suppresses colorectal inflammation and carcinogenesis by various signaling pathways. Randomized clinical trials are needed to determine their effectiveness in combating colorectal cancer.

New Drug Discovery from Medicinal Plants and Phytoconstituents for Depressive Disorders

BACKGROUND & OBJECTIVE

Depression, a risk factor for several serious diseases, is a highly prevalent and life-threatening psychiatric disorder. It can affect the individual's position in life and reduce the living standards. The research on the use of medicinal plants in treating this disease has increased enormously because of the possible low rehabilitation rate and side effects of available synthetic drugs, such as sexual dysfunction, nausea, fatigue, insomnia, hypersomnia, and weight gain.

CONCLUSION

Therefore, this review aimed to draw attention to the antidepressant effects of culinary herbs and traditional medicinal plants and their active components, thereby promoting their use in the development of more potent antidepressants with improved side effect profile.

Natural Flavonoids as Promising Analgesic Candidates: A Systematic Review

Due to the chemical structural diversity and various analgesic mechanisms, an increasing number of studies indicated that some flavonoids from medicinal plants could be promising candidates for new natural analgesic drugs, which attract high interests of advanced users and academic researchers. The aim of this systematic review is to report flavonoids and its derivatives as new analgesic candidates based on the pharmacological evidences. Sixty-four papers were found concerning the potential analgesic activity of 46 flavonoids. In this case, the evidence for analgesic activity of flavonoids and total flavonoids was investigated. Meanwhile, the corresponding analgesic mechanism of flavonoids was discussed by generalizing and analyzing the current publications. Based on this review, the conclusion can be drawn that some flavonoids are promising candidates for painful conditions and deserve particular attention in further research and development.

Differential Effects of Quercetin and Quercetin Glycosides on Human α7 Nicotinic Acetylcholine Receptor-Mediated Ion Currents

Quercetin is a flavonoid usually found in fruits and vegetables. Aside from its antioxidative effects, quercetin, like other flavonoids, has a various neuropharmacological actions. Quercetin-3-O-rhamnoside (Rham1), quercetin-3-O-rutinoside (Rutin), and quercetin-3-(2(G)-rhamnosylrutinoside (Rham2) are mono-, di-, and tri-glycosylated forms of quercetin, respectively. In a previous study, we showed that quercetin can enhance α7 nicotinic acetylcholine receptor (α7 nAChR)-mediated ion currents. However, the role of the carbohydrates attached to quercetin in the regulation of α7 nAChR channel activity has not been determined. In the present study, we investigated the effects of quercetin glycosides on the acetylcholine induced peak inward current (I_ACh) in Xenopus oocytes expressing the α7 nAChR. I_ACh was measured with a two-electrode voltage clamp technique. In oocytes injected with α7 nAChR copy RNA, quercetin enhanced I_ACh, whereas quercetin glycosides inhibited I_ACh. Quercetin glycosides mediated an inhibition of I_ACh, which increased when they were pre-applied and the inhibitory effects were concentration dependent. The order of I_ACh inhibition by quercetin glycosides was Rutin≥Rham1>Rham2. Quercetin glycosides-mediated I_ACh enhancement was not affected by ACh concentration and appeared voltage-independent. Furthermore, quercetin-mediated I_ACh inhibition can be attenuated when quercetin is co-applied with Rham1 and Rutin, indicating that quercetin glycosides could interfere with quercetin-mediated α7 nAChR regulation and that the number of carbohydrates in the quercetin glycoside plays a key role in the interruption of quercetin action. These results show that quercetin and quercetin glycosides regulate the α7 nAChR in a differential manner.

Antiinflammatory, analgesic and antioxidant activities of Cyathula prostrata (Linn.) Blume (Amaranthaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Cyathula prostrata (Linn) Blume (Amaranthaceae) is an annual herb widely used traditionally in the treatment of various inflammatory and pain related health disorders in Nigeria. The aim of this study is to evaluate the anti-inflammatory, analgesic and antioxidant activities of the methanolic extract of Cyathula prostrata (Linn) Blume.

MATERIALS AND METHODS

The anti-inflammatory (phorbol 12-myristate 13-acetate (PMA)-induced reactive oxygen species (ROS), lipopolysaccharide (LPS) induced nitric oxide production in U937 macrophages, LPS-induced COX-2 expression, carrageenan-induced rat paw oedema, arachidonic acid-induced ear oedema and xylene-induced ear oedema), analgesic (acetic acid-induced writhing and hot plate tests) and antioxidant activities (DPPH [1,1-diphenyl-2-picrylhydrazyl] and lipid peroxidation assays) activities of the plant extract were investigated.

RESULTS

The methanolic extract of Cyathula prostrata did not show inhibitory activity in the in vitro PMA-induced reactive oxygen species, LPS-induced nitric oxide production and LPS-induced COX-2 expression assays. In the in vivo anti-inflammatory assays, the extract (50, 100 and 200mg/kg) showed a significant (P<0.05) dose-dependent inhibition in the carrageenan, arachidonic acid and xylene-induced tests. Cyathula prostrata produced a significant (P<0.05, 0.001) dose-dependent inhibition in the acetic acid and hot plate analgesic tests respectively. The plant extract did not exhibit any antioxidant activity in the DPPH and lipid peroxidation assays.

CONCLUSION

The results suggest that the methanolic extract of Cyathula prostrata possesses anti-inflammatory and analgesic activities and this authenticates the use of the plant in the traditional treatment of ailments associated with inflammation and pain.

Antinociceptive, anti-inflammatory effects and acute toxicity of aqueous and ethanolic extracts of Myrtus communis L. Aerial parts in mice

Myrtus communis L. aerial parts have been used in traditional medicine for the treatment of inflammatory disease. In this study 350 mice were divided into three main groups: negative (saline), positive (morphine or diclofenac) controls, and test groups. The acute toxicity was assessed for 2 days. Antinociceptive activity was performed using hot plate and writhing tests. The anti-inflammatory effect was investigated using xylene-induced ear edema and a cotton pellet test. According to phytochemical screening, the extracts contained tannins, alkaloids, and flavonoids. The LD50 values of the aqueous and ethanolic extracts were 0.473 and 0.79 g/kg, respectively. In hot plate test, the aqueous and ethanolic extracts showed significant antinociceptive activity that was inhibited by naloxone. The extracts exhibited antinociceptive activity against acetic acid-induced writhing and also showed significant activity against acute inflammation which was dose dependent for aqueous extract. The ethanolic (0.05 g/kg) and aqueous extracts (0.005, 0.015, and 0.03 g/kg) demonstrated anti-inflammatory effects against chronic inflammation. The aqueous and ethanolic extracts of the aerial parts of M communis L. showed antinociceptive effects and these may be mediated by opioid receptors.

Quercetin Inhibits α3β4 Nicotinic Acetylcholine Receptor-Mediated Ion Currents Expressed in Xenopus Oocytes

Quercetin mainly exists in the skin of colored fruits and vegetables as one of flavonoids. Recent studies show that quercetin, like other flavonoids, has diverse pharmacological actions. However, relatively little is known about quercetin effects in the regulations of ligand-gated ion channels. In the previous reports, we have shown that quercetin regulates subsets of homomeric ligand-gated ion channels such as glycine, 5-HT(3A) and α7 nicotinic acetylcholine receptors. In the present study, we examined quercetin effects on heteromeric neuronal α3β4 nicotinic acetylcholine receptor channel activity expressed in Xenopus oocytes after injection of cRNA encoding bovine neuronal α3 and β4 subunits. Treatment with acetylcholine elicited an inward peak current (I(ACh)) in oocytes expressing α3β4 nicotinic acetylcholine receptor. Co-treatment with quercetin and acetylcholine inhibited I(ACh) in oocytes expressing α3β4 nicotinic acetylcholine receptors. The inhibition of I(ACh) by quercetin was reversible and concentration-dependent. The half-inhibitory concentration (IC(50)) of quercetin was 14.9±0.8 µM in oocytes expressing α3β4 nicotinic acetylcholine receptor. The inhibition of I(ACh) by quercetin was voltage-independent and non-competitive. These results indicate that quercetin might regulate α3β4 nicotinic acetylcholine receptor and this regulation might be one of the pharmacological actions of quercetin in nervous systems.

Quercetin: further investigation of its antinociceptive properties and mechanisms of action

The antinociceptive action of quercetin, a common bioactive flavonoid present in many medicinal plants, was assessed in different models of chemical and thermal nociception in mice. Quercetin (10-60 mg/kg, i.p. or 100-500 mg/kg, p.o.) dose-dependently inhibited nociceptive behavior in the acetic acid-induced pain test. Moreover, quercetin (10-60 mg/kg, i.p.) inhibited both phases of formalin-induced pain, with ID50 values of 374.1 (68.0-402.0) mmol/kg and 103.0 (45.0-201.0) mmol/kg, for the neurogenic and inflammatory phases, respectively. Quercetin (10-60 mg/kg) also inhibited the nociception induced by glutamate and capsaicin by 68.2% and 75.5%, respectively. Its analgesic action was significantly reversed by p-chlorophenylalanine methyl ester, katanserin, methysergide, a GABA(A) antagonist (bicuculline), or a GABA(B) antagonists (baclofen). Its action was also modulated by tachykinins, but was not affected by adrenal-gland hormones. Furthermore, the antinociceptive effects did not result from muscle-relaxant or sedative action. Together, these results indicate that quercetin produces dose-related anti-nociception in several models of chemical pain, through mechanisms that involve interaction with L-arginine-nitric oxide, serotonin, and GABAergic systems. These results confirm and extend other investigations on the analgesic effect of quercetin and its mechanisms of action.

Differential regulations of quercetin and its glycosides on ligand-gated ion channels

Quercetin, one of the flavonoids, is a compound of low molecular weight found in various plants and shows a wide range of diverse neuropharmacological actions. In fruits and vegetables, quercetin exists as monomer- (quercetin-3-O-rhamnoside) (Rham1), dimer- (Rutin), or trimer-glycosides [quercetin-3-(2G-rhamnosylrutinoside)] (Rham2) at carbon-3. In the previous studies, we demonstrated that quercetin inhibits both glycine and 5-hydroxytryptamine type 3, (5-HT3A) receptor channel activities expressed in Xenopus oocytes. However, the effects of quercetin glycosides on glycine and 5-HT3A receptor channel activities are not well known. In the present study, we investigated the effects of quercetin glycosides on the human glycine alpha1 receptor and mouse 5-HT3A receptor channel activities expressed in Xenopus oocytes using a two-electrode voltage clamp technique. In oocytes expressing glycine or 5-HT3A receptors, quercetin- or its glycosides-induced inhibitions on glycine- (IGly) and 5-HT-induced current (I5-HT) were dose-dependent and reversible. Applications of quercetin and its glycosides inhibited IGly in order of quercetin>Rutin> or =Rham1>Rham2. Applications of quercetin and its glycosides inhibited I5-HT in order of Rham2> or =quercetin>Rutin=Rham1. The inhibitions of IGly by quercetin glycosides were non-competitive and voltage-sensitive, whereas the inhibitions of I5-HT by quercetin glycosides were competitive and voltage-insensitive manners. These results also indicate that quercetin glycosides might regulate the human glycine alpha1 and mouse 5-HT3A receptors with differential manners.

Human glycine α1 receptor inhibition by quercetin is abolished or inversed by α267 mutations in transmembrane domain 2

Quercetin, one of the flavonoids, is a compound of low molecular weight found in fruits and vegetables. Besides its antioxidative effect, quercetin also shows a wide range of diverse neuropharmacological actions. However, the cellular mechanisms of quercetin's actions, especially on ligand-gated ion channels and synaptic transmissions, are not well studied. We investigated the effect of quercetin on the human glycine alpha1 receptor channel expressed in Xenopus oocytes using a two-electrode voltage clamp technique. Application of quercetin reversibly inhibited glycine-induced current (I(Gly)). Quercetin's inhibition depends on its dose, with an IC(50) of 21.5+/-.2 microM. The inhibition was sensitive to membrane voltages. Site-directed mutations of S267 to S267Y but not S267A, S267F, S267G, S267K, S267L and S267T at transmembrane domain 2 (TM2) nearly abolished quercetin-induced inhibition of I(Gly). In contrast, in site-directed mutant receptors such as S267 to S267I, S267R and S267V, quercetin enhanced I(Gly) compared to the wild-type receptor. The EC(50) was 22.6+/-1.4, 25.5+/-4.2, and 14.5+/-3.1 microM for S267I, S267R and S267V, respectively. These results indicate that quercetin might regulate the human glycine alpha(1) receptor via interaction with amino acid residue alpha267 and that alpha267 plays a key role in determining the regulatory consequences of the human glycine alpha1 receptor by quercetin.

Quercetin subunit specifically reduces GlyR-mediated current in rat hippocampal neurons

Quercetin is a substance of low molecular weight found in vascular plants with a wide range of biological activities including antioxidative and anti-inflammatory activities. In the present study, the effects of quercetin on native glycine receptors (GlyRs) in cultured rat hippocampal neurons were investigated using a whole-cell patch-clamp technique. Quercetin reversibly and concentration-dependently depressed glycine-induced current (I(Gly)), with an IC50 of 10.7+/-0.24 microM and a Hill coefficient of 1.08+/-0.12. Quercetin depressed maximum I(Gly) and significantly changed the EC50 for glycine and the Hill coefficient. Kinetic analysis indicated that quercetin accelerated the rates of desensitization. Interestingly, after the end of glycine with quercetin coapplication, a transient rebound occurred. The quercetin effects also displayed voltage-dependence, being greater at positive membrane potentials. These effects suggested that quercetin may act as an open channel blocker. Furthermore, in the sequential application protocol, quercetin inhibited the peak amplitude of I(Gly) to a macroscopic degree while slowing GlyR desensitization. These effects implied that quercetin has a depressant effect independent of GlyR channel's opening, which maybe caused by an allosteric mechanism. Strikingly, quercetin inhibited the amplitude of recombinant-induced current mediated by alpha2-, alpha2beta-, alpha3- and alpha3beta-GlyRs but had no effects on alpha1- and alpha1beta-GlyRs that were expressed in HEK293T cells. We also investigated the effects of quercetin on I(Gly) in spinal neurons during development in vitro. The extent of blockade by quercetin on I(Gly) was slighter in spinal neurons than in hippocampal neurons in a development-dependent manner. Taken together, our results suggest that quercetin has possible effects in information processing within a neuronal network by inhibition of I(Gly) and may be useful as a pharmacological probe for identifying the subunit types of GlyRs.

Antinociceptive activity of Syzygium jambos leaves extract on rats

Syzygium jambos (L.) Alston (Myrtaceae) (syn Eugenia jambos) is a widespread medicinal plant traditionally used in sub-Saharan Africa to treat several diseases. The analgesic potential of leaf hydro-alcoholic extracts was assessed in rats. Hot plate and formalin tests were used to estimate cutaneous nociception whereas measurements of forelimb grip force were done to assess muscular nociception under normal and inflammatory conditions. In the hot plate test, Syzygium jambos extract produced a significant increase in the withdrawal response latencies in a dose-dependant manner (10-300 mg/kg i.p.) and with a maximal effect (analgesic efficacy) similar to that of morphine. The extract (100-300 mg/kg i.p.) significantly reduced pain scores in all the phases of the formalin test with an analgesic efficacy higher than that shown by diclofenac. Although the extract (300 mg/kg) did not alter grip force in intact rats, it reversed the reduction in grip force induced by bilateral injection carrageenan in the forelimb triceps. This analgesic effect of the extract on muscle hyperalgesia was not antagonized, but enhanced, by naloxone. Thus, the Syzygium jambos extract has remarkable analgesic effects on both cutaneous and deep muscle pain that is not mediated by opioid receptors.

Role of α2 Receptors in Quercetin-Induced Behavioral Despair in Mice

Depression is a well-defined illness that afflicts a large population worldwide. Various biochemical theories have been described; however, the pathophysiology of depression is still poorly understood. The present study explores the role of a natural flavonoid, quercetin, in the forced swimming model of depression and its interaction with presynaptic alpha(2) adrenoceptors. Quercetin induced a significant behavioral despair, which was abrogated with pretreatment with yohimbine, an alpha(2) adrenoceptor antagonist, and imipramine, a tricyclic antidepressant. The results of the study support the contention that quercetin utilizes presynaptic alpha(2) adrenoceptors in eliciting its depressant activity in mice.

Quercetin as the active principle of Hypericum hircinum exerts a selective inhibitory activity against MAO-A: extraction, biological analysis, and computational study

The methanol extract from Hypericum hircinum leaves exhibited in vitro inhibition of monoamine oxidases (MAO). Bioassay-guided fractionation led to the isolation of quercetin and five compounds identified for the first time from H. hircinum. Quercetin was the only compound with a selective inhibitory activity against MAO-A, with an IC50 value of 0.010 microM. To explain MAO selective inhibition at the molecular level, a computational study was carried out by conformational search and docking techniques using recently determined crystallographic models of both enzymatic isoforms. An in vivo study in mice was carried out using the forced swimming test in order to elucidate the behavioral effects of quercetin.

Participation of alpha2 receptors in the antinociceptive activity of quercetin

The present work was planned to evaluate the antinociceptive activity of quercetin, its site of action, and the involvement of adrenergic receptors in mediating the antinociceptive activity in thermal and chemonociceptive assays. Eight groups were employed in this study: Groups I, II, and III received quercetin alone in different doses, group IV animals were administered clonidine, group V animals were co-administered quercetin and clonidine, group VI animals were administered yohimbine 30 minutes prior to administratin of quercetin, group VII animals were administered yohimbine 30 minutes prior to co-administration of quercetin and clonidine, and group VIII animals were administered 0.5% carboxymethylcellulose in saline (vehicle for quercetin). The thermal nociception was measured by tail flick and hot plate methods. Quercetin produced a significant analgesic effect in a dose-dependent manner. Co-administration of low doses of quercetin and clonidine produced a synergistic analgesic effect. Pretreatment with yohimbine significantly reversed quercetin-as well as clonidine/quercetin combination-induced effects. The results of this study reveal that quercetin induces an antinociceptive effect and that this effect involves primarily the modulation of adrenergic pathways.

Coriandrum sativum: evaluation of its anxiolytic effect in the elevated plus-maze

The clinical applications of benzodiazepines as anxiolytics are limited by their unwanted side effects. Therefore, the development of new pharmacological agents is well justified. Among medicinal plants, Coriandrum sativum L. has been recommended for relief of anxiety and insomnia in Iranian folk medicine. Nevertheless, no pharmacological studies have thus far evaluated its effects on central nervous system. Therefore, the aim of this study was to examine if the aqueous extract of Coriandrum sativum seed has anxiolytic effect in mice. Additionally, its effect on spontaneous activity and neuromuscular coordination were evaluated. The anxiolytic effect of aqueous extract (10, 25, 50, 100 mg/kg, i.p.) was examined in male albino mice using elevated plus-maze as an animal model of anxiety. The effects of the extract on spontaneous activity and neuromuscular coordination were assessed using Animex Activity Meter and rotarod, respectively. In the elevated plus-maze, aqueous extract at 100 mg/kg showed an anxiolytic effect by increasing the time spent on open arms and the percentage of open arm entries, compared to control group. Aqueous extract at 50, 100 and 500 mg/kg significantly reduced spontaneous activity and neuromuscular coordination, compared to control group. These results suggest that the aqueous extract of Coriandrum sativum seed has anxiolytic effect and may have potential sedative and muscle relaxant effects.

Flavonoids with antinociceptive and anti-inflammatory activities from the leaves of Tilia argentea (silver linden)

Silver linden, Tilia argentea Desf. ex DC (Tiliaceae) leaves are used in the treatment of common cold and bronchitis. In order to evaluate this information, antinociceptive and anti-inflammatory activities of the two main flavonoid glycosides: kaempferol-3,7-O-alpha-dirhamnoside and quercetin-3,7-O-alpha-dirhamnoside isolated from the leaves, were investigated. For the antinociceptive activity, p-benzoquinone-induced writhing test and for the anti-inflammatory activity, carrageenan-induced hind paw edema model in mice were used. Both compounds were shown to possess potent antinociceptive and anti-inflammatory activity at 50 mg/kg dose, per os, without inducing any apparent acute toxicity as well as gastric damage.

Antipruritic effects of the fruits of Chaenomeles sinensis

A 35% EtOH extract of the fruits of Chaenomeles sinensis, long utilized as a folk medicine for cough, significantly inhibited the pruritogenic agent compound 48/80 (COM)-induced scratching behavior in mice. Antipruritic activity-guided fractionation and purification yielded active quercetin, apigenin, and catechin derivatives, which exhibited significant inhibitory effects on COM-induced scratching behavior. To the best of our knowledge, apigenin (5), apigenin 7-glucronide (6), and apigenin 4'-methoxy-7-glucronide (acacetin 7-glucronide) (7) were isolated from the fruits of C. sinensis for the first time. The active fraction and these compounds also inhibited serotonin-, platelet activating factor-, and prostaglandin E(2)-induced scratching behavior, but did not inhibit histamine-induced scratching behavior or locomotive behavior. This study also showed that the fruits of C. sinensis could be used to treat allergic itching sensation.

Differential effects of quercetin, a natural polyphenolic flavonoid, on L-type calcium current in pituitary tumor (GH3) cells and neuronal NG108-15 cells

The effects of quercetin, a natural polyphenolic compound, on voltage-dependent L-type Ca(2+) current (I(Ca,L)) in rat pituitary GH(3) cells were investigated with the aid of the whole-cell voltage-camp technique. Quercetin (0.5-200 microM) stimulated I(Ca,L) in a concentration-dependent manner. The current-voltage (I-V) relationship of I(Ca,L) was slightly shifted to more negative potentials in the presence of quercetin. The EC(50) value of the quercetin-induced stimulation of I(Ca,L) was about 7 microM. The presence of quercetin (5 microM) shifted the steady state inactivation curve of I(Ca,L) to a more negative potential by approximately -10 mV. Although quercetin might increase intracellular cyclic AMP, sp-cAMPS did not affect I(Ca,L). In addition, neither flavone nor wortmannin had any effect on the amplitude of I(Ca,L), while epicatechin and genistein slightly suppressed it. Quercetin (50 microM) decreased the amplitude of tetrodotoxin-sensitive Na(+) current in GH(3) cells. Under current-clamp configuration, quercetin could increase the firing frequency of actions potentials. Conversely, in NG108-15 neuronal cells, quercetin suppressed the amplitude of I(Ca,L). The quercetin-induced inhibition of I(Ca,L) was abolished in NG108-15 cells preincubated with t-butyl hydroperoxide (1 mM). Quercetin-mediated stimulation of I(Ca,L) in GH(3) cells was presumably not associated with the level of intracellular cyclic AMP, or with the activity of tyrosine or phosphoinositide 3-kinases. Therefore, the effects of quercetin on ion currents may, at least in part, contribute to the underlying mechanisms through which it affects neuronal or neuroendocrine function.

Flavonoid modulation of ionic currents mediated by GABA(A) and GABA(C) receptors

The modulation of ionotropic gamma-aminobutyric acid (GABA) receptors (GABA-gated Cl(-) channels) by a group of natural and synthetic flavonoids was studied in electrophysiological experiments. Quercetin, apigenin, morine, chrysin and flavone inhibited ionic currents mediated by alpha(1)beta(1)gamma(2s) GABA(A) and rho(1) GABA(C) receptors expressed in Xenopus laevis oocytes in the micromolar range. alpha(1)beta(1)gamma(2s) GABA(A) and rho(1) GABA(C) receptors differ largely in their sensitivity to benzodiazepines, but they were similarly modulated by different flavonoids. Quercetin produced comparable actions on currents mediated by alpha(4)beta(2) neuronal nicotinic acetylcholine, serotonin 5-HT(3A) and glutamate AMPA/kainate receptors. Sedative and anxiolytic flavonoids, like chrysin or apigenin, failed to potentiate but antagonized alpha(1)beta(1)gamma(2s) GABA(A) receptors. Effects of apigenin and quercetin on alpha(1)beta(1)gamma(2s) GABA(A) receptors were insensitive to the benzodiazepine antagonist flumazenil. Results indicate that mechanism/s underlying the modulation of ionotropic GABA receptors by some flavonoids differs from that described for classic benzodiazepine modulation.

Antinociceptive activity ofSempervivum tectorum L. extract in rats

The extract of Sempervivum tectorum L. (Crassulaceae) containing several flavonoids is widely used as an antiinflammatory agent in folk medicine. Previous studies have demonstrated that various flavonoids or flavonoid-containing plant extracts produce significant antinociception, but no data are available concerning their antinociceptive effect especially at the spinal level. The purpose of the present study was to investigate the antinociceptive activity of Sempervivum tectorum L. extract on acute and inflammatory pain sensitivity in awake rats. The pain sensitivity was assessed by the acute tail- flick test in intact rats and by the paw withdrawal test after carrageenan-induced inflammation using heat stimulus. The plant extract was administered intraperitoneally and intrathecally in rats. The intraperitoneal injection of a high dose of the extract (1000 mg/kg) significantly (p < 0.05) increased the paw withdrawal latency of the inflamed paw. The intrathecal administration (30-300 micro g) caused a small, but significant increase (10%-15%) in tail- flick latency. In the carrageenan-induced inflammatory model, the intrathecally applied extract (30-1000 micro g) significantly decreased, but did not relieve the thermal hyperalgesia. The results suggest that the spinal cord does not seem to play an important role in the antinociceptive effects of this plant extract.

Activity of Hypericum brasiliense and Hypericum cordatum on the central nervous system in rodents

Hydroalcoholic extracts from species Hypericum brasiliense Choisy (HB) and Hypericum cordatum (Vell. Conc.) N. Robson (HC), were evaluated on the central nervous system (CNS) in some pharmacological tests. Signs of toxicity were observed for both species during the initial screening when high doses of up to 100 mg/kg (i.p.) and 1000 mg/kg (oral) were utilized. HC presented greater toxicity, with LD(50) of 269 mg/kg, as compared to HB (537 mg/kg). Alterations in sleeping time and in motor coordination were not observed both for HB and for HC. On the other hand, both species showed signs of general depressant action on the CNS, verified by decreased motor activity. Furthermore, animals treated with HB presented an increase in response time to thermal stimulus with doses of 50 mg/kg (i.p.) and 500 mg/kg (oral) suggesting possible analgesic action. Both HB and HC were tested in animal models to verify antidepressant action (forced swimming and hypothermy induced by apomorphine). In these tests, neither of the plants inhibited hypothermy, nor did they reduce immobility time in forced swimming.

Evaluation of the anxiolytic-like effects of Cecropia glazioui Sneth in mice

Cecropia glazioui Sneth has been used in most Latin American countries as an antihypertensive, cardiotonic, and antiasthmatic folk medicine. In the cardiovascular studies to define its antihypertensive action it was noteworthy that animals treated with the aqueous extract (AE) of C. glazioui were much calmer than control animals. That observation prompted the present study, aimed at an investigation of the effects of AE and of two semipurified fractions on mouse behavior as evaluated in the elevated plus-maze test (EPM). Male adult Swiss mice were treated with AE (0.25-1 g/kg po) acutely (1 h) or repeatedly (24, 7, and 1.5 h before the test). After repeated administration of AE, the frequency of entries in the open arms of EPM was increased threefold. A similar profile of action was observed after treatment with the butanolic fraction (Fbut) but not with the aqueous fraction (Faq). These findings suggest that the AE of C. glazioui promotes an anxiolytic-like effect in mice. The active principles responsible for this action are present in the less polar fraction of the extract, the main constituents of which are flavonoids and terpenes, among other compounds.

Effects of quercetin on antioxidant defense in streptozotocin-induced diabetic rats

In light of evidence that some complications of diabetes mellitus may be caused or exacerbated by oxidative damage, we investigated the effects of subacute treatment with the antioxidant quercetin on tissue antioxidant defense systems in streptozotocin-induced diabetic Sprague-Dawley rats (30 days after streptozotocin induction). Quercetin, 2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopyran-4-one, was administered at a dose of 10mg/kg/day, ip for 14 days, after which liver, kidney, brain, and heart were assayed for degree of lipid peroxidation, reduced and oxidized glutathione content, and activities of the free-radical detoxifying enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. Treatment of normal rats with quercetin increased serum AST and increased hepatic concentration of oxidized glutathione. All tissues from diabetic animals exhibited disturbances in antioxidant defense when compared with normal controls. Quercetin treatment of diabetic rats reversed only the diabetic effects on brain oxidized glutathione concentration and on hepatic glutathione peroxidase activity. By contrast, a 20% increase in hepatic lipid peroxidation, a 40% decline in hepatic glutathione concentration, an increase in renal (23%) and cardiac (40%) glutathione peroxidase activities, and a 65% increase in cardiac catalase activity reflect intensified diabetic effects after treatment with quercetin. These results call into question the ability of therapy with the antioxidant quercetin to reverse diabetic oxidative stress in an overall sense.

Analgesic properties of Epilobium angustifolium, evaluated by the hot plate test and the writhing test

The analgesic properties of Epilobium angustifolium (Ea), a plant containing flavonoids with anti-inflammatory activity, have not been sufficiently studied so far. Thus, we decided to evaluate, by the classical hot plate test and the writhing test, the analgesic effect of a dry extract of Ea obtained by evaporating a commercially available mother tincture. In the former assay, the effect of Ea (380 mg/kg) was slightly lower than that of morphine (10 mg/kg s.c.). In the writhing test, which is more sensitive for non-steroidal analgesics, the effect of Ea was already significant (P < 0.05) at 95 mg/kg while at doses > or = 190 mg/kg, its activity was similar to that of lysine acetylsalicylate (300 mg/kg). The LD50 of this dry extract of Ea was 1.4+/-0.1 g/kg. Further studies are necessary for the identification of the active principles and the elucidation of their mechanism of action.

Sedative activity of two flavonol glycosides isolated from the flowers of Albizzia julibrissin Durazz

The flowers of Albizzia julibrissin are used as a sedative in oriental traditional medicine. The phytochemical study of this plant allowed the isolation of two flavonol glycosides, quercitrin (1) and isoquercitrin (2). The sedative activity of these compounds was evaluated, and both compounds 1 and 2 increased pentobarbital-induced sleeping time in dose-dependent manner in mice. These results support the use of the flowers of this plant as a sedative agent.

A comparative study of the effects of sparteine, lupanine and lupin extract on the central nervous system of the mouse

Lupin is toxic because of its alkaloid content, sparteine and lupanine in particular. Although the pharmacological properties of sparteine are well known those of lupanine have not been much studied. This paper reports procedures for extraction, purification and crystallization of lupanine, and methods for the preparation of an extract for injection of Lupinus mutabilis Sweet, and for the determination of the acute toxicity and maximum non-lethal dose (DL0) of lupanine, sparteine and lupin extract in the mouse. The three substances were tested on the central nervous system (CNS) for locomotor activity, for interaction with specific drugs used for treatment of the CNS (the stimulant drugs amphetamine and pentetrazol and the depressant drugs pentobarbital and chlorpromazine) and for analgesic activity. The results indicate that lupanine and lupin extract are less toxic than sparteine and that at the doses studied the three products have a weak sedative effect on the CNS.

Overview--flavonoids: a new family of benzodiazepine receptor ligands

Benzodiazepines (BDZs) are the most widely prescribed class of psychoactive drugs in current therapeutic use, despite the important unwanted side-effects that they produce such as sedation, myorelaxation, ataxia, amnesia, ethanol and barbiturate potentiation and tolerance. Searching for safer BDZ-receptor (BDZ-R) ligands we have recently demonstrated the existence of a new family of ligands which have a flavonoid structure. First isolated from plants used as tranquilizers in folkloric medicine, some natural flavonoids have shown to possess a selective and relatively mild affinity for BDZ-Rs and a pharmacological profile compatible with a partial agonistic action. In a logical extension of this discovery various synthetic derivatives of those compounds, such as 6,3'-dinitroflavone were found to have a very potent anxiolytic effect not associated with myorelaxant, amnestic or sedative actions. This dinitro compound, in particular, exhibits a high affinity for the BDZ-Rs (Ki = 12-30 nM). Due to their selective pharmacological profile and low intrinsic efficacy at the BDZ-Rs, flavonoid derivatives, such as those described, could represent an improved therapeutic tool in the treatment of anxiety. In addition, several flavone derivatives may provide important leads for the development of potent and selective BDZ-Rs ligands.

Short-term treatment of Paget's disease of bone with ipriflavone

Ipriflavone (IP), an isoflavone derivative, seems to prevent the loss of bone mass through the inhibition of bone resorption, mainly inhibiting the recruitment of osteoclasts. We investigated whether a brief course of treatment with IP can reduce biochemical parameters of accelerated bone turnover and bone pain in patients with active Paget's disease of bone. Sixteen patients (9 males and 7 females) with active Paget's disease were randomly allocated to two different crossed-over dose regimens of treatment with IP (600 mg/day vs. 1200 mg/day). Each treatment course lasted 30 days and the wash-out period between the two sequences was 15 days. Serum alkaline phosphatase (Al.Ph.) and urinary hydroxyproline/creatinine excretion (HOP/Cr) were reduced after each sequence. At the end of the 600/1200 mg/day treatment sequence, serum Al.Ph. and HOP/Cr decreased with 32% and 25.6% respectively. At the end of the 1200/600 mg/day treatment sequence, serum Al.Ph. and HOP/Cr decreased with 33% (P < 0.01) and 24.1% (P < 0.05) respectively. Furthermore, a significant decrease in bone pain was observed during the 1200/600 mg/day sequence (P < 0.01). Both treatment schedules were well tolerated and the patients' compliance resulted excellent. Our results indicate that short-term treatment with IP can reduce biochemical parameters of disease activity and bone pain in patients with active Paget's disease of bone.