Screening of plants used in southern Africa for epilepsy and convulsions in the GABAA-benzodiazepine receptor assay

A review on epilepsy, current treatments, and potential of medicinal plants as an alternative treatment

Epilepsy is considered common neurological diseases that threaten the lives of millions of people all around the world. Since ancient times, different forms of medications have been used to treat this condition. Adverse events associated with treatments and the residence time of available drugs caused to search for safer and more efficient therapies and drugs remain one of the major areas of research interest for scientists. As one of the therapeutics with fewer side effects, plants and their essential oils can be considered replacements for existing treatments. Medicinal plants have proven to be an effective natural source of antiepileptic drugs; most of them have their mechanism of action by affecting GABA receptors in different paths. Cannabis indica and Cymbopogon winterianus are well-known plant species with antiepileptic activities. The current review presenting a list of plants with antiepileptic effects aims to pave the way for finding alternative drugs with fewer side effects for scientists.

Medicinal plants of the upper Aswa River catchment of northern Uganda - a cultural crossroads

BACKGROUND

This paper presents a comparative inventory of medicinal plant taxa and their uses by smallholder farming communities of four cultures in the Aswa River catchment of northern Uganda, situated in the eastern Sudanian savanna parkland ecotype of sub-Saharan Africa. The purpose of the study was to document the ethnobotanical use of medicinal plants by the Lango, Acholi, Teso (Atesot) and Ethur (jo Abwor), in an historical moment before civil conflict and mass displacement of the respondent communities disrupted the inter-generational transmission of traditional technical knowledge within the study area.

METHODS

Following community consultations in four districts of northern Uganda during 1999-2000, interviews were conducted with holders of specialist knowledge on plants used as medicine on basis of a plant specimen allocated a voucher number and identified by the national herbarium. Use reports reflecting specific medicinal applications were compiled in aggregate to obtain a Relative Importance Index ranking. The commonality of medicinal taxa cited between each cultural interface was assessed by the Jaccard Index of Similarity, and the similarity of specific medicinal usage by taxon using Rahman's Similarity Index.

RESULTS

The data collected from 112 respondents comprise 280 medicinal use reports describing 263 applications for 62 medical conditions, citing 108 taxa from 44 botanical families of which Fabaceae comprised 20% of all use reports. No earlier mention could be found to corroborate 72 use reports (27% of the total), representing medicinal indications as yet undocumented, and potentially worthy of investigation. The RI values ranged between 15 and 94%, with 13 taxa having RI values above 50%. The JI ratios indicate the highest degree of similarity in the plant taxa used as medicine (21%) between the Lango and Teso cultures who share a common origin; however, Rahman's Similarity Index indicates the highest similarity of specific medicinal usage by taxon between the Lango and Acholi, who share a common language group through cultural assimilation over time.

CONCLUSIONS

As a comparative study, the results imply that cultural exchange and assimilation may be a greater driver of inter-cultural similarity of ethnopharmacological use of a given taxon, as compared to shared historical origins.

In vitro and in vivo anti-seizure activity of hydromethanolic extract and fractions of Pterolobium stellatum

ETHNOPHARMACOLOGICAL RELEVANCE

In Ethiopia, the whole plant juice of Pterolobium stellatum is used to treat seizures and epilepsy.

AIM OF THE STUDY

To investigate the antiseizure activity of hydromethanolic crude extract and fractions collected from leaves of P. stellatum using both in vitro, and in vivo seizure models in mice.

MATERIALS AND METHODS

Fresh leaves of P. stellatum were collected from Awash Melka, Addis Ababa, Ethiopia. An 80% crude methanol extract was further fractionated to produce petroleum ether, chloroform, butanol, and aqueous fractions. Anti-seizure activity of the crude extract and fractions (petroleum ether, chloroform, butanol, and water) were assessed at a concentration of 0.7 mg/ml using the in vitro 0 Mg²⁺ model of seizures in mouse brain slices prepared from 14- to 21-day-old C57BL/6 mice. The maximal electroshock seizure (MES) model and the pentylenetetrazol (PTZ) seizure model for seizures were performed on male BALB/c mice using 400 mg/kg and 800 mg/kg of crude 80% methanol extract, as well as the four fractions described above. Diazepam and phenytoin were used as positive controls for PTZ and MES test respectively.

RESULTS

Addition of 0.7 mg/ml of crude 80% methanol extract of P. stellatum prevented the onset of SLEs in most brain slices in the 0 Mg²⁺in vitro model of seizures, with similar efficacy to diazepam (3 μM). The same extract at 400 and 800 mg/kg was efficacious in reducing the hindlimb extension time in the MES model and delaying the onset of myoclonic convulsions in the PTZ model, although not to the same extent as phenytoin (10 mg/kg) or diazepam (5 mg/kg). The chloroform and water fractions of the crude extract also showed significant anti-seizure activity across all three models whilst the non-polar petroleum ether and butanol fractions did not. The UPLC-MS analysis indicated the presence of gallic acid, ellagic acid, kaempferol, myricitrin, isoquercitrin and quercitirin in the crude extract. Gallic acid and ellagic acid were observed in chloroform fraction and in the water fraction ellagic acid, kaempferol, myricitrin and isoquercitrin were detected.

CONCLUSION

The crude hydromethanolic extract of P. stellatum has significant anti-seizure activity. The chloroform and aqueous fractions have antiseizure activity. The extracts have previously identified compounds with anticonvulsant activity which indicates the antiseizure potential of the plant.

Sedative–Hypnotic Activity of the Water Extracts of Coptidis Rhizoma in Rodents

Many medicinal plants have been used in Asia for treating a variety of mental diseases, including insomnia and depression. However, their sedative–hypnotic effects and mechanisms have not been clarified yet. Accordingly, the objective of this study was to investigate the sedative–hypnotic effects of water extracts of five medicinal plants: Coptidis Rhizoma, Lycii Fructus, Angelicae sinensis Radix, Bupleuri Radix, and Polygonum multiflorum Thunberg. The binding abilities of five medicinal plant extracts to the GABA_A–BZD and 5-HT_2C receptors were compared. Their abilities to activate arylalkylamine N-acetyltransferase (AANAT), a melatonin synthesis enzyme, in pineal cells were also determined. Following in vitro tests, the sedative and hypnotic activities of extracts with the highest activities were determined in an animal sleep model. In the binding assay, the water extracts of Coptidis Rhizoma (WCR) showed high binding affinity to the GABA_A–BZD and 5-HT_2C receptors in a dose-dependent manner. Additionally, WCR increased the AANAT activity up to five times compared with the baseline level. Further animal sleep model experiments showed that WCR potentiated pentobarbital-induced sleep by prolonging the sleep time. It also decreased the sleep onset time in mice. In addition, WCR reduced wake time and increased non-rapid eye movement (NREM) sleep without EEG power density (percentages of δ, θ, and α waves) during NREM sleep in rats. WCR could effectively induce NREM sleep without altering the architectural physiologic profile of sleep. This is the first report of the sedative–hypnotic effect of Coptidis Rhizoma possibly by regulating GABA_A and 5-HT_2C receptors and by activating AANAT activity.

Anti-seizure effects of medicinal plants in Malawi on pentylenetetrazole-induced seizures in zebrafish larvae

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants are used to manage and treat epilepsy in Malawi because of traditional beliefs and barriers to conventional anti-seizure drugs. Among the plants prescribed by traditional medical practitioners are Margaritaria discoidea, Dalbergia boehmii, Dalbergia nitidula, Catunaregam spinosa, and Lannea discolor. Despite the wide use of these plants, there is a lack of scientific evidence to support their anti-seizure efficacy.

AIM OF THE STUDY

This study used the pentylenetetrazole (PTZ)-induced larval zebrafish seizure model to screen for anti-seizure effects of a collection of medicinal plants traditionally used in Malawi.

MATERIALS AND METHODS

Zebrafish larvae were incubated in decoctions at maximum tolerated concentrations for 18 h and exposed to PTZ. As a primary screen, the effects of the decoctions on seizure-induced locomotor activity were determined. Decoctions that significantly reduced total distance traveled were further checked for effects on seizure latency and frequency, brain activity, immediate early gene expression, and c-fos protein expression.

RESULTS

M. discoidea male leaves, D. boehmii roots, and D. nitidula leaves showed significant anti-seizure effects in the primary screen and were selected for further study. Electrophysiological and immediate early gene analyses corroborated anti-seizure effect of D. boehmii and D. nitidula. The results of c-fos protein expression further suggested that the anti-seizure effects in the larval brain may be mediated by the suppression of neurons localized in midbrain regions.

CONCLUSIONS

These findings provide pioneering scientific evidence of the presence of anti-seizure activity in M. discoidea, D. boehmii, and D. nitidula, prescribed by traditional Malawian medical practitioners. Further studies are needed to identify and isolate compounds responsible for such biological activities and elucidate the possible mechanisms of action.

Binding activity of Valeriana fauriei root extract on GABAA receptor flunitrazepam sites and distribution of its active ingredients in the brain of mice - A comparison with that of V. officinalis root

ETHNOPHARMACOLOGICAL RELEVANCE

Valeriana fauriei root (VF) is a crude drug registered in the Japanese Pharmacopeia 17th Edition and a known substitute for V. officinalis (VO). Although VO has been pharmacologically evaluated for its sedative effects and mechanism of action, data regarding VF remain scarce.

AIM OF THE STUDY

We compared the binding affinity of VF and VO extracts, as well as examined the active ingredients in the VF extract, on flunitrazepam sites of γ-aminobutyric acid receptor type A (GABA_A receptor). Furthermore, we confirmed whether these active ingredients were distributed in the brain of mice orally administered the VF extract.

MATERIALS AND METHODS

We prepared the assay system to evaluate the binding activity of flunitrazepam sites of GABA_A receptor using a 96-well plate and assessed the activities of VF and VO extracts. We then analyzed their constituents using HPLC with principal component analysis (PCA) and evaluated active ingredients correlated with their activities. The distribution of active ingredients in the plasma and brain of mice orally administered the VF extract prepared with different emulsifiers were analyzed by LC-MS/MS.

RESULTS

The ethanol extract of VF exhibited significantly higher activity on flunitrazepam sites of GABA_A receptor than VO. For the VF extract, kessyl glycol diacetate (KGD) was markedly associated with the binding activities; however, active ingredients included KGD, kessyl glycol 8-acetate (KG8), α-kessyl acetate (α-KA), and coniferyl isovalerate (CI). For VO, valerenic acid and five other compounds were associated with the binding affinity on flunitrazepam sites of GABA_A receptor. On emulsifying the VF extract with a fat-soluble glycerin fatty acid ester, the plasma and brain distributions of KGD tended to be higher, those of KG8 were significantly more than 10-times higher, and those of α-KA was lower than those of the VF extract emulsified with water-soluble gum arabic, after oral administration in mice.

CONCLUSIONS

Based on the binding activity on flunitrazepam sites of GABA_A receptor and brain distribution, KGD, KG8, and α-KA can be considered active ingredients of VF. The addition of a fat-soluble emulsifier promoted the absorption of KGD, the main active ingredient, and KGD was metabolized to KG8 in the body. The present results suggest a possible mechanism underlying the sedative effect for VF, and these three compounds can be used as marker compounds to evaluate the quality of VF products.

The Botanical, Chemical and Ethnobotanical Diversity of Southern African Lamiaceae

The Lamiaceae is undoubtedly an important plant family, having a rich history of use that spans the globe with many species being used in folk medicine and modern industries alike. Their ability to produce aromatic volatile oils has made them valuable sources of materials in the cosmetic, culinary, and pharmaceutical industries. A thorough account of the taxonomic diversity, chemistry and ethnobotany is lacking for southern African Lamiaceae, which feature some of the region’s most notable medicinal and edible plant species. We provide a comprehensive insight into the Lamiaceae flora of southern Africa, comprising 297 species in 42 genera, 105 of which are endemic to the subcontinent. We further explore the medicinal and traditional uses, where all genera with documented uses are covered for the region. A broad review of the chemistry of southern African Lamiaceae is presented, noting that only 101 species (34%) have been investigated chemically (either their volatile oils or phytochemical characterization of secondary metabolites), thus presenting many and varied opportunities for further studies. The main aim of our study was therefore to present an up-to-date account of the botany, chemistry and traditional uses of the family in southern Africa, and to identify obvious knowledge gaps.

Quercetin-3-O-glucuronide in the Ethanol Extract of Lotus Leaf (Nelumbo nucifera) Enhances Sleep Quantity and Quality in a Rodent Model via a GABAergic Mechanism

Current pharmacological treatments for insomnia carry several and long-term side effects. Therefore, natural products without side effects are warranted. In this study, the sleep-promoting activity of the lotus leaf (Nelumbo nucifera) extract was assessed using ICR mice and Sprague Dawley rats. A pentobarbital-induced sleep test and electroencephalogram analysis were conducted to measure sleep latency time, duration, and sleep architecture. The action mechanism of the extract was evaluated through ligand binding experiments. A high dose (300 mg/kg) of the ethanolic lotus leaf extract significantly increased sleep duration compared to the normal group (p < 0.01). Administration of low (150 mg/kg) and high doses (300 mg/kg) of the extract significantly increased sleep quality, especially the relative power of theta waves (p < 0.05), compared to the normal group. Furthermore, caffeine and lotus leaf extract administration significantly recovered caffeine-induced sleep disruption (p < 0.001), and the sleep quality was similar to that of the normal group. Additionally, ligand binding assay using [3H]-flumazenil revealed that quercetin-3-O-glucuronide contained in the lotus leaf extract (77.27 μg/mg of extract) enhanced sleep by binding to GABAA receptors. Collectively, these results indicated that the lotus leaf extract, particularly quercetin-3-O-glucuronide, exhibits sleep quantity- and quality-enhancing activity via the GABAergic pathway.

A review of traditional uses, phytochemistry and pharmacology of the genus Indigofera

ETHNOPHARMACOLOGICAL RELEVANCE

Indigofera is the third-largest genus in the family of Fabaceae, with approximately 750 species. It is distributed across all tropical regions. Indigofera species are widely employed in traditional medicine all around the world, against many ailments. Thus, based on these medicinal properties, various investigations have been undertaken in order to appraise the pharmacological activities and the chemical composition of these species. A recent paper provides a summary of the phytochemistry and pharmacology of the genus Indigofera. Consequently, this review is a continuation of this previous study by updating some data and adding information about the phylogeny and traditional uses of the genus.

AIM OF THE STUDY

To provide an overview of the phylogeny, traditional uses, phytochemistry, pharmacology and toxicity of the genus Indigofera, and to identify the remaining gaps and thus supply a basis for further investigations.

MATERIALS AND METHODS

A review of the literature was performed by consulting scientific databases such as 'ScienceDirect', 'PubMed', 'Google Scholar' and 'SpringerLink' and using the keyword Indigofera.

RESULTS

Over 60 Indigofera species are reported in traditional medicine. The uses depend on the country and the species, but similarities have been noticed. Indeed, treatments of gastrointestinal disorders, inflammatory conditions and pain, skin ailments, and respiratory and infectious diseases are recurring. Phytochemical studies have led to the identification of more than 200 compounds, notably flavonoids and terpenoids. Many pharmacological activities have been demonstrated, particularly antimicrobial, cytotoxic and anti-inflammatory activities, and thus allowed to assert most of the traditional uses of the genus. Some active compounds have been isolated and have shown remarkable therapeutic potential, like the alkaloid indirubin, which is currently being clinically trialed.

CONCLUSIONS

The data on the genus Indigofera are extensive, but gaps still remain. Indeed, some promising species have not been assessed for their phytochemistry and/or pharmacology and thus remain unexplored. Moreover, relatively few active compounds have been isolated and tested for their biological activity, and studies to explain their mechanism of action are nearly inexistent. Furthermore, some pharmacological studies have inappropriate methodologies that make the results difficult to interpret. Consequently, further in-depth and relevant research is required to supplement the knowledge on this wide-ranging genus and to confirm its reported therapeutic potential.

Phytochemical Diversity and Pharmacological Properties of Rhus coriaria

Rhus coriaria L. (Anacardiaceae), sumac, is a common condiment, appetizer and souring agent in the Mediterranean region that has a long history in traditional medicine. R. coriaria has been prescribed for the treatment of many ailments including diarrhea, ulcer, hemorrhoids, hemorrhage, wound healing, hematemesis, and eye ailments like ophthalmia and conjunctivitis. The plant is also used as diuresis, antimicrobial, abortifacient and as a stomach tonic. Sumac is known to be rich in different classes of phytochemicals including tannins, polyphenols, flavonoids, organic acids and essential oils and continues to be a hot topic for extensive research work designed for revealing its phytochemical constituents and evaluating its bioactive properties. This review summarizes the recent phytochemical and diverse bioactivity studies on R. coriaria, especially those concerned with antitumor, antioxidant, hypoglycemic, antimicrobial, and anti-inflammatory studies.

Review: Southern African medicinal plants used as blood purifiers

ETHNOPHARMALOGICAL RELEVANCE

Blood purification practices, also referred to as blood cleansing or detoxification, is an ancient concept which is widespread amongst African traditional medicine, but for which no modern scientific basis exists. There prevails considerable ambiguity in defining what a blood purifier is.

AIM OF THE STUDY

The purpose of this review is to firstly define what a blood purifier is in the context of African traditional medicine and compare to other cultural and westernized interpretations. Thereafter, this study identifies traditionally used medicinal plants used as blood purifiers in southern Africa and correlates these species to scientific studies, which may support evidence for these "blood purifying plant species".

MATERIALS AND METHODS

Ethnobotanical books and review articles were used to identify medicinal plants used for blood purification. Databases such as Scopus, ScienceDirect, PubMed and Google Scholar were used to source scientific articles. An evaluation was made to try correlate traditional use to scientific value of the plant species.

RESULTS

One hundred and fifty nine plant species have been documented as traditional remedies for blood purification. Most of the plant species have some pharmacological activity, however, very little link to the traditional use for blood purification. There has been some justification of the link between blood purification and the use as an antimicrobial and this has been explored in many of the plant species identified as blood purifiers. Other pharmacological studies specifically pertaining to the blood require further attention.

CONCLUSION

Irrespective of the ambiguity of interpretation, medicinal plants used to "cleanse the blood", play an important holistic role in traditional medicine and this review with recommendations for further study provides some value of exploring this theme in the future.

Sleep Promoting Effect of Luteolin in Mice via Adenosine A1 and A2A Receptors

Luteolin, a widespread flavonoid, has been known to have neuroprotective activity against various neurologic diseases such as epilepsy, and Alzheimer’s disease. However, little information is available regarding the hypnotic effect of luteolin. In this study, we evaluated the hypnotic effect of luteolin and its underlying mechanism. In pentobarbital-induced sleeping mice model, luteolin (1, and 3 mg/kg, p.o.) decreased sleep latency and increased the total sleep time. Through electroencephalogram (EEG) and electromyogram (EMG) recording, we demonstrated that luteolin increased non-rapid eye movement (NREM) sleep time and decreased wake time. To evaluate the underlying mechanism, we examined the effects of various pharmacological antagonists on the hypnotic effect of luteolin. The hypnotic effect of 3 mg/kg of luteolin was not affected by flumazenil, a GABAA receptor-benzodiazepine (GABAAR-BDZ) binding site antagonist, and bicuculine, a GABAAR-GABA binding site antagonist. On the other hand, the hypnotic effect of 3 mg/kg of luteolin was almost completely blocked by caffeine, an antagonist for both adenosine A1 and A2A receptor (A1R and A2AR), 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX), an A1R antagonist, and SCH-58261, an A2AR antagonist. From the binding affinity assay, we have found that luteolin significantly binds to not only A1R but also A2AR with IC₅₀ of 1.19, 0.84 μg/kg, respectively. However, luteolin did not bind to either BDZ-receptor or GABAAR. From these results, it has been suggested that luteolin has hypnotic efficacy through A1R and A2AR binding.

Herbal medicine for epilepsy seizures in Asia, Africa and Latin America: A systematic review

RELEVANCE

More than 70 million people suffer epilepsy worldwide. Low availability of anti-epileptic drugs, side-effects and drug-resistant epilepsy affect the quality of life of persons with epilepsy in countries with a poorly developed health system. Herbal medicine is frequently used for this neurological condition.

OBJECTIVES

The main objective was to provide a detailed analysis of Herbal Medicine used for neurological conditions related with epilepsy in Asia, Africa and Latin America. More broadly, this study aims to highlight species with assessed efficacy (cross-cultural use, pharmacological effects on models of epileptic seizures) and safety (toxicological data in laboratory) information, in order to point out species of interest for further studies. A critical assessment of models used in pharmacological evaluations was done.

MATERIALS AND METHODS

The systematic search for Herbal Medicine treatments for epilepsy was performed considering all the articles published until February 2017 through three scientific databases. It was made with MeSH terms and free text defining the epilepsy seizures and plant species. We included studies carried out in Asia, Africa and Latin America. All articles reporting the use of Herbal Medicine to treat epilepsy seizures and/or their pharmacological evaluation were retained for further analysis.

RESULTS

The search yielded 1886 articles, from 30 countries. Hundred and six articles published between 1982 and 2017 were included, corresponding to a total of 497 use reports for 351 plant species belonging to 106 families. Three hundred and seventy seven use reports corresponding to 264 species in ethnopharmacological surveys and 120 evaluation reports corresponding to 107 species were noted. Twenty-nine reports, for 29 species, combined both ethnopharmacological and pharmacological evaluation. Fifty eight studies originated from Africa, 35 studies from Asia and 18 from Latin America. Highest use report was noted for rhizomes of Acorus calamus L. (12 use report in 1 country) and leaves of Bacopa monnieri (L.) Wettst. (8 use report in 2 countries). Therefore these species display the highest use convergence. Regarding pharmacological evaluation most studied species were: Leonotis leonurus (L.) R.Br. (4 evaluation reports in 1 country), Uncaria rhynchophylla (Miq.) Miq. ex Havil. (3 evaluation reports in 2 countries) and Calotropis gigantea (L.) Dryand. (3 evaluation reports in 1 country). In vivo models of chronic epilepsy were more relevant than in vitro models or chemical models inducing acute seizures for pharmacological assessment.

CONCLUSION

Species with the highest use report were not those with pharmacological evaluation. It will be pertinent to assess the pharmacological effects and safety of medicinal plants used mostly by traditional healers on predictive models of seizures.

Effectiveness of the Sleep Enhancement by Green Romaine Lettuce (Lactuca sativa) in a Rodent Model

This study was conducted to investigate the effects of the extracts of green romaine lettuce (GRE) on sleep enhancement. GRE contains 1071.7 and 199.2 µg/g of extracts of lactucin and lactucopicrin, respectively, known as sleep enhancement substances. When 100 mg/kg of GRE was administered orally, sleep latency and duration time were significantly increased compared to controls (p < 0.05). Rapid eye movement (REM) sleep decreased with 100 mg/kg of GRE administration and non-REM (NREM) sleep also increased. There was no significant difference between REM and NREM among the oral GRE administration groups receiving 100, 120, and 160 mg/kg GRE. In the caffeine-induced insomnia model, total sleep time was significantly increased by 100 mg/kg GRE administration compared to the caffeine-treated group (p < 0.05). In addition, GRE inhibited the binding of [3H]-flumazenil in a concentration-dependent manner, and affinity of both lactucin and lactucopicrin to gamma-aminobutyric acid (GABA)A-benzodiazepine (BDZ) receptor was 80.7% and 55.9%, respectively. Finally, in the pentobarbital-induced sleep mouse model, the sleep enhancement effect of GRE was inhibited by flumazenil, an antagonist of BDZ. Thus, these results demonstrate that GRE acts via a GABAergic mechanism to promote sleep in a rodent model.

Isolation of a sleep-promoting compound from Polygonatum sibiricum rhizome

The aim of this study was to identify sleep-promoting substance from Polygonatum sibiricum rhizome extract (PSE) with the regulation of sleep architecture. PSE showed a decrease in sleep latency time and an increase in the sleeping time. In the electroencephalography analysis of rats, PSE (150 mg/kg) showed an increase of non-rapid eye movement by 38% and a decrease of rapid eye movement by 31% compared to the control. This sleep-promoting activity was found to be involved in the GABAA-BDZ receptor. The chemical structure of the pure compound was determined by the 1H and 13C nuclear magnetic resonance spectroscopy and gas chromatography mass spectrometry analysis; active compound was glyceryl-1-monolinoleate. The commercial standard glyceryl-1-monolinoleate showed a similar inhibitory concentration on [3H]-flumazenil binding to GABAA-BDZ receptors with final active fraction of PSE. The results indicate that glyceryl-1-monolinoleate is a major active compound responsible for the PSE-derived sleep promotion.

Scientific rationale for traditional use of plants to treat tuberculosis in the eastern region of the OR Tambo district, South Africa

ETHNOPHARMACOLOGICAL RELEVANCE

Tuberculosis (TB) remains a major health problem for humans worldwide, and was responsible for 1.4 million human deaths in 2015 alone. Although there is treatment for TB, emerging multi-drug, extensively drug and totally drug resistant forms of this disease, as well as co-infection with human immunodefiency virus (HIV) continue to worsen the situation. South Africa is among countries with reported traditional use and published documentation of such knowledge concerning the use of plants against TB. Based on a previous study where plants used traditionally for treating TB in the eastern region of OR Tambo district, South Africa, were documented, the present study aimed to determine the antimycobacterial effect, cytotoxicity and genotoxicity of plants selected from that list.

MATERIAL AND METHODS

Acetone, 70% ethanol, cold and hot water extracts were tested for antimycobacterial activity against saprophytic Mycobacterium species including M. aurum, M. bovis BCG, M. gordonae, M. fortuitum, and M. smegmatis using a microdilution method. Extracts with MIC values less than 1 mg/ml against at least three Mycobacterium strains were evaluated for antimycobacterial activity against pathogenic Mycobacterium strains including M. tuberculosis H37RV, M. tuberculosis and M. bovis, cytotoxicity (against Vero monkey kidney and bovine dermis cells), and genotoxicity (against Salmonella typhimurium TA98 and TA100).

RESULTS

The MIC values of the extracts ranged from 0.02 to 2.50 mg/ml, LC₅₀ values of twenty-nine extracts ranged from 0.001 to > 1 mg/ml and the highest selectivity index was 79.50, an extremely promising value. Phymaspermum acerosum roots and leaves (ethanol and water) extracts had the best MIC value (0.02 mg/ml) against at least one Mycobacterium strain. It was interesting to note the lack of cytotoxicity of these extracts with the highest selectivity index value of 39.75. Pterocelastrus echinatus bark acetone and Protorhus longifolia leaf hot water extracts were the most cytotoxic with LC₅₀ = 0.001 and 0.008 mg/ml, respectively, whereas Pittosporum viridiflorum bark water extract was genotoxic. Among non-pathogenic strains, M. gordonae, M. aurum, M. smegmatis showed good correlation of activity with pathogenic M. tuberculosis H37Rv, M. tuberculosis and M. bovis, however, M. aurum was the best predictor with Mycobacterium tuberculosis H37Rv (correlation coefficient value = 0.73).

CONCLUSION

The results indicate that Heteromorpha trifoliata and Phymaspermum acerosum should be investigated further for antimycobacterial efficacy against drug resistant strains of Mycobacterium.

Polygonatum sibiricum rhizome promotes sleep by regulating non-rapid eye movement and GABAergic/serotonergic receptors in rodent models

The aim of this study is to investigate the sleep-promoting effect of a water extract of the Polygonatum sibiricum rhizome (PSE) in rodent models. PSE contained oleamide (0.10 mg/g extract) and glyceryl monolinoleate (0.17 mg/g extract), which are recognized as sleep-promoting substances. In pentobarbital-induced sleep model at hypnotic level, PSE (160 mg/kg) administration significantly decreased sleep latency time by 29% (2.7 min) and increased sleep duration time by 70% (68.4 min) compared with the normal control (3.8 min and 40.7 min, respectively). In the electroencephalography (EEG) analysis of rats, PSE-mediated sleep promotion accompanied the change of sleep architecture including increase of non-rapid eye movement (NREM) and decrease of REM. This sleep promoting effect was more obvious in caffeine-induced awakening model; total sleep time was increased by 40% along with increased NREM by PSE treatment at 160 mg/kg. In addition, PSE significantly increased the protein and mRNA levels of GABA_A-R2 and 5-HT1A receptor, the major sleep-related neurotransmitter receptors. Furthermore, glyceryl monolinoleate and oleamide effectively bound to GABA_A receptor in a competitive binding assay. These results indicate that PSE-mediated sleep-promoting effect is associated with the extension of NREM and upregulation of GABA_A-R2 and 5-HT1A, and is mediated by binding to the GABA_A receptor in vertebrate models.

Effect of Valerian/Hop Mixture on Sleep-Related Behaviors in Drosophila melanogaster

The aim of this study was to investigate the sleep-promoting effect of a Valerian/Hops mixture in fruit flies. The HPLC analysis showed that Valerenic acid (1260.53 µg/g of extract) and Xanthohumol (Cascade: 827.49 µg/g, Hallertau: 763.60 µg/g, Saaz: 186.93 µg/g) were contained in Valerian and Hop, respectively. The sleep patterns of fruit flies on the Valerian/Hops were examined in both baseline and caffeine-treated conditions. Total activities of flies significantly decreased in 20 mg/mL Valerian (74%), 10 mg/mL Cascade (25%), and 5 mg/mL Hallertau (11%) during nighttime or daytime compared with the control. Valerian/Cascade mixture showed longer sleeping time (ca. 20%) than control group. This mixture-mediated effect was partly observed in caffeine-treated flies. Valerian/Cascade mixture upregulated mRNA expressions of gamma-aminobutyric acid (GABA) receptors and serotonin receptor, and GABA receptors were more strongly regulated than serotonin receptor. In competitive GABA receptor binding assay, Valerian/Cascade mixture extract showed a higher binding ability on GABA receptor than Valerenic acid or/and Xanthohumol which are estimated to be active compounds in the extract. This study demonstrates that a Valerian/Cascade mixture extract improves sleep-related behaviors, including sleeping time, by modulating GABAergic/serotonergic signaling.

The effects of herbal medicine on epilepsy

Traditional herbal medicine plays a significant role in the treatment of epilepsy. Though herbal medicine is widely used in antiepileptic treatment, there is a lack of robust evidence for efficacy and toxicity of most herbs. Besides, the herbal medicine should be subject to evidence-based scrutiny. In this context, we present a review to introduce the effects of herbal medicine on epilepsy. However, hundreds of herbal medicines have been investigated in the available studies. Some commonly used herbal medicines for epilepsy have been listed in our study. The overwhelming majority of these data are based on animal experiments. The lack of clinical data places constraints on the clinical recommendation of herbal medicine. Our study may conduct further studies and provide some insight on the development of anti-epileptic drugs.

Romaine Lettuce/Skullcap Mixture Improves Sleep Behavior in Vertebrate Models

The aim of this study is to investigate the effects of romaine lettuce leaves extract (RE), skullcap root extract (SE) and their mixture on sleep behaviors in vertebrate models. HPLC analysis showed that RE contains lactucopicrin (0.02±0.01 mg/g extract), chlorogenic acid (4.05±0.03 mg/g extract), caffeic acid (2.38±0.03 mg/g extract), and chicoric acid (7.02±0.32 mg/g extract) as main phenolic compounds, while SE includes baicalin (99.4±0.5 mg/g extract), baicalein (8.28±0.21 mg/g extract), and wogonin (3.09±0.32 mg/g extract). The mixture of RE (100 mg/g extract) and SE (40 mg/g extract) increased total sleep time by 50.9% compared with the control in pentobarbital-induced sleep model. In electroencephalography (EEG) analysis, RE/SE mixture significantly increased Non-Rapid Eye Movement (NREM), in which delta wave was enhanced by around 40% compared with normal control, leading to the increase of sleep time. In caffeine-induced wake model, RE/SE mixture greatly decreased (53%) caffeine-induced wake time, showing a similar level to normal control. In addition, caffeine-induced decreased of NREM and delta wave effectively increased with RE/SE mixture; NREM and delta wave increased by 85% and 108%, respectively. Furthermore, RE/SE mixture was shown to bind to a gamma-aminobutyric acid type A (GABAA)-benzodiazepine (BZD) receptor stronger than RE or SE single extract. Taken together, RE/SE mixture effectively improved sleep behavior with the increase of NREM via GABAA-BZD receptor binding. RE/SE mixture can be used as an herbal agent for sleep disorders.

Phytochemical and biological investigations of Amaryllidaceae alkaloids: a review

Amaryllidaceae is a family that includes 75 genera and about 1100 species, which have a long history of medicinal use. Many plants have been proven to possess efficacy for neurological injury and inflammatory conditions. This article summarizes 357 Amaryllidaceae alkaloids, and cites 166 174 references over the last three decades. These alkaloids are classified into 14 skeleton types, and their abundant sources are also included. Modern pharmacology studies demonstrate that alkaloids that exclusively occur in Amaryllidaceae plant possess wide-ranging pharmacological actions, especially effects on the central nervous system, as well as antitumor, antimicrobial, and anti-inflammatory activities. Effective monomeric compounds from Amaryllidaceae screened for pharmacological activity in vivo and in vitro are also summarized.

A pharmacological basis of herbal medicines for epilepsy

Epilepsy is the most common chronic neurological disease, affecting about 1% of the world's population during their lifetime. Most people with epilepsy can attain a seizure-free life upon treatment with antiepileptic drugs (AEDs). Unfortunately, seizures in up to 30% do not respond to treatment. It is estimated that 90% of people with epilepsy live in developing countries, and most of them receive no drug treatment for the disease. This treatment gap has motivated investigations into the effects of plants that have been used by traditional healers all over the world to treat seizures. Extracts of hundreds of plants have been shown to exhibit anticonvulsant activity in phenotypic screens performed in experimental animals. Some of those extracts appear to exhibit anticonvulsant efficacy similar to that of synthetic AEDs. Dozens of plant-derived chemical compounds have similarly been shown to act as anticonvulsants in various in vivo and in vitro assays. To a significant degree, anticonvulsant effects of plant extracts can be attributed to widely distributed flavonoids, (furano)coumarins, phenylpropanoids, and terpenoids. Flavonoids and coumarins have been shown to interact with the benzodiazepine site of the GABAA receptor and various voltage-gated ion channels, which are targets of synthetic AEDs. Modulation of the activity of ligand-gated and voltage-gated ion channels provides an explanatory basis of the anticonvulsant effects of plant secondary metabolites. Many complex extracts and single plant-derived compounds exhibit antiinflammatory, neuroprotective, and cognition-enhancing activities that may be beneficial in the treatment of epilepsy. Thus, botanicals provide a base for target-oriented antiepileptic drug discovery and development. In the future, preclinical work should focus on the characterization of the effects of plant extracts and plant-derived compounds on well-defined targets rather than on phenotypic screening using in vivo animal models of acute seizures. At the same time, available data provide ample justification for clinical studies with selected standardized botanical extracts and plant-derived compounds. This article is part of a Special Issue entitled "Botanicals for Epilepsy".

A model on how to obtain data from botanical practitioners

OBJECTIVE

This paper addresses the challenge on how to obtain information from practitioners with experience in using medicinal plants.

BACKGROUND

Collecting information on medicinal uses of plants is very challenging; since botanical remedies are used within the context of multiple differing medical systems, practitioners differ in training from Western physicians and scientists, and active ingredients of botanicals vary with preparation method, growth, and harvest conditions.

DESIGN/METHODS

A model on how useful data on safety and efficacy can be obtained from botanical practitioners is presented, based on methods developed by the association of anthroposophic physicians in Europe, a system of integrative medicine which includes the use of botanicals and is practiced mostly by medical doctors.

RESULTS

Decades of experience by hundreds of practitioners are summarized and made accessible in a manual, which alphabetically lists the most commonly used botanicals and describes the most successful therapeutic experiences which could be confirmed by several of the contributing practitioners.

CONCLUSIONS/RELEVANCE

This approach of continuous, multilingual systematic collection of successful therapeutic experiences within a community of practitioners with similar goals and a common therapeutic framework can be used not only for the training of successful future botanical practitioners, but also for helping to identify promising botanicals for scientific research and to further their development, and could support their official registration with governing bodies in countries of their use. This article is part of a Special Issue entitled "Botanicals for Epilepsy".

The importance of botanical treatments in traditional societies and challenges in developing countries

Epilepsy is one of the most common neurological conditions worldwide, with many affected persons found in Asia, Latin America, and sub-Saharan Africa. Relatedly, the large majority found in these regions does not receive the appropriate therapy with antiepileptic drugs (AEDs), stemming from various reasons among which are lack of access to AEDs, social stigma, and negative cultural attitudes. The presence of epilepsy resistant to the available AEDs coupled with the frequent AED side effects has further fueled the widespread and growing use of botanicals as alternative therapy in several traditional societies in these developing countries since people with epilepsy (PWE) consider them as safe and effective. There have, however, been few botanicals that have been examined for their pharmacological activities related to traditional uses, and there is hardly any conclusive evidence regarding their efficacy in humans or knowledge about the exact mechanism(s) of action. This review discusses some botanical treatments that have been used for epilepsy in developing countries and the challenges faced. This article is part of a Special Issue entitled "Botanicals for Epilepsy".

Polarity of extracts and fractions of four Combretum (Combretaceae) species used to treat infections and gastrointestinal disorders in southern African traditional medicine has a major effect on different relevant in vitro activities

ETHNOPHARMACOLOGICAL IMPORTANCE

Gastrointestinal disorders and infections are the major pathoaetiologies of diarrhoea causing many problems in human health and animal production. Many Combretum species are used in traditional medicine to treat infectious diseases including diarrhoea and many other ailments by rural people in Africa and Asia. Much of the work done to date on this genus was on the non-polar or intermediate polarity components. Some parameters that may cause diarrhoea and the evaluation of more polar extracts have apparently not been investigated.

AIMS

The polar components were extracted and fractionated by solvent-solvent fractionation to yield fractions with different polarities. The activity of these fractions on different parameters that could be involved in factors associated with diarrhoea was investigated. The cytotoxic activities of the extracts were also determined to evaluate the potential of these extracts to combat diarrhoea in production animals.

MATERIALS AND METHODS

Phenolic-enriched leaf extracts of Combretum bracteosum (COB), Combretum padoides (COP), Combretum vendae (COV) and Combretum woodii (COW) were obtained by extracting with a mixture of 70% acetone acidified with 1% HCl and n-hexane. Acetone was removed from a portion of the 70% acetone extract and it was sequentially treated by solvent-solvent fractionation with dichloromethane, ethyl acetate, and butanol to yield fractions with a large variation in polarity. The phenolic constituents of the extracts and fractions were determined using standard procedures The antioxidant activities were determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH); 2,2'-azino-bis (3-ethylbenzothiazoline)-6-sulphonic acid (ABTS(+)) radical scavenging, ferric reducing antioxidant power (FRAP) methods and lipid peroxidation inhibitory capacity standard methods. The ferric reducing antioxidant activities of the fractions were also determined. The minimum inhibitory concentrations (MICs) of the crude extracts and fractions against four bacterial and three fungal strains were assessed with a microplate serial dilution method. Cyclooxygenase (COX) and lipoxygenase (LOX) enzyme inhibitory assays and cytotoxicity studies against Vero cells were also carried out.

RESULT

Some of the fractions had much higher antioxidant activity than the positive controls. The average EC50 values of the extracts for the DPPH and ABTS antioxidant assays were 0.21-12µg/ml (COP), 0.25-16µg/ml (COV), 0.33-9.41µg/ml (COW) and 4.97-85µg/ml (COB) respectively while the mean EC50 values for the positive controls ascorbic acid and trolox were 1.28-1.51 and 1.02-1.19µg/ml respectively. All the crude extracts inhibited lipid peroxidation of linoleic acid by more than 80% at a concentration of 64 µg/ml. COP had the highest antibacterial activity with MICs ranging between 19-2500µg/ml, followed by COV with MICs ranging between 39-625µg/ml; COW and COB had similar MICs ranging between 39-2500µg/ml. COP also had the highest antifungal activity with MICs between 19-625µg/ml. The MIC for COW and COV ranged from 19 to 1250 µg/ml. COB had the lowest antifungal activity (MIC values were between 39 and 625 µg/ml). In general non-polar fractions had a high antimicrobial activity and polar fractions had a high antioxidant activity. The extracts had no activity against COX 1 and 2 enzymes in the anti-inflammatory assay but had good lipoxygenase inhibition. The crude extracts had high concentration of hydrolysable tannin (gallotannin). A good correlation (R(2)= 0.99) was found between the antioxidant activity and total tannin content indicating that, gallotannins may be responsible for the antioxidant activity.

CONCLUSION

The results obtained in this study with more polar extracts indicate that the use of extracts of these plant species as antidiarrhoeal agents may have a scientific basis. The extractant used here extracted a much higher percentage of the phytochemicals than acetone. It was better for isolating antioxidant compounds (polar) but not good for isolating antimicrobial compounds (non-polar) from the same species compared to acetone, ethyl acetate, dichloromethane, and hexane.

Traditional usage, phytochemistry and pharmacology of the South African medicinal plant Boophone disticha (L.f.) Herb. (Amaryllidaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Boophone disticha is the most common member of the South African Amaryllidaceae used extensively in traditional medicine of the various indigenous population groups, including the Sotho, Xhosa and Zulu as well as the San. This survey was carried out to identify and highlight areas relevant to the traditional usage of Boophone disticha. Pharmacological aspects were examined with the purpose of reconciling these with the traditional usage of the plant. In relation to phytochemical make-up, particular attention was paid on how its alkaloid constitution might corroborate the various biological effects manifested by the plant.

MATERIALS AND METHODS

Information gathering involved the use of four different database platforms, including Google Scholar, ScienceDirect, SciFinder(®) and Scopus. Arrangement and detailing of this information is as reflected in the various sections of the paper.

RESULTS

Sixteen categories were identified under which Boophone disticha finds use in traditional medicine. These were shown to include general usage purposes, such as 'cultural and dietary', 'well-being', 'personal injury', 'divinatory purposes', 'psychoactive properties' and 'veterinary uses'. Furthermore, traditional usage was seen to involve six body systems, including functions pertaining to the circulatory, gastrointestinal, muscular, neurological, respiratory and urinary systems. The four remaining categories relate to use for inflammatory conditions, cancer, malaria and tuberculosis. Overall, three areas were discernible in which Boophone disticha finds most usage, which are (i) ailments pertaining to the CNS, (ii) wounds and infections, and (iii) inflammatory conditions. In addition, several aspects pertaining to the toxic properties of the plant are discussed, including genotoxicity, mutagenicity and neurotoxicity.

CONCLUSION

The widespread ethnic usage of Boophone disticha has justified its standing as a flagship for the Amaryllidaceae and its relevance to South African traditional medicine. Furthermore, its promising pharmacological and phytochemical profiles have stimulated significant interest in the clinical realm, especially in the areas of cancer and motor neuron disease chemotherapy. These collective properties should prove useful in steering the progress of the plant towards a wider audience.

Hypoxis (Hypoxidaceae) in African traditional medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Hypoxis species (Hypoxidaceae) are popular medicinal plants used in the African traditional medicine to treat numerous ailments and are reported to have a wide spectrum of pharmacological properties. In this paper we reviewed and evaluated the traditional uses, pharmacological, phytochemistry and toxicity aspects of the genus Hypoxis. Potential medicinal prospects and possible knowledge gaps and pitfalls are discussed.

MATERIALS AND METHODS

A comprehensive and systematic review of literature on Hypoxis species was done using numerous resources such as books and scientific databases that include Pubmed, Scopus, Scirus, Google scholar, Web of Science and others. Information on the various pharmacological and chemical properties of Hypoxis extracts was critically analysed and discussed under the various topics.

RESULTS

The literature indicated a broad range of uses, pharmacological and toxicological properties of different Hypoxis species extracts and their relevance to African healthcare systems. Several compounds, mostly glucosides, sterols and sterolins, have been isolated, identified and tested in various in vitro and in vivo models as well as in a couple of clinical trials with a lot of promising prospects reported in some studies.

CONCLUSION

A critical analysis of the available literature and studies identifies positive potential for the future use of Hypoxis species in both traditional and modern medicine and concurrently so with possible pitfalls and research gaps in current knowledge. An integrated and holistic approach to addressing research issues, particularly toxicology aspects could be more effectively applied and incorporate conservation strategies for the species.

Rhus parviflora and its biflavonoid constituent, rhusflavone, induce sleep through the positive allosteric modulation of GABA(A)-benzodiazepine receptors

ETHNOPHARMACOLOGICAL RELEVANCE

Rhus parviflora is referred as 'Tintidikah' in traditional medicinal system of south Asia (Ayurveda). It is used in treatment of Vāta vikāra, a condition related to neurological complications as well as cure for stomach disorders.

MATERIALS AND METHODS

Dried and powdered fruits of R. parviflora were extracted with 80% aqueous methanol (RPME). The concentrated extract was successively partitioned with distilled water (DW), ethyl acetate (EtOAc), and n-butanol (n-BuOH). All extracts, as well as isolated biflavonoids from R. parviflora, were evaluated for their affinity to the benzodiazepine binding site of GABA(A) receptor. The sedative-hypnotic effects of the fractions were evaluated by measuring sleep latency and sleep duration during pentobarbital-induced sleep in mice after oral administration of the extract fractions.

RESULTS

Oral administration of RPME (125 mg/kg, 250 mg/kg, 500 mg/kg, and 1000 mg/kg) produced a dose-dependent decrease in sleep latency and an increase in sleep duration in mice treated with pentobarbital. The methanol extract produced a hypnotic effect that was fully blocked by ³H-Ro 15-1788 flumazenil (FLU). Further, among the solvent fractions, the ethyl acetate fraction exhibited significant activity. Among the isolated compounds, biflavonoids mesuaferrone B (1), rhusflavone (3), and agathisflavone (4) competitively inhibited FLU binding with a K(i) of 0.280 μM, 0.045 μM, and 0.091 μM, respectively. In addition, analysis of the sedative-hypnotic effects of rhusflavone, as well as those of the ethyl acetate, n-butanol, and distilled water fractions revealed that the modulation of both the ethyl acetate fraction and biflavonoid rhusflavone (3) are the most potent in inducing sleep.

CONCLUSION

The presence of conjugated ketone and C6-C8″ biflavonoid linkage in rhusflavone may be responsible for BZD-site of the GABA(A) leading to decrease in sleep latency and increase sleep duration.

Investigation into the genotoxicity of water extracts from Hypoxis species and a commercially available Hypoxis preparation

We performed an in vitro evaluation of the genotoxic potential of water extracts from four Hypoxis species (Hypoxis hemerocallidea, H. colchicifolia, H. rigidula, H. acuminata) and a commercial preparation thereof using the neutral red uptake (NRU) assay, the alkaline comet assay and the cytome assay in human hepatoma HepG2 cells. The relative cytotoxicity of these samples was established by determining their NI50 values (50% inhibition of NRU), and these results were used for dose-finding in genotoxicity tests. None of the tested extracts were identified as genotoxic in both the alkaline comet assay and cytome assay.

Depressive effects on the central nervous system and underlying mechanism of the enzymatic extract and its phlorotannin-rich fraction from Ecklonia cava edible brown seaweed

Marine plants have been reported to possess various pharmacological properties; however, there have been few reports on their neuropharmacological effects. Terrestrial plants have depressive effects on the central nervous system (CNS) because of their polyphenols which make them effective as anticonvulsants and sleep inducers. We investigated in this study the depressive effects of the polyphenol-rich brown seaweed, Ecklonia cava (EC), on CNS. An EC enzymatic extract (ECEE) showed significant anticonvulsive (>500 mg/kg) and sleep-inducing (>500 mg/kg) effects on the respective mice seizure induced by picrotoxin and on the mice sleep induced by pentobarbital. The phlorotannin-rich fraction (PTRF) from ECEE significantly potentiated the pentobarbital-induced sleep at >50 mg/kg. PTRF had binding activity to the gamma aminobutyric acid type A (GABA(A))-benzodiazepine (BZD) receptors. The sleep-inducing effects of diazepam (DZP, a well-known GABA(A)-BZD agonist), ECEE, and PTRF were completely blocked by flumazenil, a well-known antagonist of GABA(A)-BZD receptors. These results imply that ECEE produced depressive effects on CNS by positive allosteric modulation of its phlorotannins on GABA(A)-BZD receptors like DZP. Our study proposes EC as a candidate for the effective treatment of neuropsychiatric disorders such as anxiety and insomnia.

Isoliquiritigenin, a chalcone compound, is a positive allosteric modulator of GABAA receptors and shows hypnotic effects

Isoliquiritigenin (ILTG) is a chalcone compound and has valuable pharmacological properties such as antioxidant, anti-inflammatory, anticancer, and antiallergic activities. Recently, the anxiolytic effect of ILTG has been reported; however, its action mechanism and hypnotic activity have not yet been demonstrated. Therefore, we investigated the hypnotic effect and action mechanism of ILTG. ILTG significantly potentiated the pentobarbital-induced sleep in mice at doses of 25 and 50mg/kg. The hypnotic activity of ILTG was fully inhibited by flumazenil (FLU), a specific gamma-aminobutyric acid type A (GABA(A))-benzodiazepine (BZD) receptor antagonist. The binding affinity of ILTG was 0.453 μM and was found to be higher than that of the reference compound, diazepam (DZP, 0.012 μM). ILTG (10(-5)M) potentiated GABA-evoked currents to 151% of the control level on isolated dorsal raphe neurons. ILTG has 65 times higher affinity for GABA(A)-BZD receptors than DZP, and the dissociation constant for ILTG was 4.0 × 10(-10)M. The effect of ILTG on GABA currents was blocked by 10(-7)M FLU and ZK-93426. These results suggest that ILTG produces hypnotic effects by positive allosteric modulation of GABA(A)-BZD receptors.

South African plants used in traditional medicine to treat epilepsy have an antagonistic effect on NMDA receptor currents

ETHNOPHARMACOLOGICAL RELEVANCE

Several Searsia species (Anacardiaceae), including Searsia dentata and Searsia pyroides, are used in South Africa traditional medicine to treat epilepsy. Ethanol leaf extracts of these plants have been shown to act as possible antagonists of N-methyl-d-aspartate (NMDA)-type glutamate receptors.

MATERIALS AND METHODS

Leaf material of three Searsia species were collected from the Botanical Garden at the University of KwaZulu-Natal, Pietermaritzburg; dried and extracted with ethanol in an ultrasound bath. Filtered and dried extracts were resuspended in DMSO (100mg/ml) and diluted in the recording solution. The effect of Searsia dentata, Searsia pyroides and Searsia glauca extracts was investigated in dissociated cerebellar granule cells (CGCs) from 8-day-old rats and in transiently transfected HEK (human embryonic kidney) 293 cells (HEK), expressing either NR1a/NR2A or NR1a/NR2B receptors. In both systems we measured whole-cell currents elicited by 0.5mM NMDA (CGCs) or 50 μM glutamic acid (HEK) at -60 mV in 0Mg and 30 μM glycine and NMDA driven Ca influx in Fura2-loaded CGC.

RESULTS

Searsia dentata and Searsia pyroides ethanol extracts caused a dose-dependent decrease of NR current with ED(50) close to 0.03 mg/ml in CGC and a similar inhibition (80% with 1mg/ml) in HEK cells, while Searsia glauca was much less effective. The inhibition was dependent on time of incubation and slightly favored by opening of the NR channel. It was hardly reversible during the recording time, but was not caused by accelerated run-down or by interaction with the modulatory redox site. Searsia pyroides ethanol extract also depressed the NMDA stimulated increase in intracellular Ca.

CONCLUSIONS

The data confirm the specificity of Searsia dentata and Searsia pyroides and justify their use in traditional medicine. These plants may combine one or more γ-aminobutyric acid (GABA)(A) agonists with one or more NMDA antagonists, thus representing an efficient treatment for epilepsy.

Phlorotannins of the edible brown seaweed Ecklonia cava Kjellman induce sleep via positive allosteric modulation of gamma-aminobutyric acid type A-benzodiazepine receptor: A novel neurological activity of seaweed polyphenols

The primary objective was to investigate whether seaweeds have hypnotic activity. Methanol extracts of 30 seaweeds were screened for their binding activity at the GABA type A-benzodiazepine (GABA_A-BZD) receptor, a well-characterised molecular target for sedative-hypnotics. The most active seaweed was Ecklonia cava Kjellman (ECK). An ethanol extract of ECK (ECK-E) significantly potentiated pentobarbital-induced sleep in mice. In four solvent fractions separated from ECK-E, hypnotic activity was proportional to contents of total phenols and total phlorotannins, known as seaweed polyphenols. Major phlorotannins of the ethyl acetate (EtOAc) fraction with the highest activity were eckol, eckstolonol, dieckol, and triphlorethol-A, and their K_i (binding affinity, μM) values for [³H]-flumazenil binding were 1.070, 1.491, 3.072, and 4.419, respectively. Hypnotic effects of ECK-E and the EtOAc fraction were fully inhibited by flumazenil, a specific GABA_A-BZD receptor antagonist. These results imply that phlorotannins of ECK induce sleep by positive allosteric modulation of the GABA_A-BZD receptor.

Hypnotic effects and binding studies for GABA(A) and 5-HT(2C) receptors of traditional medicinal plants used in Asia for insomnia

AIM OF THE STUDY

Many medicinal plants have been used for treatment of insomnia in Asia. However, scientific evidence and precise mechanism for their sedative-hypnotic activity have not been fully investigated. Thus, we investigated the binding activity of the oriental plant extracts (mainly from Korea and Japan) to the well-known molecular targets for sleep regulation, GABA(A) and 5-HT(2C) receptors. Following the binding assay, sedative-hypnotic effects of the extracts with high affinity were examined in an animal model of sleep.

MATERIALS AND METHODS

Aqueous and ethanol extracts of 15 medicinal plants were tested for binding at the benzodiazepine site of GABA(A) receptor and 5-HT site of 5-HT(2C) receptor. The sedative-hypnotic effects of selected extracts were evaluated by measuring the sleep latency and sleep duration during pentobarbital-induced sleep in mice after oral administration of extracts.

RESULTS

In the GABA(A) assay, the ethanol extracts of licorice and danshen displayed concentration-dependent, high affinity binding, whereas in the 5-HT(2C) assay, the ethanol extracts of ginseng and silk tree showed high affinity. Among these extracts we tested previously uncharacterized licorice and silk tree for hypnotic effects. We found the ethanol extracts of licorice and silk tree significantly decreased sleep latency and increased sleep duration in pentobarbital-induced sleep.

CONCLUSIONS

We demonstrate for the first time that licorice and silk tree have the sedative-hypnotic activity possibly by modulating GABA(A) and 5-HT(2C) receptors. We propose that licorice and silk tree might be effective candidates for treatment of insomnia.

Bioassay-guided isolation of apigenin with GABA-benzodiazepine activity from Tanacetum parthenium

Extracts of Tanacetum parthenium are used in the prophylactic treatment of migraine and have also been used in Danish folk medicine for the treatment of epilepsy. An ethanol extract of T. parthenium showed high affinity for the GABA(A)-benzodiazepine site. An ethanol extract of T. parthenium was fractionated by VLC on silica and preparative C18 HPLC. Each step was monitored with the GABA(A)-benzodiazepine bioassay. The fractionation led to the isolation of apigenin, which may be responsible for CNS-effects of T. parthenium extracts.

Plants with neurobiological activity as potential targets for drug discovery

Significant number of studies has been performed to find alternatives or treatments for diseases of the nervous forum by identifying structures with activity at the central nervous system (CNS). However most of the screenings are usually conducted on an ad hoc basis and not systematically. The initial purpose of this review was to screen plants with neurological bioactivity, in particular those that have not been fully studied and that have molecular mechanisms whose active constituents responsible for the activity remain to be identified. The second purpose was to identify potential target plants for future studies of new and alternative therapies for the treatment of neurological disorders and neurodegenerative diseases. All plants considered in this review were selected for three qualities: possible molecular requirements to act at the CNS; representative of the main classes of compounds with the referred bioactivity and the major families containing species with those compounds; and diffuse world distribution. We identified several examples of plants that have potential for further study. We have included the main families of these plants, their known molecular mechanisms involved in neurological bioactivity, and the active constituents responsible for such activity. Also included is a brief discussion about the requirements of the different compounds to reach the CNS. These requirements may be less limited than what researchers have previously thought.

Amides from Piper capense with CNS activity - a preliminary SAR analysis

Piper capense L.f. (Piperaceae) is used traditionally in South Africa as a sleep inducing remedy. Bioassay-guided fractionation of the roots of P. capense led to the isolation of piperine (1) and 4,5-dihydropiperine (2), which showed moderate affinity for the benzodiazepine site on the GABA_A receptor (IC₅₀ values of 1.2 mM and 1.0 mM, respectively). The present study suggests that strict structural properties of the amides are essential for affinity. Taken together, these observations suggest that the carbon chain must contain not less than four carbons, and that a conjugated double bond, adjacent to the amide group, is necessary for binding to the receptor and that the amine part should be bulky.

Pharmacological screening of Malian medicinal plants used against epilepsy and convulsions

ETHNOPHARMACOLOGICAL RELEVANCE

Several medicinal plants are used in Mali to treat epilepsy and convulsions. So far, no studies have investigated the pharmacological effect of these plants.

AIMS

The aim of this study was to investigate the in vitro and in vivo antiepileptic potential of the ethanolic extracts of 11 Malian medicinal plants.

MATERIALS AND METHODS

The extracts were screened for antiepileptic properties in the mouse cortical wedge preparation and in the [3H]-flumazenil binding assay. Two of the plant extracts were investigated for anticonvulsive properties in the pentylenetetrazol (PTZ) kindling model in mice. Possible side effects on motor impairment were evaluated using the rota-rod test.

RESULTS

Extracts of 10 of the 11 medicinal plants showed affinity to the benzodiazepine binding site on the GABAA receptor. Seven of the 11 extracts inhibited the spontaneous discharges (SEDs) in the mouse cortical wedge preparation, with the extracts of Flueggea virosa and Psorospermum senegalense being the most potent. However, when tested for in vivo anticonvulsive properties these two extracts failed to show any effect on PTZ-induced seizures in mice.

CONCLUSIONS

The pharmacological screening of the ethanolic extracts of 11 Malian medicinal plants in vitro lead to the identification of several extracts with potential anticonvulsant properties.

The effect of extracts of Searsia species on epileptiform activity in slices of the mouse cerebral cortex

ETHNOPHARMACOLOGICAL RELEVANCE

Searsia dentata and Searsia pyroides are used in traditional South African medicine to treat convulsions and epilepsy. Previous studies have demonstrated that extracts of these plants comprise compounds that bind to the flumazenil-sensitive site on the GABA(A) receptor. However, their use as anticonvulsant medicinal plants cannot be adequately explained by these findings.

AIMS

The aim of this study was to examine the possible involvement of the glutamatergic system of extracts from the plants.

MATERIALS AND METHODS

The mouse cortical wedge preparation was used for functional characterization of the extracts. The affinity towards the NMDA and the AMPA receptor was investigated using classical [(3)H]-GP39653 and [(3)H]-AMPA binding assays, respectively.

RESULTS

The extracts of Searsia dentata and Searsia pyroides inhibited the spontaneous epileptiform discharges in mouse cerebral cortical slices with ED(50) of 0.62 and 1.67mg dry extract/mL, respectively. Both extracts displaced [(3)H]-GP39653 binding and significantly inhibited the NMDA-induced response during co-administration in cortical slices.

CONCLUSION

In this study, the NMDA receptor antagonistic effect of the crude ethanolic extracts of these two South African medicinal plants was demonstrated.

Review on plants with CNS-effects used in traditional South African medicine against mental diseases

The majority of the population in South Africa use traditional health care to treat various mental conditions. In this review, we present ethnobotanical information on plants used by the traditional healers in South Africa to treat mental illnesses, specifically epilepsy, depression, age-related dementia and debilitative mental disorders. Details of the recent scientific studies conducted on some of these plants are reviewed. Extracts of Searsia chirindensis, Cotelydon orbiculata and Leonotis leonurus have shown in vivo anticonvulsant activity. Extracts from Searsia dentata and Searsia pyroides showed spontaneous epileptiform discharge in mouse cortical slices, and acted as NMDA-receptor antagonists. Apigenin, amentoflavone and agathisflavone with affinity to the benzodiazepine site on the GABA(A)-receptor were isolated from Searsia pyroides. Naringenin with affinity to the GABA(A)-benzodiazepine receptor was isolated from Mentha aquatica. Agapanthus campanulatus, Boophone disticha, Mondia whitei and Xysmalobium undulatum exhibited antidepressant-like activity in three in vivo models for depression. Amaryllidaceae alkaloids with activity to the serotonin transporter were isolated from Boophone disticha. The alkaloid mesembrine, which act as a serotonin reuptake inhibitor, was isolated from Sceletium tortuosum. Investigations of plants used to treat age-related dementia and debilitative mental disorders lead to the isolation of a number of Amaryllidaceae alkaloids with acetylcholinesterase inhibitory activity from Boophone disticha and Crinum species. Extracts of Mentha aquatica, Gasteria croucheri, Ruta graveolens and Scotia brachypetala inhibited MAO-B. Naringenin was isolated from Mentha aquatica as a MAO inhibitor. Only a small number of the more than 300 southern African plant species reported to treat or affect the CNS have been scientifically evaluated. Very few of the active compounds have been isolated and identified.

Antioxidant activity and cytotoxicity study of the flavonol glycosides fromBauhinia galpinii

The antioxidant activity of the crude extract and solvent fractions obtained from the leaves of Bauhinia galpinii was evaluated in terms of capacity to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals. The crude extract and the more polar solvent fractions (ethyl acetate and butanol) showed considerable antioxidant activity. The antioxidant potential of the extracts, expressed as EC50, ranged between 28.85 +/- 1.28 microg mL(-1)and 118.16 +/- 6.41 microg mL(-1). L-Ascorbic acid was used as a standard (EC50 = 19.79 +/- 0.14 microM). Bioassay guided fractionation of the two active solvent fractions led to the isolation of three flavonoid glycosides, identified as: quercetin-3-O-galactopyranoside (1), myricetin-3-O-galactopyranoside (2), and 2''-O-rhamnosylvitexin (3). These compounds are reported for the first time from this species. The structures of the compounds were determined on the basis of spectral studies (1H NMR, 13C NMR and MS). Their antioxidant potential was evaluated using a DPPH spectrophotometric assay. Compound 2 had higher and 3 had lower antioxidant activity than L-ascorbic acid. No cytotoxic effects were displayed by compounds 1 and 3, but compound 2 was cytotoxic to Vero cells (LC50 = 74.68 microg mL(-1)) and bovine dermis cells (LC50 = 30.69 microg mL(-1)).

Antiplasmodial and GABA(A)-benzodiazepine receptor binding activities of five plants used in traditional medicine in Mali, West Africa

Extracts of five medicinal plants: Boscia angustifolia, Cissus quadrangularis, Securidaca longipedunculata, Stylosanthes erecta and Trichilia emetica, used traditionally in Malian traditional medicine were screened for in vitro antiplasmodial activity and GABA(A)-benzodiazepine receptor binding activity. Four extracts showed significant antiplasmodial activities, with the dichloromethane extract of leaf of Securidaca longipedunculata being the most active (IC(50) of 7 microg/ml [95% CI: 5-9]). The dichloromethane extract of leaf of Trichilia emetica, in addition to its antiplasmodial activity (IC(50): 12 microg/ml [95% CI: 12-14]), exhibited a good binding activity to the GABA(A)-benzodiazepine receptor, while water and methanol extracts of the same plant did not show any activity. A strong GABA(A)-receptor complex binding activity was observed in the methanol extract of aerial part of Stylosanthes erecta. The results in this study justify some of the traditional indications of the plants investigated and may thus be candidates for Improved Traditional Medicines in Mali.

Screening of plants used in Danish folk medicine to treat epilepsy and convulsions

Aqueous and ethanolic extracts of 42 plants used in Danish folk medicine for the treatment of epilepsy and convulsions, or for inducing sedation, were tested for affinity to the GABA(A)-benzodiazepine receptor in the flumazenil-binding assay. Ethanolic extracts of leaves of Primula elatior and Primula veris and aerial parts of Tanacetum parthenium exhibited good, dose-dependent affinity.

Biflavones from Rhus species with affinity for the GABA(A)/benzodiazepine receptor

In South Africa Rhus pyroides is traditionally used in the treatment of epilepsy. In the present study two biflavonoids with activity in the (3)H-Ro 15-1788 (flumazenil) binding assay were isolated by high pressure liquid chromatography (HPLC) fractionation of the ethanol extract of the leaves from Rhus pyroides. The structures of the two biflavonoids were elucidated by nuclear magnetic resonance spectroscopy (NMR) to be agathisflavone and amentoflavone. Agathisflavone and amentoflavone competitively inhibited the binding of (3)H-Ro 15-1788 with a K(i) of 28 and 37 nM, respectively. Extracts of Rhus dentata and Rhus pentheri were not as active as the extract from Rhus pyroides; both were found to contain apigenin and agathisflavone. The monomer apigenin, agathisflavone and amentoflavone were fitted into a pharmacophore model for ligands binding to the GABA(A) receptor benzodiazepine site. This reflected the affinities of the compounds in the [(3)H]-flumazenil binding assay.

Activity of traditional South African sedative and potentially CNS-acting plants in the GABA-benzodiazepine receptor assay

Several plants are traditionally used to treat mental diseases in South Africa. Forty-six ethanol extracts from 35 species, both indigenous and exotic that are traditionally used predominantly as sedatives or to treat various CNS-related ailments were tested in the GABAA-benzodiazepine receptor-binding assay. In this assay, the binding of 3H-Ro 15-1788 (flumazenil) to the benzodiazepine site is measured. The GABAA-benzodiazepine receptor complex is involved in sedation, epilepsy and convulsions. Out of the 46 extracts tested, seven showed good activity and 10 showed moderate activity. The most active extracts were the ethanolic leaf extracts of Arctopus echinatus, Artemisa afra, four Helichrysum species and Mentha aquatica which all showed good dose-dependent activity.