The traditional use of native Brazilian plants for male sexual dysfunction: Evidence from ethnomedicinal applications, animal models, and possible mechanisms of action

ETHNOPHARMACOLOGICAL RELEVANCE

Sexual dysfunction is a multifactorial health condition characterized by distressing disturbances in the sexual response and libido, leading to an inability to maintain penile erection and achieve pleasure. Considering the huge Brazilian biodiversity, many plants are traditionally used for aphrodisiac purposes. However, the use of native medicinal plants as sexual boosters in Brazil has been poorly studied.

AIM OF THE STUDY

This review focuses on the composition, pharmacology, and results of experimental trials of the main native plants used in Brazilian folk medicine with alleged aphrodisiac effects. We aimed to provide a state-of-the-art reference for research on herbs for the treatment of male sexual dysfunction by summarizing and discussing the main studies found.

MATERIALS AND METHODS

The relevant information was collected by searching keywords (aphrodisiac, sexual tonic, sexual stimulant, sexual vigor stimulant, sexual impotency, erectile dysfunction, etc.) from books containing primary surveys conducted in the original communities and bibliographic surveys prepared by authors linked to the national academic and scientific environment edited in Brazil. Preclinical and clinical studies of the compiled plant species were performed using scientific databases (Scopus, PubMed, SciELO, and SciFinder).

RESULTS

Seventy-four plant species belonging to 44 families used in Brazil to treat sexual dysfunction were compiled from ethnopharmacological literature. Fourteen plants, including Pfaffia glomerata (Spreng.) Pedersen, Aspidosperma quebracho-blanco Schltdl., Anemopaegma arvense (Vell.) Stellfeld ex de Souza, Mimosa pudica L., Heteropterys tomentosa A. Juss., Trichilia catigua A. Juss., and Turnera diffusa Willd. ex Schult. were pharmacologically studied to confirm these therapeutic properties. Probable modes of action include antioxidant and androgenic activities, inhibition of the PDE5 enzyme, increase in NO levels, and activation of dopaminergic and noradrenergic pathways. In addition, several different species popularly known as "catuaba" were identified, leading to adulterations and controversial effects.

CONCLUSION

The overall results of the present review of Brazilian folk literature reveal that Brazil has a long tradition of using plants with potential aphrodisiac effects. However, further research is required to identify, characterize, and standardize the active ingredients and herbal preparations used in aphrodisiacs.

Natural product-based pharmacological studies for neurological disorders

Central nervous system (CNS) disorders and diseases are expected to rise sharply in the coming years, partly because of the world's aging population. Medicines for the treatment of the CNS have not been successfully made. Inadequate knowledge about the brain, pharmacokinetic and dynamic errors in preclinical studies, challenges with clinical trial design, complexity and variety of human brain illnesses, and variations in species are some potential scenarios. Neurodegenerative diseases (NDDs) are multifaceted and lack identifiable etiological components, and the drugs developed to treat them did not meet the requirements of those who anticipated treatments. Therefore, there is a great demand for safe and effective natural therapeutic adjuvants. For the treatment of NDDs and other memory-related problems, many herbal and natural items have been used in the Ayurvedic medical system. Anxiety, depression, Parkinson's, and Alzheimer's diseases (AD), as well as a plethora of other neuropsychiatric disorders, may benefit from the use of plant and food-derived chemicals that have antidepressant or antiepileptic properties. We have summarized the present level of knowledge about natural products based on topological evidence, bioinformatics analysis, and translational research in this review. We have also highlighted some clinical research or investigation that will help us select natural products for the treatment of neurological conditions. In the present review, we have explored the potential efficacy of phytoconstituents against neurological diseases. Various evidence-based studies and extensive recent investigations have been included, which will help pharmacologists reduce the progression of neuronal disease.

Four Clerodane Diterpenoids From Ptychopetalum Olacoides

A phytochemical component investigation of the bark of Ptychopetalum olacoides led to the isolation of 4 new clerodane-type diterpenoids, namely, ptycholide V (1), 7α,20-dihydroxykolavelool (2), ptycholide VI (3), and ptycholide VII (4). Their structures were elucidated by extensive spectroscopic data and comparison of NMR data with that obtained for known compounds.

Natural Products for the Treatment of Post-stroke Depression

Post-stroke depression (PSD) is the most frequent and important neuropsychiatric consequence of stroke. It is strongly associated with exacerbated deterioration of functional recovery, physical and cognitive recoveries, and quality of life. However, its mechanism is remarkably complicated, including the neurotransmitters hypothesis (which consists of a monoaminergic hypothesis and glutamate-mediated excitotoxicity hypothesis), inflammation hypothesis, dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis, and neurotrophic hypothesis and neuroplasticity. So far, the underlying pathogenesis of PSD has not been clearly defined yet. At present, selective serotonin reuptake inhibitors (SSRIs) have been used as the first-line drugs to treat patients with PSD. Additionally, more than SSRIs, a majority of the current antidepressants complied with multiple side effects, which limits their clinical application. Currently, a wide variety of studies revealed the therapeutic potential of natural products in the management of several diseases, especially PSD, with minor side effects. Accordingly, in our present review, we aim to summarize the therapeutic targets of these compounds and their potential role in-clinic therapy for patients with PSD.

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.

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.

Potential plant-derived catecholaminergic activity enhancers for neuropharmacological approaches: A review

BACKGROUND

Catecholamines (CAs) have been reported to be involved in numerous functions including central nervous system. CA release from the intra neuronal storage vesicles aid in the therapy of various neurological and neuropsychiatric disorders where the catecholaminergic neurotransmission is compromised. Bioavailability of CA at the synapse can be increased through stimulated neurotransmitter release, monoamine oxidase and CA reuptake inhibition. Plant based galenicals are reported to have similar CA enhancement activities and have been used for the management of neurological disorders.

AIM

To review evidence-based literature with plant extracts, bioactive compounds, and composite extracts that modulate central catecholaminergic system, thereby enhancing CA activity for beneficial neurological effect.

METHODS

Electronic databases such as PubMed, Scopus, and ScienceDirect were used to search scientific contributions until January 2018, using relevant keywords. Literature focusing plant-derived CA enhancing compounds, extracts and/or composite extracts were identified and summarized. In all cases, dose, route of administration, the model system and type of extract were accounted.

RESULTS

A total of 49 plant extracts, 31 compounds and 16 herbal formulations have shown CA activity enhancement. Stimulated CA release from the storage vesicles, monoamine oxidase and CA reuptake inhibition were the major mechanisms involved in the increase of CA bioavailability by these phytoconstituents.

CONCLUSION

This review provides an overview on the phytoconstituents with CA enhancement property that have been used for neuropsychiatric disorders. Such herbal remedies will provide an avenue for cost effective and easily available medication which have holistic approach towards disease management. There is also scope for alternate medicines or prototype drug development utilizing these phytomedicines for treating neurodegenerative diseases. However, hurdles are to be met for analyzing the mode and mechanism of action associated with these phytomedicines and their proper scientific documentation.

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.

Natural products against Alzheimer's disease: Pharmaco-therapeutics and biotechnological interventions

Alzheimer's disease (AD) is a severe, chronic and progressive neurodegenerative disease associated with memory and cognition impairment ultimately leading to death. It is the commonest reason of dementia in elderly populations mostly affecting beyond the age of 65. The pathogenesis is indicated by accumulation of the amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFT) in brain tissues and hyperphosphorylation of tau protein in neurons. The main cause is considered to be the formation of reactive oxygen species (ROS) due to oxidative stress. The current treatment provides only symptomatic relief by offering temporary palliative therapy which declines the rate of cognitive impairment associated with AD. Inhibition of the enzyme acetylcholinesterase (AChE) is considered as one of the major therapeutic strategies offering only symptomatic relief and moderate disease-modifying effect. Other non-cholinergic therapeutic approaches include antioxidant and vitamin therapy, stem cell therapy, hormonal therapy, use of antihypertensive or lipid-lowering medications and selective phosphodiesterase (PDE) inhibitors, inhibition of β-secretase and γ-secretase and Aβ aggregation, inhibition of tau hyperphosphorylation and intracellular NFT, use of nonsteroidal anti-inflammatory drugs (NSAIDs), transition metal chelators, insulin resistance drugs, etanercept, brain-derived neurotrophic factor (BDNF) etc. Medicinal plants have been reported for possible anti-AD activity in a number of preclinical and clinical trials. Ethnobotany, being popular in China and in the Far East and possibly less emphasized in Europe, plays a substantial role in the discovery of anti-AD agents from botanicals. Chinese Material Medica (CMM) involving Chinese medicinal plants has been used traditionally in China in the treatment of AD. Ayurveda has already provided numerous lead compounds in drug discovery and many of these are also undergoing clinical investigations. A number of medicinal plants either in their crude forms or as isolated compounds have exhibited to reduce the pathological features associated with AD. In this present review, an attempt has been made to elucidate the molecular mode of action of various plant extracts, phytochemicals and traditional herbal formulations investigated against AD as reported in various preclinical and clinical tests. Herbal synergism often found in polyherbal formulations were found effective to combat disease heterogeneity as found in complex pathogenesis of AD. Finally a note has been added to describe biotechnological improvement, genetic and genomic resources and mathematical and statistical techniques for empirical model building associated with anti-AD plant secondary metabolites and their source botanicals.

The ethnobotany of psychoactive plant use: a phylogenetic perspective

Psychoactive plants contain chemicals that presumably evolved as allelochemicals but target certain neuronal receptors when consumed by humans, altering perception, emotion and cognition. These plants have been used since ancient times as medicines and in the context of religious rituals for their various psychoactive effects (e.g., as hallucinogens, stimulants, sedatives). The ubiquity of psychoactive plants in various cultures motivates investigation of the commonalities among these plants, in which a phylogenetic framework may be insightful. A phylogeny of culturally diverse psychoactive plant taxa was constructed with their psychotropic effects and affected neurotransmitter systems mapped on the phylogeny. The phylogenetic distribution shows multiple evolutionary origins of psychoactive families. The plant families Myristicaceae (e.g., nutmeg), Papaveraceae (opium poppy), Cactaceae (peyote), Convolvulaceae (morning glory), Solanaceae (tobacco), Lamiaceae (mints), Apocynaceae (dogbane) have a disproportionate number of psychoactive genera with various indigenous groups using geographically disparate members of these plant families for the same psychoactive effect, an example of cultural convergence. Pharmacological traits related to hallucinogenic and sedative potential are phylogenetically conserved within families. Unrelated families that exert similar psychoactive effects also modulate similar neurotransmitter systems (i.e., mechanistic convergence). However, pharmacological mechanisms for stimulant effects were varied even within families suggesting that stimulant chemicals may be more evolutionarily labile than those associated with hallucinogenic and sedative effects. Chemically similar psychoactive chemicals may also exist in phylogenetically unrelated lineages, suggesting convergent evolution or differential gene regulation of a common metabolic pathway. Our study has shown that phylogenetic analysis of traditionally used psychoactive plants suggests multiple ethnobotanical origins and widespread human dependence on these plants, motivating pharmacological investigation into their potential as modern therapeutics for various neurological disorders.

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 extract from Polygala paniculata: involvement of the monoaminergic systems

CONTEXT

Polygala paniculata Linnaeus (Polygalaceae) has shown neuroprotective effects, but there is no report about its antidepressant potential.

OBJECTIVE

The antidepressant-like effect of the hydroalcoholic extract from P. paniculata and some of the possible mechanisms involved in this effect were investigated in forced swimming test (FST).

MATERIALS AND METHODS

Mice received extract by oral route and were submitted to FST and open-field test. Animals were forced to swim and the total immobility time was registered (6-min period). A reduction in the immobility time is considered an antidepressant-like effect. In order to investigate the involvement of the monoaminergic systems, mice were treated with pharmacological antagonists before administration of the extract.

RESULTS

The acute administration of the hydroalcoholic extract from P. paniculata produced an antidepressant-like effect, since it significantly reduced the immobility time in FST (0.01-30 mg/kg) as compared to control group, without changing locomotor activity. Pretreatment of mice with yohimbine (1 mg/kg, i.p., α₂-adrenoceptor antagonist), propranolol (1 mg/kg, i.p., β-adrenoceptor antagonist), SCH23390 (0.05 mg/kg, s.c., dopamine D₁ receptor antagonist) or sulpiride (50 mg/kg, i.p., dopamine D₂ receptor antagonist) prevented the antidepressant-like effect of the extract in FST (30 mg/kg). Moreover, ketanserin (5 mg/kg, i.p., preferential 5-HT(2A) receptor antagonist) enhanced the effect of the extract in FST.

DISCUSSION AND CONCLUSION

The results of the present study indicate that the extract from P. paniculata has an antidepressant-like action that is likely mediated by an interaction with the serotonergic (5-HT2A receptors), noradrenergic (α₂ and β-receptor) and dopaminergic (D₁ and D₂ receptors) systems.

Anti-stress effects of the "tonic"Ptychopetalum olacoides (Marapuama) in mice

With the recognition that high levels of sustained stress are associated with the natural course of countless illnesses, effective anti-stress agents have gained importance. Improved endurance to particularly stressful periods is one of the medicinal claims for Marapuama (Ptychopetalum olacoides Bentham, PO), a popular Amazonian herbal. The purpose of this study was to evaluate if PO possesses anti-stress properties. To this end, an extract from PO (POEE) was evaluated on anxiety and glucose levels in mice submitted to the unpredictable chronic mild stress (UCMS) paradigm. POEE did not present anxiolytic effects, but was able to prevent (p<0.01) the UCMS-induced anxiety as assessed by the light/dark test (time spent in the lit area, POEE 100 and 300mg/kg 235.9+/-20.6s and 250.4+/-17.4s, respectively, compared to DMSO 104.7+/-24.4s). Likewise, although POEE did not induce noticeable effects on glycemia, it effectively (p<0.01) prevented the UCMS-induced hyperglycemia (POEE 100 and 300mg/kg 106.4+/-6.7mg/dl and 107.3+/-3.3mg/dl, respectively, compared to DMSO 134.6+/-5.9mg/dl). Additionally, POEE (50-200mg/kg i.p. and 800mg/kg p.o.) significantly (p<0.01 and p<0.05, respectively) increased the time to hypoxia-induced convulsion (by 38%, 51%, 59% and 27%, respectively for i.p. and p.o. treatments). The data indicate that POEE counteracts some of the effects brought about by chronic stress. This study combined with the identified antioxidant and neuroprotective properties, as well as the claimed benefits associated with stressful periods suggest that Ptychopetalum olacoides (Marapuama) might possess adaptogen-like properties.