The search of potential inhibitors of the AcrAB-TolC system of multidrug-resistant Escherichia coli: an in silico approach.

The number of infections caused by multidrug antibiotic resistance (MDR) species is increasing globally. The efflux pump system, AcrAB-TolC, confers Escherichia coli resistance to many antibiotics and results in poor treatment outcomes. Different rational drug design techniques were employed to search for a safe and effective AcrAB-TolC system inhibitor. Ligand docking was performed to analyze the binding of different ArcB substrates and/or inhibitors in the different AcrAB crystal structure binding sites. The validated docking site using the established docking preferences was used to perform virtual high-throughput screening on a large library of compounds. Domperidone, a known and safe over-the-counter antiemetic drug, was proposed as an effective ArcB inhibitor. Microbiological studies confirmed the computational results and domperidone reversed the resistance to the antibiotics: levofloxacin and ciprofloxacin in the MDR E. coli stains with an effect that surpassed the effect of the known efflux pump inhibitor, reserpine. In addition, it was able to increase both antibiotic effects on susceptible strains. This finding suggests that the antibiotic-domperidone combination can be used clinically to treat infections caused by multidrug-resistant E. coli strains.

Antidepressant, Anxiolytic and Antinociceptive Activities of Constituents from Rosmarinus Officinalis.

PURPOSE: Rosmarinus officinalis, traditionally known as rosemary, has been widely used in traditional medicines and has long been known as the herb of remembrance. However, few studies have investigated the effects of non-volatile components of rosemary on central nervous system function. METHODS: Fractionation of R. officinalis led to the isolation of salvigenin, rosmanol and cirsimaritin, which were investigated in mouse models of acute toxicity, antinociception (tail immersion and hot plate tests), depression (tail suspension and forced swim tests) and anxiety (elevated plus maze and light/dark box paradigms). RESULTS: Rosmanol, cirsimaritin and salvigenin were not found to exhibit any signs of acute toxicity (50-200 mg/kg), but elicited antinociceptive, antidepressant and anxiolytic activities. CONCLUSION: Rosmanol, cirsimaritin and salvigenin, all previously shown to have biphasic modulation of GABAA receptors, demonstrated CNS activity in mouse models of antinociception, antidepressant and anxiolysis. The anxiolytic activity of all three compounds was not ameliorated by flumazenil, but was inhibited by pentylenetetrazol, suggesting a mode of action via GABAA receptors at a site other than the high affinity benzodiazepine binding site. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Stigmasterol can be new steroidal drug for neurological disorders: Evidence of the GABAergic mechanism via receptor modulation.

BACKGROUND: Gamma-aminobutyric acid A (GABAA) receptors have been implicated in anxiety and epileptic disorders. HYPOTHESIS/PURPOSE: This study aimed to investigate the effects of stigmasterol, a plant sterol (phytosterol) isolated from Artemisia indica Linn on neurological disorders. METHODS: Stigmasterol was evaluated on various recombinant GABAA receptor subtypes expressed in Xenopus laevis oocytes and its anxiolytic and anticonvulsant potential was assessed using the elevated plus maze (EPM), light-dark box (LDB) test, and pentylenetetrazole- (PTZ-) induced seizure paradigms. Furthermore, computational modeling of α2ß2γ2L, α4ß3δ, and α4ß3 subtypes was performed to gain insights into the GABAergic mechanism of stigmasterol. For the first time, a model of GABAδ subtype was generated. Stigmasterol was targeted to all the binding sites (neurotransmitters, positive and negative modulator binding sites) of GABAA α2ß2γ2L, α4ß3, and α4ß3δ complexes by in silico docking. RESULTS: Stigmasterol enhanced GABA-induced currents at ternary α2ß2γ2L, α4ß3δ, and binary α4ß3 GABAAR subtypes. The potentiation of GABA-induced currents at extrasynaptic α4ß3δ was significantly higher compared to the binary α4ß3 subtype, indicating that the δ subunit is important for efficacy. Stigmasterol was found to be a potent positive modulator of the extrasynaptic α4ß3δ subtype, which was also confirmed by computational analysis. The computational analysis reveals that stigmasterol preferentially binds at the transmembrane region shared by positive modulators or a binding site constituted by the M2-M3 region of α4 and M1-M2 of ß3 at α4ß3δ complex. In in vivo studies, Stigmasterol (0.5-3.0 mg/kg, i.p.) exerted significant anxiolytic and anticonvulsant effects in an identical manner of allopregnanolone, indicating the involvement of a GABAergic mechanism. CONCLUSION: To our knowledge, this is the first study reporting the positive modulation of GABAA receptors, anxiolytic and anticonvulsant potential of stigmasterol. Thus, stigmasterol is considered to be a candidate steroidal drug for the treatment of neurological disorders due to its positive modulation of GABA receptors.

Involvement of selective GABA-A receptor subtypes in amelioration of cisplatin-induced neuropathic pain by 2'-chloro-6-methyl flavone (2'-Cl-6MF).

Cisplatin-induced peripheral neuropathic pain is a common adverse effect of chemotherapy. The present study evaluated the effects of 2'-chloro-6-methylflavone (2'-Cl-6MF) at recombinant α1ß2γ2L, α2ß1-3γ2L, and α3ß1-3γ2L GABA-A receptor subtypes expressed in Xenopus oocytes and subsequently evaluated its effectiveness in cisplatin-induced neuropathic pain. The results showed that 2'-Cl-6MF potentiated GABA-elicited currents at α2ß2/3γ2L and α3ß2/3γ2L GABA-A receptor subtypes. The potentiation was blocked by the co-application of flumazenil (a benzodiazepine (BDZs) site antagonist). In behavioral studies, mechanical allodynia was induced by intraplantar injection of cisplatin (40 µg/paw) in Sprague Dawley rats, and behavioral assessments were made 24 h after injection. 2'-Cl-6MF (1, 10, 30, and 100 mg/kg, i.p.), was administered 1 h before behavioral evaluation. Administration of 2'-Cl-6MF (30 and 100 mg/kg, i.p) significantly enhanced the paw withdrawal threshold and decreased mechanical allodynia. The standard drugs, gabapentin (GBP) at the dose of 70 mg/kg, and HZ 166 (16 mg/kg), i.p. also significantly enhanced the paw withdrawal threshold in mechanical allodynia. Pretreatment with pentylenetetrazole (PTZ) (15 mg/kg, i.p.) and flumazenil reversed the antinociceptive effect of 2'-Cl-6MF in mechanical allodynia indicating GABAergic mechanisms. Moreover, the binding mechanism of 2'-Cl-6MF was rationalized by in silico modeling tools. The 3D-coordinates of α2ß2γ2L and α2ß3γ2L were generated after homology modeling of the α2 subtype and 2'-Cl-6MF was at predicted binding sites of the developed models. The α2 model was compared with the α1 and α3 subunits via structural and sequence alignment. Molecular docking depicted that the compound binds efficiently at the neuromodulator binding site of the receptors. The findings of this study revealed that 2'-Cl-6MF ameliorated the manifestations of cisplatin-induced neuropathic pain in rats. Furthermore, we also conclude that GABAergic mechanisms may contribute to the antinociceptive effect of 2'-Cl-6MF. The molecular docking studies also confirm the involvement of the BDZs site of GABA-A receptors. It was observed that Ile230 of α2 stabilize the chlorophenyl ring of 2'-Cl-6MF through hydrophobic interactions, which is replaced by Val203 in α1 subunit. However, the smaller side chain of Val203 does not provide hydrophobic interaction to the compound due to high conformational flexibility of α1 subunit.

Antidepressant potential of novel flavonoids derivatives from sweet violet (Viola odorata L): Pharmacological, biochemical and computational evidences for possible involvement of serotonergic mechanism.

Plant-derived natural constituents are of great interest in modern drug discovery due to their natural diversity. Viola odorata L has been traditionally used for the treatment of neuropsychiatric disorders. The present study was undertaken to isolate phytoconstituents including three flavonoids 5,7-Dihydroxy-3,6-dimethoxyflavone[1] 5,7,4'-trihydroxy-3',5'dimethoxyflavone [2] and 5,7,4'-trihydroxy-3'-methoxyflavone [3] from the whole plant of Viola odorata L and to investigate the antidepressant-like effects of these compounds and their possible mechanism of action using antagonists of the serotonergic, dopaminergic and adrenergic system. Classical animal models of depression including tail suspension test (TST) and forced swimming test (FST) using mice were used to evaluate the antidepressant-like effects. Mice were divided into various groups and were administered with either vehicle control, fluoxetine (FLX), or test compounds 1-3 intraperitoneally (i.p.). For experiments involving mechanism determination, mice were pretreated with 5-HT, dopamine and adrenergic antagonists. The brain 5-HT levels were determined following FST. Molecular docking studies were carried out to determine the binding affinity of compounds 1-3 to serotonergic receptors. The results indicated that compounds 1-3 at the dose of 1-30 mg/kg, i.p significantly decreased the immobility time in the FST and TST in mice. The reduction in immobility time was reversed by pre-treating the mice with pCPA (5-HT synthesis inhibitor) 100 mg/kg, i.p. and 5-HT receptor antagonists including WAY100635 (5-HT1a antagonist), ketanserin (a 5-HT2a antagonist) and ondansetron (5-HT3 antagonist) but not with prazosin (α1-adrenergic antagonist) and SCH23390 (D1 dopaminergic antagonist) or haloperidol (D2 dopaminergic antagonist). Moreover, in neurochemical assays, compounds 1-3 caused a significant increase in the 5-HT level in the brain tissue as compared to vehicle. These increases were reversed in the mice groups pretreated with pCPA. Furthermore, molecular docking results also depict that compounds 1-3 can interact with 5HT1A, 5HT2A, and 5HT3 receptors, and are more specific to the 5HT3 receptor subtype. In conclusion, the findings of this study clearly suggest that compounds 1-3 possess antidepressant-like effects which might be mediated via the serotonergic system.

Medicinal Plants Used by Traditional Healers in Jordan, the Tafila Region.

BACKGROUND: The reporting of the medicinal plants and their traditional uses is important in order to prevent this knowledge from being lost. The aims of this study were to collect information concerning the traditional use of medicinal plants in the region of Tafila; identify the most important medicinal plants; determine the relative importance of the species surveyed; and calculate the informant consensus factor (Fic) in relation to medicinal plant use. MATERIALS AND METHODS: Data on the traditional medicinal uses of local plants were collected using qualitative tools. The informant consensus factor (Fic) for the category of aliments and the use value (UV) of the plant species were calculated. RESULTS AND CONCLUSIONS: The survey revealed that 41 plant species are still in use in Tafila for the treatments of various diseases. Problems of the digestive system had the highest Fic values, while Allium cepa L. and Matricaria aurea (Loefl.) Sch. Bip. scored the highest UV. SUMMARY: The medicinal plants used by local people of the Tafila area of Jordan their traditional uses were investigated. forty one plant species are still in use in Tafila for the traditional treatment of various diseases. The preservation of this knowledge is important not only for maintaining cultural and traditional resources but also as a resource for the future identification of leads for drug development. The use of Fic and the UV to identify plant species that are consistently used in the treatment of specific ailments assists in narrowing down the search for new effective plant-derived medicines and in validating the use of traditional medicines. Data on the traditional medicinal uses of local plants was collected using qualitative tools. The informant consensus factor (Fic) for category of aliments and the use value (UV) of the plant species were calculated. in the Tafila region, the Fic values are relatively low, indicating a low level of shared knowledge and that a number of different species are used to treat similar disorders. This may be a result of the great diversity of vegetation types found across the Tafila region, with the specific plant chosen being dependent on the species most readily available in the different vegetation zones. Interestingly, however, the UVs calculated for a number of species in the Tafila region are relatively high, compared with those recorded in other areas of Jordan. These high UVs indicate that despite the diversity of vegetation types across the Tafila region, a number of plants are highly valued for medicinal use throughout the whole region. This study contributes to the body of knowledge about the use of plants in traditional medicine, helping to document and maintain the knowledge that has been traditionally passed directly from person to person. The preservation of this knowledge is important not only for maintaining cultural and traditional resources but also as a resource for the future identification of leads for drug development. Problems of the digestive system had the highest Fic values, while Allium cepa L. and Matricaria aurea (Loefl.) Sch. Bip. scored the highest UV. Comparison with other ethnopharmacological studies in the region found consensus about many of the uses reported, and also identified localized uses of some species. Experimental evidence from the literature offered support for many of the reported uses. Abbreviations used: Fic: Informants consensus factor, nur: number of use reports per each category, nt: number of taxa used, UV: use value of a species, U: number of uses per species, n: number of informants.

Molecular docking and antiamnesic effects of nepitrin isolated from Rosmarinus officinalis on scopolamine-induced memory impairment in mice.

Rosmarinus officinalis has long been known as the herb of remembrance. The present study was undertaken to investigate the anti-amnesic effects of nepitrin isolated from Rosmarinus officinalis using in-vivo models of Y-maze and novel object recognition test (NORT) along with in vitro antioxidant and acetylcholinesterase (AChE) and buterylcholinesterase (BuChE) inhibition potential. Nepitrin showed a concentration dependent inhibition of AChE and BuChE enzymes with IC50 values of 65 and 72µg/mL, respectively and antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) with IC50 values 270 and 210µg/mL, respectively. In mice, nepitrin reversed the amnesia induced by scopolamine as indicated by a dose-dependent increase in spontaneous alternation performance in the Y-maze task (p <0.05 versus scopolamine) and increase in the discrimination index in the novel object recognition test (NORT) comparable to the standard drug donepezil 2mg/kg. Molecular docking studies were performed and the GlideScore of nepitrin was consistent with its experimental AChE inhibitory activities. Nepitrin occupied the same binding site forming similar interactions to those formed by donepezil in the crystal structure. Thus, nepitrin could provide a lead for the development of therapeutic agent useful in cognition and memory disorders such as Alzheimer's disease.

GABA-A Receptor Modulation and Anticonvulsant, Anxiolytic, and Antidepressant Activities of Constituents from Artemisia indica Linn.

Artemisia indica, also known as "Mugwort," has been widely used in traditional medicines. However, few studies have investigated the effects of nonvolatile components of Artemisia indica on central nervous system's function. Fractionation of Artemisia indica led to the isolation of carnosol, ursolic acid, and oleanolic acid which were evaluated for their effects on GABA-A receptors in electrophysiological studies in Xenopus oocytes and were subsequently investigated in mouse models of acute toxicity, convulsions (pentylenetetrazole induced seizures), depression (tail suspension and forced swim tests), and anxiety (elevated plus maze and light/dark box paradigms). Carnosol, ursolic acid, and oleanolic acid were found to be positive modulators of α1ß2γ2L GABA-A receptors and the modulation was antagonized by flumazenil. Carnosol, ursolic acid, and oleanolic acid were found to be devoid of any signs of acute toxicity (50-200 mg/kg) but elicited anticonvulsant, antidepressant, and anxiolytic activities. Thus carnosol, ursolic acid, and oleanolic acid demonstrated CNS activity in mouse models of anticonvulsant, antidepressant, and anxiolysis. The anxiolytic activity of all three compounds was ameliorated by flumazenil suggesting a mode of action via the benzodiazepine binding site of GABA-A receptors.