Antidepressant-like effect of riparin II fromAniba ripariain mice: evidence for the involvement of the monoaminergic system

Antidepressant-like effect of riparin I and riparin II against CUMS-induced neuroinflammation via astrocytes and microglia modulation in mice

Depression is a common mood disorder and many patients do not respond to conventional pharmacotherapy or experience a variety of adverse effects. This work proposed that riparin I (RIP I) and riparin II (RIP II) present neuroprotective effects through modulation of astrocytes and microglia, resulting in the reversal of depressive-like behaviors. To verify our hypothesis and clarify the pathways underlying the effect of RIP I and RIP II on neuroinflammation, we used the chronic unpredictable mild stress (CUMS) depression model in mice. Male Swiss mice were exposed to stressors for 28 days. From 15 th to the 22 nd day, the animals received RIP I or RIP II (50 mg/kg) or fluoxetine (FLU, 10 mg/kg) or vehicle, by gavage. On the 29 th day, behavioral tests were performed. Expressions of microglia (ionized calcium-binding adaptor molecule-1 - Iba-1) and astrocyte (glial fibrillary acidic protein - GFAP) markers and levels of cytokines tumor necrosis factor alfa (TNF-α) and interleukin 1 beta (IL-1β) were measured in the hippocampus. CUMS induced depressive-like behaviors and cognitive impairment, high TNF-α and IL-1β levels, decreased GFAP, and increased Iba-1 expressions. RIP I and RIP II reversed these alterations. These results contribute to the understanding the mechanisms underlying the antidepressant effect of RIP I and RIP II, which may be related to neuroinflammatory suppression.

New insights about the antidepressant-like effects of riparin A in a chronic murine model of depression

Riparin A is a synthetic form of natural riparins. Acute scale studies that take into consideration the structure-activity relationship have shown preliminary evidence of antidepressant and anxiolytic effects of riparin A, similar to that already known for other riparins. However, for better pharmacological characterization of this new compound, further studies are required. The aim of this work was to evaluate the effect of chronic treatment with riparin A (10 mg/kg; intraperitoneally) on depressive-like behavior in the forced swimming test and tail suspension test, as well as the reduction of anhedonia in the sucrose preference test, and on anxiety-like behavior in the open field and elevated plus maze apparatus, triggered in rats previously subjected to unpredictable chronic mild stress by 4 weeks. In addition, a pentobarbital-induced sleep time test was also used. Riparin A reduced the duration of immobility in both the forced swimming test and tail suspension test, as well as attenuated the anhedonia in the sucrose preference test. Furthermore, riparin A appears to produce anxiolytic effects in rats exposed to an open field and elevated plus maze, while increasing the alertness/vigilance in rats submitted to pentobarbital-induced sleep time test, without altering their locomotor integrity. Our results suggest that chronic riparin A appears to be a potential pharmacological target for new studies on the control of depression- and anxiety-like behaviors in stressed rats.

Riparin II-type benzamides as novel antibiofilm agents against dermatophytes: chemical synthesis, in vitro, ex vivo and in silico evaluation

BACKGROUND

The ability of dermatophytes to develop biofilms in host tissues confers physical and biochemical resistance to antifungal drugs. Therefore, research to find new compounds against dermatophyte biofilm is crucial.

OBJECTIVES

To evaluate the antifungal activity of riparin II (RIP2), nor-riparin II (NOR2) and dinor-riparin II (DINOR2) against Trichophyton rubrum, Microsporum canis and Nannizzia gypsea strains.

METHODS

Initially, we determined the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of benzamides. We evaluated the inhibitory effects on the development of dermatophyte biofilms using in vitro and ex vivo models. Finally, we built three-dimensional models of the sulphite pump Ssu1 to investigate the interactions with the benzamides by molecular docking.

RESULTS

RIP2 showed a broad spectrum of activity against T. rubrum, M. canis and N. gypsea, whereas NOR2 and DINOR2 were more selective. Furthermore, the shortening of the carbon chain from RIP2 benzamide to NOR2 and DINOR2 homologs caused a decrease in the MIC values. The benzamides reduced biofilm production and viability in vitro (P < 0.05) at MIC. This result was similar ex vivo in human nail fragments tests, but NOR2 and DINOR2 showed significant results at 2xMIC (P < 0.05). We constructed a model of the Ssu1 protein for each dermatophyte with high similarity. Molecular docking showed that the benzamides obtained higher binding energy values than ciclopirox.

CONCLUSIONS

Our study shows the antibiofilm potential for riparin II-type benzamides as new drugs targeting dermatophytes by inhibiting the Ssu1 protein.

Involvement of Anti-Inflammatory and Stress Oxidative Markers in the Antidepressant-like Activity of Aloysia citriodora and Verbascoside on Mice with Bacterial Lipopolysaccharide- (LPS-) Induced Depression

Aloysia citriodora Palau is popularly used to treat nervous disorders. Experimental evidence has indicated that verbascoside (VBS) isolated from A. citriodora has pharmacological potential. In this study, we evaluated the antidepressant-like effects of a hydroalcoholic extract of A. citriodora (HEAc) and VBS against lipopolysaccharide- (LPS-) induced depressive-like behavior in mice. In the pretreatment protocol (performed to evaluate the preventive potential), mice were pretreated with HEAc (3, 30, or 300 mg/kg) or VBS (30 mg/kg) before the administration of LPS. In the posttreatment protocol (performed to evaluate the therapeutic potential), mice were initially administered LPS and were subsequently given HEAc (3, 30, or 300 mg/kg) or VBS (30 mg/kg). In both treatments, the mice were submitted to an open-field test and tail suspension test (TST) at 6 and 24 h after LPS administration. The posttreatment evaluation revealed that HEAc (30 or 300 mg/kg) and VBS produced an antidepressant-like effect, as indicated by a reduction in the time spent with no movement in the TST. Moreover, HEAc (30 or 300 mg/kg) was found to reduce interleukin-6 (IL-6) levels and N-acetyl-glycosaminidase activity in the hippocampus, increase glutathione (GSH) levels in the hippocampus and cortex, and enhance IL-10 in the cortex and, at a dose of 300 mg/kg, reduced myeloperoxidase activity in the cortex. Contrastingly, no comparable effects were detected in mice subjected to the pretreatment protocol. Administration of VBS similarly reduced the levels of IL-6 in the hippocampus and increased GSH levels in the cortex. Our observations indicate that both HEAc and VBS show promising antidepressant-like potential, which could be attributed to their beneficial effects in reducing neuroinflammatory processes and antioxidant effects in the central nervous system.

Translational Informatics for Natural Products as Antidepressant Agents

Depression, a neurological disorder, is a universally common and debilitating illness where social and economic issues could also become one of its etiologic factors. From a global perspective, it is the fourth leading cause of long-term disability in human beings. For centuries, natural products have proven their true potential to combat various diseases and disorders, including depression and its associated ailments. Translational informatics applies informatics models at molecular, imaging, individual, and population levels to promote the translation of basic research to clinical applications. The present review summarizes natural-antidepressant-based translational informatics studies and addresses challenges and opportunities for future research in the field.

Antidepressant activity of Riparin A in murine model

Depression and anxiety are common neuropsychiatric disorders that usually appear as comorbidities. The development of new drugs is crucial for safer and more effective clinical management of both disorders. Riparin A is a synthetic chemical analog of riparins that naturally occur in several medicinal plants. Marked pharmacological effects such as anxiolytic and antidepressant properties characterize this class of compounds. However, little is known about the potential anxiolytic and antidepressant effects of Riparin A. In this work, we showed that, unlike other riparins, Riparin A exerts only a very mild anxiolytic-like effect as demonstrated by the results of classical behavioral tests such as the elevated plus-maze, light-dark box and open-field tests in rats. However, all doses of Riparin A (2.5; 5.0 and 10 mg/kg; intraperitoneal) have shown significant antidepressant activity in rats submitted to forced swimming test. In addition to this interesting pharmacological property, Riparin A did not promote any important alterations in the locomotor performance of the animals as specifically demonstrated by the rotarod test. Furthermore, Riparin A did not induce sedation in treated animals; instead, this compound appears to increase the animal's state of alertness as measured by the latency time to loss of reflexes and time to recovery from sleep in rats submitted to the pentobarbital-induced sleep time test. The present results point to an antidepressant effect of Riparin A and reinforce the pharmaceutical interest in the group of riparins, particularly their high potential for use in new studies investigating the structure-activity relationships between member compounds.

Medicinal Plants in the Treatment of Depression: Evidence from Preclinical Studies

Medicinal plants and their extracts are natural remedies with enormous potential for treating various diseases, including depression and anxiety. In the case of depression, hundreds of plants have traditionally been used in folk medicine for generations. Different plant extracts and natural products have been analyzed as potential antidepressant agents with validated models to test for antidepressant-like effects in animals, although other complementary studies have also been employed. Most of these studies focus on the possible mediators implicated in these potential effects, with dopamine, serotonin, and noradrenaline being the principal neurotransmitters implicated, both through interference with receptors and with their metabolism by monoamino oxidases, as well as through neuro-endocrine and neuroprotective effects. There are approximately 650 reports of antidepressant-like medicinal plants in PubMed; 155 of them have been compiled in this review, with a relevant group yielding positive results. Saffron and turmeric are the most relevant species studied in both preclinical and clinical studies; St. John's wort or kava have also been tested extensively. To the best of our knowledge, no review to date has provided a comprehensive understanding of the biomolecular mechanisms of action of these herbs or of whether their potential effects could have real benefits. The purpose of this narrative review is to provide an update regarding medicinal plants from the year 2000 to the present to examine the therapeutic potential of these antidepressant-like plants in order to contribute to the development of new therapeutic methods to alleviate the tremendous burden that depression causes worldwide.

Psychopharmacological effects of riparin III from Aniba riparia (Nees) Mez. (Lauraceae) supported by metabolic approach and multivariate data analysis

Background

Currently there is a high prevalence of humor disorders such as anxiety and depression throughout the world, especially concerning advanced age patients. Aniba riparia (Nees) Mez. (Lauraceae), popular known as “louro”, can be found from the Amazon through Guianas until the Andes. Previous studies have already reported the isolation of alkamide-type alkaloids such as riparin III (O-methyl-N-2,6-dyhydroxy-benzoyl tyramine) which has demonstrated anxiolytic and antidepressant-like effects in high doses by intraperitoneal administration.

Methods

Experimental protocol was conducted in order to analyze the anxiolytic-like effect of riparin III at lower doses by intravenous administration to Wistar rats (Rattus norvegicus) (n = 5). The experimental approach was designed to last 15 days, divided in 3 distinct periods of five days: control, anxiogenic and treatment periods. The anxiolytic-like effect was evaluated by experimental behavior tests such as open field and elevated plus-maze test, combined with urine metabolic footprint analysis. The urine was collected daily and analyzed by ¹H NMR. Generated data were statistically treated by Principal Component Analysis in order to detect patterns among the distinct periods evaluated as well as biomarkers responsible for its distinction.

Results

It was observed on treatment group that cortisol, biomarker related to physiological stress was reduced, indicating anxiolytic-like effect of riparin III, probably through activation of 5-HT_2A receptors, which was corroborated by behavioral tests.

Conclusion

¹H NMR urine metabolic footprint combined with multivariate data analysis have demonstrated to be an important diagnostic tool to prove the anxiolytic-like effect of riparin III in a more efficient and pragmatic way.

Involvement of monoaminergic targets in the antidepressant- and anxiolytic-like effects of the synthetic alkamide riparin IV: Elucidation of further mechanisms through pharmacological, neurochemistry and computational approaches

Despite recent advances, current antidepressants have considerable limitations: late onset of action and the high profile of refractoriness. Biomedical research with natural products has gained growing interest in the last years, and had provide useful candidates for new antidepressants. Riparins are a group of natural alkamides obtained from Aniba riparia, which had marked neuroactive effects, mainly as antidepressant and antinociceptive agents. We made modifications of the basic structure of riparins, originating a synthetic alkamide, also known as riparin IV (RipIV). RipIV demonstrated a superior analgesic effect than its congeners and a marked antidepressant-like effect. However, the basic mechanism for the central effects of RipIV remains unknown. Here, we aimed to investigate the participation of monoaminergic neurotransmission targets in the antidepressant-like effects of RipIV. To do this, we applied a combined approach of experimental (classical pharmacology and neurochemistry) and computer-aided techniques. Our results demonstrated that RipIV presented antidepressant- and anxiolytic-like effects without modifying locomotion and motor coordination of mice. Also, RipIV increased brain monoamines and their metabolite levels. At the higher dose (100 mg/kg), RipIV increased serotonin concentrations in all studied brain areas, while at the lower one (50 mg/kg), it increased mainly dopamine and noradrenaline levels. When tested with selective receptor antagonists, RipIV antidepressant effect showed dependence of the activation of multiple targets, including D1 and D2 dopamine receptors, 5-HT2A/2, 5-HT3 receptors and α2 adrenergic receptors. Molecular docking demonstrated favorable binding conformation and affinity of RipIV to monoamine oxidase B (MAO-B), serotonin transporter (SERT), α1 receptor, D2 receptor, dopamine transporter (DAT) and at some extent GABA-A receptor. RipIV also presented a computationally predicted favorable pharmacokinetic profile. Therefore, this study demonstrated the involvement of monoaminergic targets in the mechanism of RipIV antidepressant-like action, and provide evidence of it as a promising new antidepressant.

Polymorphism in natural alkamides from Aniba riparia (Nees) Mez (Lauraceae)

The elucidation of crystal structures of polymorphs of riparins I, II, and III combined with thermal analysis studies allowed the determination of the thermodynamic relationships between polymorphic pairs.

The Acute and Chronic Cognitive and Cerebral Blood-Flow Effects of Nepalese Pepper (Zanthoxylum armatum DC.) Extract-A Randomized, Double-Blind, Placebo-Controlled Study in Healthy Humans

Background: Zanthoxylum armatum DC. (ZA) is a traditional Asian culinary spice and medicinal compound, which is rich in monoterpenes and hydroxy α-sanshool. Mechanistic interactions with the monoamine, cholinergic and cannabinoid neurotransmission systems, as well as transient receptor potential (TRP) and potassium ion channels, may predispose ZA to modulate human brain function. Objectives: To investigate the effects of a single dose and 56-days supplementation with a lipid extract of ZA on cognitive function, mood and cerebral blood-flow (CBF) parameters in the pre-frontal cortex during cognitive task performance. Design: Double-blind, randomized, parallel groups study with N = 82 healthy males and females between the ages of 30 and 55 years. Assessments were undertaken pre-dose and at 1, 3 and 5 hours post-dose on the first (Day 1) and last (Day 56) days of supplementation. Results: A single dose of ZA (Day 1) resulted in acute improvements on a 'Speed of Attention' factor and the Rapid Visual Information Processing (RVIP) task, in comparison to placebo. However, following ZA participants were less accurate on the name-to-face recall task. After 56 days of ZA consumption (Day 56), speed was enhanced on a global 'Speed of Performance' measure, comprising data from all of the timed tasks in the computerized battery. Participants also completed more correct Serial 3s Subtractions at the 3 hours assessment and were less mentally fatigued throughout the day than participants consuming placebo. These effects were complemented on both Day 1 and Day 56 by modulation of CBF parameters, as assessed by Near Infrared Spectroscopy (NIRS). The primary finding here was a reduced hemodynamic response during the RVIP task. Conclusion: ZA improves aspects of cognitive performance, in particular the speed of performing tasks, in healthy humans and results in concomitant reductions in hemodynamic responses in the frontal cortex during task performance. The findings suggest an increase in neural efficiency following ZA.

Phytochemistry and pharmacology of anti-depressant medicinal plants: A review

Stress renders an individual to experience mental pressure and exhaustion which brings about feelings of anxiety, depression, anger and/or other negative emotions. Depression affects a person's state of mind, behaviour, health and is often associated with suicide. The use of anti-depressant drugs as therapeutic agents is associated with symptoms such as, delayed onset of action, side-effects, drug-drug and dietary interactions, sexual dysfunction, cardiac toxicity, etc. Thus, there is need to target these issues and improve current treatment options. Medicinal plants have long been used in discovering novel treatment strategies and compounds with promising roles in treating various disease conditions. There has been an increase, worldwide, in the use of medicinal plants and herbs for developing nutraceuticals for treatment of depression and other psychiatric disorders. Medicinal plants in their natural forms are valuable as they are rich in various phytochemical compounds. These phytochemical compounds have pharmacological roles in treating various diseases conditions; apart from being widely available in nature and commercially beneficial. The phytochemical compounds in plants are constantly being explored through various experimental studies to determine the molecular basis of how medicinal plants work in relation to drugs and diseases and to develop neutraceuticals for improving conditions. This review summarizes 110 medicinal plants and their phytochemical constituents that have been shown to possess anti-depressant activity. This review also highlights the various mechanisms of anti-depressant action of some of these plants and their plant parts like roots, stem, leaves, flowers, fruit or whole plant; phytochemical compounds showing anti-depressant activity such flavanoids, steroids, saponins, sugars, lectins, alkaloids, etc.; and various anti-depressant screening models used such as tail suspension test, forced swim test, chronic unpredictable stress test, sucrose preference test, monoamine oxidase inhibition assay, learned helplessness test, open field test, hole board test, etc. However, mechanistic evaluation of many of these plants still needs to be investigated and explored.

Spectral and computational features of the binding between riparins and human serum albumin

The green Brazilian bay leaf, a spice much prized in local cuisine (Aniba riparia, Lauraceae), contains chemical compounds presenting benzoyl-derivatives named riparins, which have anti-inflammatory, antimicrobial and anxiolytic properties. However, it is unclear what kind of interaction riparins perform with any molecular target. As a profitable target, human serum albumin (HSA) is one of the principal extracellular proteins, with an exceptional capacity to interact with several molecules, and it also plays a crucial role in the transport, distribution, and metabolism of a wide variety of endogenous and exogenous ligands. To outline the HSA-riparin interaction mechanism, spectroscopy and computational methods were synergistically applied. An evaluation through fluorescence spectroscopy showed that the emission, attributed to Trp 214, at 346 nm decreased with titrations of riparins. A static quenching mechanism was observed in the binding of riparins to HSA. Fluorescence experiments performed at 298, 308 and 318 K made it possible to conduct thermodynamic analysis indicating a spontaneous reaction in the complex formation (ΔG<0). The enthalpy-entropy balance experiment with a molecular modeling calculation revealed that hydrophobic, hydrogen bond and non-specific interactions are present for riparin I-III with HSA. The set of results from fractional fluorescence changes obtained through Schatchard was inconclusive in establishing what kind of cooperativity is present in the interaction. To shed light upon the HSA-riparins complex, Hill's approach was utilized to distinguish the index of affinity and the binding constant. A correspondence between the molecular structures of riparins, due to the presence of the hydroxyl group in the B-ring, with thermodynamic parameters and index of affinity were observed. Riparin III performs an intramolecular hydrogen bond, which affects the Hill coefficient and the binding constant. Therefore, the presence of hydroxyl groups is capable of modulating the interaction between riparins and HSA. Site marker competitive experiments indicated Site I as being the most suitable, and the molecular modeling tools reinforced the experimental results detailing the participation of residues.

Antidepressant-Like Effect of the Leaves of Pseudospondias microcarpa in Mice: Evidence for the Involvement of the Serotoninergic System, NMDA Receptor Complex, and Nitric Oxide Pathway

Depression continues to be a major global health problem. Although antidepressants are used for its treatment, efficacy is often inconsistent. Thus, the search for alternative therapeutic medicines for its treatment is still important. In this study, the antidepressant-like effect of Pseudospondias microcarpa extract (30-300 mg kg(-1), p.o.) was investigated in two predictive models of depression--forced swimming test and tail suspension test in mice. Additionally, the mechanism(s) of action involved were assessed. Acute treatment with the extract dose dependently reduced immobility of mice in both models. The antidepressant-like effect of the extract (100 mg kg(-1), p.o.) was blocked by p-chlorophenylalanine and cyproheptadine but not prazosin, propranolol, or yohimbine. Concomitant administration of D-cycloserine and the extract potentiated the anti-immobility effect. In contrast, D-serine, a full agonist of glycine/NMDA receptors, abolished the effects. Anti-immobility effects of PME were prevented by pretreatment of mice with L-arginine (750 mg kg(-1), i.p.) and sildenafil (5 mg kg(-1), i.p.). On the contrary, pretreatment of mice with L-NAME (30 mg kg(-1), i.p.) or methylene blue (10 mg kg(-1), i.p.) potentiated its effects. The extract produces an antidepressant-like effect in the FST and TST that is dependent on the serotoninergic system, NMDA receptor complex, and the nitric oxide pathway.

Antidepressant-like effect of Hoodia gordonii in a forced swimming test in mice: evidence for involvement of the monoaminergic system

Hoodia gordonii is a plant species used traditionally in southern Africa to suppress appetite. Recently, it has been associated with a significant increase in blood pressure and pulse rate in women, suggesting sympathomimetic activity. The present study investigated the possible antidepressant-like effects of acute and repeated (15 days) administration of H. gordonii extract (25 and 50 mg/kg, po) to mice exposed to a forced swimming test (FST). Neurochemical analysis of brain monoamines was also carried out to determine the involvement of the monoaminergic system on these effects. Acute administration of H. gordonii decreased the immobility of mice in the FST without accompanying changes in general activity in the open-field test during acute treatment, suggesting an antidepressant-like effect. The anti-immobility effect of H. gordonii was prevented by pretreatment of mice with PCPA [an inhibitor of serotonin (5-HT) synthesis], NAN-190 (a 5-HT1A antagonist), ritanserin (a 5-HT2A/2C antagonist), ondansetron (a 5-HT3A antagonist), prazosin (an α1-adrenoceptor antagonist), SCH23390 (a D1 receptor antagonist), yohimbine (an α2-adrenoceptor antagonist), and sulpiride (a D2 receptor antagonist). A significant increase in 5-HT levels in the striatum was detected after acute administration, while 5-HT, norepinephrine and dopamine were significantly elevated after chronic treatment. Results indicated that H. gordonii possesses antidepressant-like activity in the FST by altering the dopaminergic, serotonergic, and noradrenergic systems.